The LM95214 device is an 11-bit digital temperature sensor with a 2-wire System Management Bus (SMBus) interface that can very accurately monitor the temperature of four remote diodes as well as its own temperature. The four remote diodes can be external devices such as microprocessors, graphics processors that target the ideality of a 2N3904 transistor or diode-connected 2N3904s.
The LM95214 reports temperature in two different formats for +127.875°C/–128°C range and 0°C/255°C range. The LM95214 TCRIT1, TCRIT2 and TCRIT3 outputs are triggered when any unmasked channel exceeds its corresponding programmable limit and can be used to shutdown the system, to turn on the system fans or as a microcontroller interrupt function. The current status of the TCRIT1, TCRIT2, and TCRIT3 pins can be read back from the status registers. Mask registers are available for further control of the TCRIT outputs.
Two LM95214 remote temperature channels have programmable digital filters while the other two remote channels use a fault-queue to minimize unwanted TCRIT events when temperature spikes are encountered.
For optimum flexibility and accuracy, each LM95214 channel includes registers for offset correction. A three-level address pin allows connection of up to 3 LM95214s to the same SMBus master. The LM95214 includes power saving functions such as: programmable conversion rate, shutdown mode, and disabling of unused channels.
PART NUMBER | PACKAGE | BODY SIZE (NOM) |
---|---|---|
LM95214 | WSON (14) | 4.00 mm × 4.00 mm |
Changes from A Revision (March 2013) to B Revision
Changes from * Revision (March 2013) to A Revision
PIN | DESCRIPTION | ||
---|---|---|---|
NO. | NAME | ||
1 | NC | No Connect Not connected. May be left floating, connected to GND or VDD. |
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2 | VDD | Positive Supply Voltage Input DC Voltage from 3.0 V to 3.6 V. VDD must be bypassed with a 0.1-µF capacitor in parallel with 100 pF. The 100-pF capacitor must be placed as close as possible to the power supply pin. Noise must be kept below 200 mVp-p, a 10-µF capacitor may be required to achieve this. |
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3 | D4+ | Diode Current Source Fourth Diode Anode. Connected to remote discrete diode-connected transistor junction or to the diode-connected transistor junction on a remote IC whose die temperature is being sensed. A capacitor is not required between D4+ and D–. A 100 pF capacitor between D4+ and D– can be added and may improve performance in noisy systems. Float this pin if this thermal diode is not used. |
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4 | D3+ | Diode Current Source Third Diode Anode. Connected to remote discrete diode-connected transistor junction or to the diode-connected transistor junction on a remote IC whose die temperature is being sensed. A capacitor is not required between D3+ and D–. A 100-pF capacitor between D3+ and D– can be added and may improve performance in noisy systems. Float this pin if this thermal diode is not used. |
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5 | D− | Diode Return Current Sink All Diode Cathodes. Common D– pin for all four remote diodes. |
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6 | D2+ | Diode Current Source Second Diode Anode. Connected to remote discrete diode-connected transistor junction or to the diode-connected transistor junction on a remote IC whose die temperature is being sensed. A capacitor is not required between D2+ and D–. A 100-pF capacitor between D2+ and D– can be added and may improve performance in noisy systems. Float this pin if this thermal diode is not used. |
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7 | D1+ | Diode Current Source First Diode Anode. Connected to remote discrete diode-connected transistor junction or to the diode-connected transistor junction on a remote IC whose die temperature is being sensed. A capacitor is not required between D1+ and D–. A 100-pF capacitor between D1+ and D– can be added and may improve performance in noisy systems. Float this pin if this thermal diode is not used. |
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8 | GND | Power Supply Ground -- System low noise ground. | |
9 | A0 | Digital Input SMBus slave address select pin. Selects one of three addresses. Can be tied to VDD, GND, or to the middle of a resistor divider connected between VDD and GND. |
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10 | TCRIT1 | Digital Output, Open-Drain Critical temperature output 1. Requires pullup resistor. Active LOW. |
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11 | TCRIT2 | Digital Output, Open-Drain Critical temperature output 2. Requires pullup resistor. Active LOW. |
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12 | SMBDAT | SMBus Bidirectional Data Line, Open-Drain Output From and to Controller; may require an external pullup resistor |
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13 | SMBCLK | SMBus Clock Input From Controller; may require an external pullup resistor |
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14 | TCRIT3 | Digital Output, Open-Drain Critical temperature output 3. Requires pullup resistor. Active LOW. |
PIN NO. | LABEL | CIRCUIT | CIRCUITS FOR PIN ESD PROTECTION STRUCTURE |
---|---|---|---|
1 | NC | – | |
2 | VDD | A | |
3 | D4+ | A | |
4 | D3+ | A | |
5 | D- | A | |
6 | D2+ | A | |
7 | D1+ | A | Circuit A |
8 | GND | – | |
9 | A0 | B | |
10 | TCRIT1 | B | |
11 | TCRIT2 | B | |
12 | SMBDAT | B | |
13 | SMBCLK | B | |
14 | TCRIT2 | B | Circuit B |
MIN | MAX | UNIT | ||
---|---|---|---|---|
Supply voltage | –0.3 | 6 | V | |
Voltage at SMBDAT, SMBCLK, TCRIT1, TCRIT2, TCRIT3 |
–0.5 | 6 | V | |
Voltage at other pins | –0.3 | VDD + 0.3 | V | |
D− Input current | ±1 | mA | ||
Input current at all other pins (2) | ±5 | mA | ||
Package input current (2) | 30 | mA | ||
SMBDAT, TCRIT1, TCRIT2, TCRIT3 output sink current |
10 | mA | ||
Storage temperature, Tstg | –65 | 150 | °C |
VALUE | UNIT | |||
---|---|---|---|---|
V(ESD) | Electrostatic discharge(3) | Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) | ±2000 | V |
Charged-device model (CDM), per JEDEC specification JESD22-C101(2) | ±1000 | |||
Machine Model | ±200 |
MIN | NOM | MAX | UNIT | ||
---|---|---|---|---|---|
Operating temperature | –40 | 140 | °C | ||
Supply voltage (VDD) | 3 | 3.6 | V |
THERMAL METRIC(1) | LM95214 | UNIT | |
---|---|---|---|
NHL (WSON) | |||
14 PINS | |||
RθJA | Junction-to-ambient thermal resistance | 38.7 | °C/W |
RθJC(top) | Junction-to-case (top) thermal resistance | 27.5 | °C/W |
RθJB | Junction-to-board thermal resistance | 16.7 | °C/W |
ψJT | Junction-to-top characterization parameter | 0.3 | °C/W |
ψJB | Junction-to-board characterization parameter | 16.6 | °C/W |
RθJC(bot) | Junction-to-case (bottom) thermal resistance | 3.2 | °C/W |
PARAMETER | TEST CONDITIONS | MIN | TYP | MAX | UNIT | ||
---|---|---|---|---|---|---|---|
Temperature error using local diode | TA = –40°C to +125°C, (1) | –2 | ±1 | +2 | °C | ||
Temperature error using an MMBT3904 transistor remote diode(2) | TA = +25°C to +85°C TD = +60°C to +100°C |
–1.1 | +1.1 | °C | |||
TA = +25°C to +85°C TD = –40°C to +125°C |
–1.3 | +1.3 | °C | ||||
TA = –40°C to +85°C TD = –40°C to +125°C |
–3 | +3 | °C | ||||
TA = –40°C to +85°C TD = 125°C to +140°C |
–3.3 | +3.3 | °C | ||||
Local diode measurement resolution | 11 | Bits | |||||
0.125 | °C | ||||||
Remote diode measurement resolution | Digital filter off | 11 | Bits | ||||
0.125 | °C | ||||||
Digital filter on (Remote Diodes 1 and 2 only) | 13 | Bits | |||||
0.03125 | °C | ||||||
Conversion time of all temperatures at the fastest setting(4) | All channels are enabled in default state | 1100 | 1210 | ms | |||
1 external channel | 31 | 34 | ms | ||||
Local only | 30 | 33 | ms | ||||
Quiescent current (3) | SMBus inactive, 1-Hz conversion rate, channels in default state | 570 | 800 | µA | |||
Shutdown | 360 | µA | |||||
D− Source voltage | 0.4 | V | |||||
Remote diode source current | High level | 160 | 230 | µA | |||
Low level | 10 | ||||||
Power-On reset threshold | Measured on VDD input, falling edge | 1.6 | 2.8 | V | |||
TCRIT1 pin temperature threshold | Default diodes 1 and 2 only | 110 | °C | ||||
TCRIT2 pin temperature threshold | Default all channels | 85 | °C | ||||
TCRIT3 pin temperature threshold | Default diodes 3 and 4 only | 85 | °C |
PARAMETER | TEST CONDITIONS | MIN | TYP | MAX | UNIT | ||
---|---|---|---|---|---|---|---|
SMBDAT, SMBCLK INPUTS | |||||||
VIN(1) | Logical 1 input voltage | 2.1 | V | ||||
VIN(0) | Logical 0 input voltage | 0.8 | V | ||||
VIN(HYST) | SMBDAT and SMBCLK digital input hysteresis | 400 | mV | ||||
IIN(1) | Logical 1 input current | VIN = VDD | 0.005 | 10 | µA | ||
IIN(0) | Logical 0 input current | VIN = 0 V | −0.005 | –10 | µA | ||
CIN | Input capacitance | 5 | pF | ||||
A0 DIGITAL INPUT | |||||||
VIH | Input high voltage | 0.90 × VDD | V | ||||
VIM | Input middle voltage | 0.43 × VDD | 0.57 × VDD | V | |||
V | |||||||
VIL | Input low voltage | 0.10 × VDD | V | ||||
IIN(1) | Logical 1 input current | VIN = VDD | VIN = VDD | –0.005 | –10 | µA | |
IIN(0) | Logical 0 input current | VIN = 0 V | VIN = 0 V | 0.005 | 10 | µA | |
CIN | Input capacitance | 5 | pF | ||||
SMBDAT, TCRIT1, TCRIT2, TCRIT3 DIGITAL OUTPUTS | |||||||
IOH | High level output current | VOH = VDD | 10 | µA | |||
VOL(SMBDAT) | SMBus low level output voltage | IOL = 4 mA | 0.4 | V | |||
IOL = 6 mA | 0.6 | V | |||||
VOL(TCRIT) | TCRIT1, TCRIT2, TCRIT3 low level output voltage | IOL = 6 mA | 0.4 | V | |||
COUT | Digital output capacitance | 5 | pF |
PARAMETER | TEST CONDITIONS | MIN | TYP | MAX | UNIT | ||
---|---|---|---|---|---|---|---|
fSMB | SMBus clock frequency | 10 | 100 | kHz | |||
tLOW | SMBus clock low time | from VIN(0)max to VIN(0)max | 4.7 | µs | |||
25 | ms | ||||||
tHIGH | SMBus clock high time | from VIN(1)min to VIN(1)min | 4.0 | µs | |||
tR,SMB | SMBus rise time | See (1) | 1 | µs | |||
tF,SMB | SMBus fall time | See (2) | 0.3 | µs | |||
tOF | Output fall time | CL = 400 pF, IO = 3 mA(2) |
250 | ns | |||
tTIMEOUT | SMBDAT and SMBCLK time low for reset of serial interface | 25 | 35 | ms | |||
tSU;DAT | Data in setup time to SMBCLK high | 250 | ns | ||||
tHD;DAT | Data out stable after SMBCLK low | 300 | 1075 | ns | |||
tHD;STA | Start condition SMBDAT low to SMBCLK low (Start condition hold before the first clock falling edge) | 100 | ns | ||||
tSU;STO | Stop condition SMBCLK high to SMBDAT low (Stop condition setup) | 100 | ns | ||||
tSU;STA | SMBus repeated start-condition setup time, SMBCLK high to SMBDAT low | 0.6 | µs | ||||
tBUF | SMBus free time between stop and start conditions | 1.3 | µs |
The LM95214 is an 11-bit digital temperature sensor with a 2-wire System Management Bus (SMBus) interface that can monitor the temperature of four remote diodes as well as its own temperature. The LM95214 can be used to very accurately monitor the temperature of up to four external devices such as microprocessors, graphics processors or diode-connected 2N3904 transistor. Any device whose thermal diode can be modeled by an MMBT3904 transistor will work well with the LM95214.
The LM95214 reports temperature in two different formats for +127.875°C/–128°C range and 0°C/255°C range. The LM95214 has a Sigma-Delta ADC (Analog-to-Digital Converter) core which provides the first level of noise immunity. For improved performance in a noisy environment the LM95214 includes programmable digital filters for Remote Diode 1 and 2 temperature readings. When the digital filters are invoked the resolution for Remote Diode 1 and 2 readings increases to 0.03125°C. For maximum flexibility and best accuracy the LM95214 includes offset registers that allow calibration of other diode types.
The LM95214 TCRIT1, TCRIT2, and TCRIT3 active low outputs are triggered when any unmasked channel exceeds its corresponding programmable limit and can be used to shutdown the system, to turn on the system fans or as a microcontroller interrupt function. The current status of the TCRIT1, TCRIT2, and TCRIT3 pins can be read back from the status registers through the SMBus interface. Two of the remote channels have two separate limits each that control the TCRIT1 and TCRIT2 pins. The remaining two channels and the local channel each have one limit to control both the TCRIT1 and TCRIT2 pins. The TCRIT3 pin shares the limits of the TCRIT2 pin but allows for different masking options. All limits have a shared programmable hysteresis register.
Diode fault detection circuitry in the LM95214 can detect the absence or fault state of a remote diode: whether D+ is shorted to VDD, D– or ground, or whether D+ is floating.
Remote Diode 1 and 2 temperature channels have programmable digital filters while the other two remote temperature channels utilize a fault-queue to avoid false triggering the TCRIT pins.
The LM95214 has a three-level address pin to connect up to 3 devices to the same SMBus master. LM95214 also has programmable conversion rate register as well as a shutdown mode for power savings. One round of conversions can be triggered in shutdown mode by writing to the one-shot register through the SMBus interface. LM95214 can be programmed to turn off unused channels for more power savings.
The LM95214 register set has an 8-bit data structure and includes:
The LM95214 takes approximately 190 ms to convert the Local Temperature, Remote Temperatures 1 through 4, and to update all of its registers. These conversions for each thermal diode are addressed in a round robin sequence. Only during the conversion process the busy bit (D7) in Status register (02h) is high. The conversion rate may be modified by the Conversion Rate bits found in the Configuration Register (03h). When the conversion rate is modified a delay is inserted between each round of conversions, the actual time for each round remains at 190 ms (typical all channels enabled). The time a round takes depends on the number of channels that are on. Different conversion rates will cause the LM95214 to draw different amounts of average supply current as shown in Figure 10. This curve assumes all the channels are on. If channels are turned off the average current will drop because the round robin time will decrease and the shutdown time will increase during each conversion interval.
The LM95214 always powers up to these known default states. The LM95214 remains in these states until after the first conversion.
OUTPUT PIN | TEMPERATURE CHANNEL LIMIT | ||||
---|---|---|---|---|---|
REMOTE 4 (°C) |
REMOTE 3 (°C) |
REMOTE 2 (°C) |
REMOTE 1 (°C) |
LOCAL (°C) |
|
TCRIT1 | Masked, 85 |
Masked, 85 |
110 | 110 | Masked, 85 |
TCRIT2 | 85 | 85 | 85 | 85 | 85 |
TCRIT3 | 85 | 85 | Masked, 85 |
Masked, 85 |
Masked, 85 |
The LM95214 operates as a slave on the SMBus, so the SMBCLK line is an input and the SMBDAT line is bidirectional. The LM95214 never drives the SMBCLK line and it does not support clock stretching. According to SMBus specifications, the LM95214 has a 7-bit slave address. Three SMBus device address can be selected by connecting A0 (pin 6) to either Low, Mid-Supply, or High voltages. The LM95214 has the following SMBus slave address:
A0 PIN STATE | SMBus DEVICE ADDRESS A[6:0] | |
---|---|---|
HEX | BINARY | |
Low | 18h | 001 1000 |
Mid-Supply | 4Dh | 100 1101 |
High | 4Eh | 100 1110 |
Each of the 5 temperature channels of LM95214 can be turned OFF independent from each other through the Channel Enable Register. Turning off unused channels will increase the conversion speed in the fastest conversion speed mode. If the slower conversion speed settings are used, disabling unused channels will reduce the average power consumption of LM95214.
To suppress erroneous remote temperature readings due to noise as well as increase the resolution of the temperature, the LM95214 incorporates a digital filter for Remote 1 and 2 Temperature Channels. When a filter is enabled the filtered readings are used for the TCRIT comparisons. There are two possible digital filter settings that are enabled through the Filter Setting Register at register address 0Fh. The filter for each channel can be set according to the following table:
R1F[1:0] OR R2F[1:0] | FILTER SETTING | |
---|---|---|
0 | 0 | No Filter |
0 | 1 | Filter (equivalent to Level 2 filter of the LM86/LM89) |
1 | 0 | Reserved |
1 | 1 | Enhanced Filter (Filter with transient noise clipping) |
Figure 11, Figure 12, and Figure 13 describe the filter output in response to a step input and an impulse input.
Figure 14 shows the filter in use in a typical system. Note that the two curves have been purposely offset for clarity. Inserting the filter does not induce an offset as shown.
To suppress erroneous TCRIT1,TCRIT2 and TCRIT3 triggering the LM95214 incorporates a Fault Queue for the unfiltered remote channels 3 and 4. The Fault Queue acts to ensure the remote temperature measurement of these channels is genuinely beyond the corresponding Tcrit limit by not triggering until three consecutive out of limit measurements have been made, see Figure 15 for an example. The Fault Queue defaults on upon power-up. The fault queue for channels 3 and 4 can be turned ON or OFF through bits 0 and 1 of the Configuration Register. When the fault queue is enabled, the TCRIT1, TCRIT2 and TCRIT3 pins will be triggered if the temperature is above the Tcrit limit for 3 consecutive conversions and the corresponding mask bit is 0 in the TCRIT Mask registers. Similarly the temperature needs to be below the Tcrit limit minus the hysteresis value for three consecutive conversions for the TCRIT1, TCRIT2 and TCRIT3 pins to deactivate.
Temperature data can only be read from the Local and Remote Temperature value registers. The data format for all temperature values is left justified 16-bit word available in two 8-bit registers. Unused bits will always report 0. All temperature data is clamped and will not roll over when a temperature exceeds full-scale value.
Remote temperature data for all channels can be represented by an 11-bit, two's complement word or unsigned binary word with an LSb (Least Significant Bit) equal to 0.125°C.
TEMPERATURE | DIGITAL OUTPUT | |
---|---|---|
BINARY | HEX | |
+125°C | 0111 1101 0000 0000 | 7D00h |
+25°C | 0001 1001 0000 0000 | 1900h |
+1°C | 0000 0001 0000 0000 | 0100h |
+0.125°C | 0000 0000 0010 0000 | 0020h |
0°C | 0000 0000 0000 0000 | 0000h |
−0.125°C | 1111 1111 1110 0000 | FFE0h |
−1°C | 1111 1111 0000 0000 | FF00h |
−25°C | 1110 0111 0000 0000 | E700h |
−55°C | 1100 1001 0000 0000 | C900h |
TEMPERATURE | DIGITAL OUTPUT | |
---|---|---|
BINARY | HEX | |
+255.875°C | 1111 1111 1110 0000 | FFE0h |
+255°C | 1111 1111 0000 0000 | FF00h |
+201°C | 1100 1001 0000 0000 | C900h |
+125°C | 0111 1101 0000 0000 | 7D00h |
+25°C | 0001 1001 0000 0000 | 1900h |
+1°C | 0000 0001 0000 0000 | 0100h |
+0.125°C | 0000 0000 0010 0000 | 0020h |
0°C | 0000 0000 0000 0000 | 0000h |
When the digital filter is enabled on Remote 1 and 2 channels temperature data is represented by a 13-bit unsigned binary or 12-bit plus sign (two's complement) word with an LSb equal to 0.03125°C.
TEMPERATURE | DIGITAL OUTPUT | |
---|---|---|
BINARY | HEX | |
+125°C | 0111 1101 0000 0000 | 7D00h |
+25°C | 0001 1001 0000 0000 | 1900h |
+1°C | 0000 0001 0000 0000 | 0100h |
+0.03125°C | 0000 0000 0000 1000 | 0008h |
0°C | 0000 0000 0000 0000 | 0000h |
−0.03125°C | 1111 1111 1111 1000 | FFF8h |
−1°C | 1111 1111 0000 0000 | FF00h |
−25°C | 1110 0111 0000 0000 | E700h |
−55°C | 1100 1001 0000 0000 | C900h |
TEMPERATURE | DIGITAL OUTPUT | |
---|---|---|
BINARY | HEX | |
+255.875°C | 1111 1111 1110 0000 | FFE0h |
+255°C | 1111 1111 0000 0000 | FF00h |
+201°C | 1100 1001 0000 0000 | C900h |
+125°C | 0111 1101 0000 0000 | 7D00h |
+25°C | 0001 1001 0000 0000 | 1900h |
+1°C | 0000 0001 0000 0000 | 0100h |
+0.03125°C | 0000 0000 0000 1000 | 0008h |
0°C | 0000 0000 0000 0000 | 0000h |
Local Temperature data is only represented by an 11-bit, two's complement, word with an LSb equal to 0.125°C.
TEMPERATURE | DIGITAL OUTPUT | |
---|---|---|
BINARY | HEX | |
+125°C | 0111 1101 0000 0000 | 7D00h |
+25°C | 0001 1001 0000 0000 | 1900h |
+1°C | 0000 0001 0000 0000 | 0100h |
+0.125°C | 0000 0000 0010 0000 | 0020h |
0°C | 0000 0000 0000 0000 | 0000h |
−0.125°C | 1111 1111 1110 0000 | FFE0h |
−1°C | 1111 1111 0000 0000 | FF00h |
−25°C | 1110 0111 0000 0000 | E700h |
−55°C | 1100 1001 0000 0000 | C900h |
The SMBDAT output is an open-drain output and does not have internal pullups. A high level will not be observed on this pin until pullup current is provided by some external source, typically a pullup resistor. Choice of resistor value depends on many system factors but, in general, the pullup resistor must be as large as possible without effecting the SMBus desired data rate. This will minimize any internal temperature reading errors due to internal heating of the LM95214. The maximum resistance of the pullup to provide a 2.1-V high level, based on LM95214 specification for High Level Output Current with the supply voltage at 3 V, is 82 kΩ (5%) or 88.7 kΩ (1%).
The LM95214's TCRIT pins are active-low open-drain outputs and do not include internal pullup resistors. A high level will not be observed on these pins until pullup current is provided by some external source, typically a pullup resistor. Choice of resistor value depends on many system factors but, in general, the pullup resistor must be as large as possible without effecting the performance of the device receiving the signal. This will minimize any internal temperature reading errors due to internal heating of the LM95214. The maximum resistance of the pullup to provide a 2.1-V high level, based on LM95214 specification for High Level Output Current with the supply voltage at 3 V, is 82 kΩ (5%) or 88.7 kΩ (1%). The three TCRIT pins can each sink 6 mA of current and still ensured a Logic Low output voltage of 0.4 V. If all three pins are set at maximum current this will cause a power dissipation of 7.2 mW. This power dissipation combined with a thermal resistance of 77.8°C/W will cause the LM95214's junction temperature to rise approximately 0.6°C and thus cause the Local temperature reading to shift. This can only be cancelled out if the environment that the LM95214 is enclosed in has stable and controlled air flow over the LM95214, as airflow can cause the thermal resistance to change dramatically.
Figure 16 describes a simplified diagram of the temperature comparison and status register logic. Figure 17, Figure 18, and Figure 19 describe simplified logic diagrams of the circuitry associated with the status registers, mask registers, and the TCRIT output pins.
If enabled, local temperature is compared to the user programmable Local Tcrit Limit Register (Default Value = 85°C). The result of this comparison is stored in Status Register 2, Status Register 3 and Status Register 4 (see Figure 16). The comparison result can trigger TCRIT1 pin, TCRIT2 pin or TCRIT3 pin depending on the settings in the TCRIT1 Mask, TCRIT2 Mask and TCRIT3 Mask Registers (see Figure 17, Figure 18, and Figure 19). The comparison result can also be read back from the Status Register 2, Status Register 3 and Status Register 4.
If enabled, remote temperature 1 is compared to the user programmable Remote 1 Tcrit-1 Limit Register (Default Value 110°C) and Remote 1 Tcrit-2 Limit Register (Default Value = 85°C). The result of this comparison is stored in Status Register 2, Status Register 3 and Status Register 4 (see Figure 16). The comparison result can trigger TCRIT1 pin, TCRIT2 pin or TCRIT3 pin depending on the settings in the TCRIT1 Mask, TCRIT2 Mask and TCRIT3 Mask Registers (see Figure 17, Figure 18, and Figure 19). The comparison result can also be read back from the Status Register 2, Status Register 3 and Status Register 4. The remote temperature 2 operates in a similar manner to remote temperature 1 using its associated user programmable limit registers: Remote 2 Tcrit-1 Limit Register (Default Value 110°C) and Remote 2 Tcrit-2 Limit Register (Default Value = 85°C). When enabled, the remote temperature 3 is compared to the user programmable Remote 3 Tcrit Limit Register (Default Value 85°C). The comparison result can trigger TCRIT1 pin, TCRIT2 pin or TCRIT3 pin depending on the settings in the TCRIT1 Mask, TCRIT2 Mask and TCRIT3 Mask Registers. The comparison result can also be read back from the Status Register 2, Status Register 3 and Status Register 4. The remote temperature 4 operates in a similar manner to remote temperature 3 using its associated user programmable limit register: Remote 4 Tcrit Limit Register (Default Value 85°C).
TCRIT1 | TCRIT2 | TCRIT3 | |
---|---|---|---|
Remote 4 | Remote 4 Tcrit Limit |
Remote 4 Tcrit Limit |
Remote 4 Tcrit Limit |
Remote 3 | Remote 3 Tcrit Limit |
Remote 3 Tcrit Limit |
Remote 3 Tcrit Limit |
Remote 2 | Remote 2 Tcrit-1 Limit |
Remote 2 Tcrit-2 Limit |
Remote 2 Tcrit-2 Limit |
Remote 1 | Remote 1 Tcrit-1 Limit |
Remote 1 Tcrit-2 Limit |
Remote 1 Tcrit-2 Limit |
Local | Local Tcrit Limit |
Local Tcrit Limit |
Local Tcrit Limit |
The TCRIT response diagram of Figure 20 shows the local temperature interaction with the Tcrit limit and hysteresis value. As can be seen in the diagram when the local temperature exceeds the Tcrit limit register value the LTn Status bit is set and the T_CRITn output(s) is/are activated. The Status bit(s) and outputs are not deactivated until the temperature goes below the value calculated by subtracting the Common Hysteresis value programmed from the limit. This diagram mainly shows an example function of the hysteresis and is not meant to show complete function of the possible settings and options of all the TCRIT outputs and limit values.
The LM95214 is equipped with operational circuitry designed to detect fault conditions concerning the remote diodes. In the event that the D+ pin is detected as shorted to GND, D−, VDD or D+ is floating, the Remote Temperature reading is –128.000°C if signed format is selected and 0°C if unsigned format is selected. In addition, the appropriate status register bits RD1M or RD2M (D1 or D0) are set.
The data registers in the LM95214 are selected by the Command Register. At power-up the Command Register is set to 00, the location for the Read Local Temperature Register. The Command Register latches the last location it was set to. Each data register in the LM95214 falls into one of three types of user accessibility:
A Write to the LM95214 will always include the address byte and the command byte. A write to any register requires one data byte.
Reading the LM95214 can take place either of two ways:
The data byte has the most significant bit first. At the end of a read, the LM95214 can accept either acknowledge or No Acknowledge from the Master (No Acknowledge is typically used as a signal for the slave that the Master has read its last byte). It takes the LM95214 190 ms (typical, all channels enabled) to measure the temperature of the remote diodes and internal diode. When retrieving all 11 bits from a previous remote diode temperature measurement, the master must insure that all 11 bits are from the same temperature conversion. This may be achieved by reading the MSB register first. The LSB will be locked after the MSB is read. The LSB will be unlocked after being read. If the user reads MSBs consecutively, each time the MSB is read, the LSB associated with that temperature will be locked in and override the previous LSB value locked-in.
In the event that the SMBus Master is RESET while the LM95214 is transmitting on the SMBDAT line, the LM95214 must be returned to a known state in the communication protocol. This may be done in one of two ways:
The One-Shot register is used to initiate a round of conversions and comparisons when the device is in standby mode, after which the device returns to standby. This is not a data register and it is the write operation that causes the one-shot conversion. The data written to this address is irrelevant and is not stored. A zero will always be read from this register. All the channels that are enabled in the Channel Enable Register will be converted once and the TCRIT1, TCRIT2, and TCRIT3 pins will reflect the comparison results based on this round of conversion results of the channels that are not masked.
Command register selects which registers will be read from or written to. Data for this register must be transmitted during the Command Byte of the SMBus write communication.
P7 | P6 | P5 | P4 | P3 | P2 | P1 | P0 |
---|---|---|---|---|---|---|---|
Command Byte |
P0-P7: Command
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Local Temp MSB | 0x10 | RO | SIGN | 64 | 32 | 16 | 8 | 4 | 2 | 1 | – |
Local Temp LSB | 0x20 | RO | 1/2 | 1/4 | 1/8 | 0 | 0 | 0 | 0 | 0 | – |
Remote Temp 1 MSB – Signed | 0x11 | RO | SIGN | 64 | 32 | 16 | 8 | 4 | 2 | 1 | – |
Remote Temp 1 LSB – Signed, Digital Filter Off | 0x21 | RO | 1/2 | 1/4 | 1/8 | 0 | 0 | 0 | 0 | 0 | – |
Remote Temp 1 LSB – Signed, Digital Filter On | 1/16 | 1/32 | |||||||||
Remote Temp 2 MSB – Signed | 0x12 | RO | SIGN | 64 | 32 | 16 | 8 | 4 | 2 | 1 | – |
Remote Temp 2 LSB – Signed, Digital Filter Off | 0x22 | RO | 1/2 | 1/4 | 1/8 | 0 | 0 | 0 | 0 | 0 | – |
Remote Temp 2 LSB – Signed, Digital Filter On | 1/16 | 1/32 | |||||||||
Remote Temp 3 MSB – Signed | 0x13 | RO | SIGN | 64 | 32 | 16 | 8 | 4 | 2 | 1 | – |
Remote Temp 3 LSB – Signed | 0x23 | RO | 1/2 | 1/4 | 1/8 | 0 | 0 | 0 | 0 | 0 | – |
Remote Temp 4 MSB – Signed | 0x14 | RO | SIGN | 64 | 32 | 16 | 8 | 4 | 2 | 0 | – |
Remote Temp 4 LSB – Signed | 0x24 | RO | 1/2 | 1/4 | 1/8 | 0 | 0 | 0 | 0 | 0 | – |
Remote Temp 1 MSB – Unsigned | 0x19 | RO | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | – |
Remote Temp 1 LSB – Unsigned, Digital Filter Off | 0x29 | RO | 1/2 | 1/4 | 1/8 | 0 | 0 | 0 | 0 | 0 | – |
Remote Temp 1 LSB – Unsigned, Digital Filter On | 1/16 | 1/32 | |||||||||
Remote Temp 2 MSB – Unsigned | 0x1A | RO | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | – |
Remote Temp 2 LSB – Unsigned, Digital Filter Off | 0x2A | RO | 1/2 | 1/4 | 1/8 | 0 | 0 | 0 | 0 | 0 | – |
Remote Temp 2 LSB – Unsigned, Digital Filter On | 1/16 | 1/32 | |||||||||
Remote Temp 3 MSB – Unsigned | 0x1B | RO | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | – |
Remote Temp 3 LSB – Unsigned | 0x2B | RO | 1/2 | 1/4 | 1/8 | 0 | 0 | 0 | 0 | 0 | – |
Remote Temp 4 MSB – Unsigned | 0x1C | RO | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | – |
Remote Temp 4 LSB – Unsigned | 0x2C | RO | 1/2 | 1/4 | 1/8 | 0 | 0 | 0 | 0 | 0 | – |
Remote 1 Offset | 0x31 | R/W | SIGN | 32 | 16 | 8 | 4 | 2 | 1 | 1/2 | 0x00 |
Remote 2 Offset | 0x32 | R/W | SIGN | 32 | 16 | 8 | 4 | 2 | 1 | 1/2 | 0x00 |
Remote 3 Offset | 0x33 | R/W | SIGN | 32 | 16 | 8 | 4 | 2 | 1 | 1/2 | 0x00 |
Remote 4 Offset | 0x34 | R/W | SIGN | 32 | 16 | 8 | 4 | 2 | 1 | 1/2 | 0x00 |
Configuration | 0x03 | R/W | – | STBY | – | – | – | – | R4QE | R3QE | 0x03 |
Conversion Rate | 0x04 | R/W | – | – | – | – | – | – | CR1 | CR0 | 0x02 |
Channel Conversion Enable | 0x05 | R/W | – | – | – | R4CE | R3CE | R2CE | R1CE | LCE | 0x1F |
Filter Setting | 0x06 | R/W | – | – | – | – | R2F1 | R2F0 | R1F1 | R1F0 | 0x0F |
1-shot | 0x0F | WO | – | – | – | – | – | – | – | – | – |
Common Status Register | 0x02 | RO | BUSY | NR | – | – | SR4F | SR3F | SR2F | SR1F | 0x00 |
Status 1 (Diode Fault) | 0x07 | RO | R4DO | R4DS | R3DO | R3DS | R2DO | R2DS | R1DO | R1DS | – |
Status 2 (TCRIT1) | 0x08 | RO | – | – | – | R4T1 | R3T1 | R2T1 | R1T1 | LT1 | – |
Status 3 (TCRIT2) | 0x09 | RO | – | – | – | R4T2 | R3T2 | R2T2 | R1T2 | LT2 | – |
Status 4 (TCRIT3) | 0x0A | RO | – | – | – | R4T3 | R3T3 | R2T3 | R1T3 | LT3 | – |
TCRIT1 Mask | 0x0C | R/W | – | – | – | R4TM | R3TM | R2T1M | R1T1M | LTM | 0x19 |
TCRIT2 Mask | 0x0D | R/W | – | – | – | R4TM | R3TM | R2T2M | R1T2M | LTM | 0x00 |
TCRIT3 Mask | 0x0E | R/W | – | – | – | R4TM | R3TM | R2T2M | R1T2M | LTM | 0x07 |
Local Tcrit Limit | 0x40 | R/W | 0 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | 0x55 |
Remote 1 Tcrit-1 Limit | 0x41 | R/W | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | 0x6E |
Remote 2 Tcrit-1 Limit | 0x42 | R/W | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | 0x6E |
Remote 3 Tcrit Limit | 0x43 | R/W | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | 0x55 |
Remote 4 Tcrit Limit | 0x44 | R/W | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | 0x55 |
Remote 1 Tcrit-2 and Tcrit-3 Limit | 0x49 | R/W | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | 0x55 |
Remote 2 Tcrit-2 and Tcrit-3 Limit | 0x4A | R/W | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | 0x55 |
Common Tcrit Hysteresis | 0x5A | R/W | 0 | 0 | 0 | 16 | 8 | 4 | 2 | 1 | 0x0A |
Manufacturer ID | 0xFE | RO | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0x01 |
Revision ID | 0xFF | RO | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 0x79 |
For data synchronization purposes, the MSB register must be read first if the user wants to read both MSB and LSB registers. The LSB will be locked after the MSB is read. The LSB will be unlocked after being read. If the user reads MSBs consecutively, each time the MSB is read, the LSB associated with that temperature will be locked in and override the previous LSB value locked-in
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Local Temp MSB | 0x10 | RO | SIGN | 64 | 32 | 16 | 8 | 4 | 2 | 1 | – |
Local Temp LSB | 0x20 | RO | 1/2 | 1/4 | 1/8 | 0 | 0 | 0 | 0 | 0 | – |
Bit(s) | Bit Name | Read/Write | Description | |
---|---|---|---|---|
7 | SIGN | RO | Sign bit | The Local temperature MSB value register range is +127°C to −128°C. The value programmed in this register is used to determine a local temperature error event. |
6 | 64 | RO | bit weight 64°C | |
5 | 32 | RO | bit weight 32°C | |
4 | 16 | RO | bit weight 16°C | |
3 | 8 | RO | bit weight 8°C | |
2 | 4 | RO | bit weight 4°C | |
1 | 2 | RO | bit weight 2°C | |
0 | 1 | RO | bit weight 1°C |
Bit(s) | Bit Name | Read/Write | Description | |
---|---|---|---|---|
7 | 1/2 | RO | bit weight 1/2°C (0.5°C) | The Local Limit register range is 0°C to 127°C. The value programmed in this register is used to determine a local temperature error event. |
6 | 1/4 | RO | bit weight 1/4°C (0.25°C) | |
5 | 1/8 | RO | bit weight 1/8°C (0.125°C) | |
4-0 | 0 | RO | Reserved – will report 0 when read. |
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Remote Temp 1 MSB – Signed | 0x11 | RO | SIGN | 64 | 32 | 16 | 8 | 4 | 2 | 1 | – |
Remote Temp 1 LSB – Signed, Digital Filter Off | 0x21 | RO | 1/2 | 1/8 | 0 | 0 | 0 | 0 | 0 | 0 | – |
Remote Temp 1 LSB – Signed, Digital Filter On | 1/16 | 1/32 | |||||||||
Remote Temp 2 MSB – Signed | 0x12 | RO | SIGN | 64 | 32 | 16 | 8 | 4 | 2 | 1 | – |
Remote Temp 2 LSB – Signed, Digital Filter Off | 0x22 | RO | 1/2 | 1/8 | 0 | 0 | 0 | 0 | 0 | 0 | – |
Remote Temp 2 LSB – Signed, Digital Filter On | 1/16 | 1/32 | |||||||||
Remote Temp 3 MSB – Signed | 0x13 | RO | SIGN | 64 | 32 | 16 | 8 | 4 | 2 | 1 | – |
Remote Temp 3 LSB – Signed | 0x23 | RO | 1/2 | 1/8 | 0 | 0 | 0 | 0 | 0 | 0 | – |
Remote Temp 4 MSB – Signed | 0x14 | RO | SIGN | 64 | 32 | 16 | 8 | 4 | 2 | 0 | – |
Remote Temp 4 LSB – Signed | 0x24 | RO | 1/2 | 1/8 | 0 | 0 | 0 | 0 | 0 | 0 | – |
The Local temperature MSB value register range is +127°C to −128°C. The value programmed in this register is used to determine a local temperature error event.
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7 | SIGN | RO | Sign bit |
6 | 64 | RO | bit weight 64°C |
5 | 32 | RO | bit weight 32°C |
4 | 16 | RO | bit weight 16°C |
3 | 8 | RO | bit weight 8°C |
2 | 4 | RO | bit weight 4°C |
1 | 2 | RO | bit weight 2°C |
0 | 1 | RO | bit weight 1°C |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7 | 1/2 | RO | bit weight 1/2°C (0.5°C) |
6 | 1/4 | RO | bit weight 1/4°C (0.25°C) |
5 | 1/8 | RO | bit weight 1/8°C (0.125°C) |
4 | 0 or 1/16 | RO | When the digital filter is disabled this bit will always read 0. When the digital filter is enabled this bit will report 1/16°C (0.0625°C) bit state. |
3 | 0 or 1/32 | RO | When the digital filter is disabled this bit will always read 0. When the digital filter is enabled this bit will report 1/32°C (0.03125°C) bit state. |
2-0 | 0 | RO | Reserved – will report 0 when read. |
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Remote Temp 1 MSB – Unsigned | 0x19 | RO | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | – |
Remote Temp 1 LSB – Unsigned, Digital Filter Off | 0x29 | RO | 1/2 | 1/8 | 0 | 0 | 0 | 0 | 0 | 0 | – |
Remote Temp 1 LSB – Unsigned, Digital Filter On | 1/16 | 1/32 | |||||||||
Remote Temp 2 MSB – Unsigned | 0x1A | RO | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | – |
Remote Temp 2 LSB – Unsigned, Digital Filter Off | 0x2A | RO | 1/2 | 1/8 | 0 | 0 | 0 | 0 | 0 | 0 | – |
Remote Temp 2 LSB – Unsigned, Digital Filter On | 1/16 | 1/32 | |||||||||
Remote Temp 3 MSB – Unsigned | 0x1B | RO | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | – |
Remote Temp 3 LSB – Unsigned | 0x2B | RO | 1/2 | 1/8 | 0 | 0 | 0 | 0 | 0 | 0 | – |
Remote Temp 4 MSB – Unsigned | 0x1C | RO | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | – |
Remote Temp 4 LSB – Unsigned | 0x2C | RO | 1/2 | 1/8 | 0 | 0 | 0 | 0 | 0 | 0 | – |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7 | SIGN | RO | bit weight 128°C |
6 | 64 | RO | bit weight 64°C |
5 | 32 | RO | bit weight 32°C |
4 | 16 | RO | bit weight 16°C |
3 | 8 | RO | bit weight 8°C |
2 | 4 | RO | bit weight 4°C |
1 | 2 | RO | bit weight 2°C |
0 | 1 | RO | bit weight 1°C |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7 | 1/2 | RO | bit weight 1/2°C (0.5°C) |
6 | 1/4 | RO | bit weight 1/4°C (0.25°C) |
5 | 1/8 | RO | bit weight 1/8°C (0.125°C) |
4 | 0 or 1/16 | RO | When the digital filter is disabled this bit will always read 0. When the digital filter is enabled this bit will report 1/16°C (0.0625°C) bit state. |
3 | 0 or 1/32 | RO | When the digital filter is disabled this bit will always read 0. When the digital filter is enabled this bit will report 1/32°C (0.03125°C) bit state. |
2-0 | 0 | RO | Reserved – will report 0 when read. |
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Remote 1 Offset | 0x31 | R/W | SIGN | 32 | 16 | 8 | 4 | 2 | 1 | 1/2 | 0x00 |
Remote 2 Offset | 0x32 | R/W | SIGN | 32 | 16 | 8 | 4 | 2 | 1 | 1/2 | 0x00 |
Remote 3 Offset | 0x33 | R/W | SIGN | 32 | 16 | 8 | 4 | 2 | 1 | 1/2 | 0x00 |
Remote 4 Offset | 0x34 | R/W | SIGN | 32 | 16 | 8 | 4 | 2 | 1 | 1/2 | 0x00 |
Bit(s) | Bit Name | Read/Write | Description | |
---|---|---|---|---|
7 | SIGN | R/W | Sign bit | All registers have 2’s complement format. The offset range for each remote is +63.5°C/−64°C. The value programmed in this register is directly added to the actual reading of the ADC and the modified number is reported in the remote value registers. |
6 | 32 | R/W | bit weight 32°C | |
5 | 16 | R/W | bit weight 16°C | |
4 | 8 | R/W | bit weight 8°C | |
3 | 4 | R/W | bit weight 4°C | |
2 | 2 | R/W | bit weight 2°C | |
1 | 1 | R/W | bit weight 1°C | |
0 | 1/2 | R/W | bit weight 1/2°C (0.5°C) |
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Configuration | 0×03 | R/W | – | STBY | – | – | – | – | R4QE | R3QE | 0×03 |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7 | – | RO | Reserved will report 0 when read. |
6 | STBY | R/W | Software Standby 1 – standby (when in this mode one conversion sequence can be initiated by writing to the one-shot register) 0 – active/converting |
5–2 | – | RO | Reserved – will report 0 when read. |
1 | R4QE | R/W | Fault queue enable for Remote 4 1– Fault queue enabled 0– Fault queue disabled |
0 | R3QE | R/W | Fault queue enable for Remote 3 1– Fault queue enabled 0– Fault queue disabled |
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Conversion Rate | 0×04 | R/W | – | – | – | – | – | – | CR1 | CR0 | 0×02 |
Bit(s) | Bit Name | Read/Write | Description | |
---|---|---|---|---|
7-2 | – | RO | Reserved – will report 0 when read. | |
1-0 | CR[1:0] | R/W | Conversion rate control bits modify the time interval for conversion of the channels enabled. The channels enabled are converted sequentially then standby mode enabled for the remainder of the time interval. | |
CR[1:0] | Conversion Rate | |||
00 | continuous (30 ms to 143 ms) | |||
01 | 0.364 s | |||
10 | 1s | |||
11 | 2.5 s |
When a conversion is disabled for a particular channel it is skipped. The continuous conversion rate is effected all other conversion rates are not effected as extra standby time is inserted to compensate. See Conversion Rate Register description.
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Channel Conversion Enable | 0×05 | R/W | – | – | – | R4CE | R3CE | R2CE | R1CE | LCE | 0×1F |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7–5 | – | RO | Reserved – will report 0 when read. |
4 | R4CE | R/W | Remote 4 Temperature Conversion Enable 1– Remote 4 temp conversion enabled 0– Remote 4 temp conversion disabled |
3 | R3CE | R/W | Remote 3 Temperature Conversion Enable 1– Remote 3 temp conversion enabled 0– Remote 3 temp conversion disabled |
2 | R2CE | R/W | Remote 2 Temperature Conversion Enable 1– Remote 2 temp conversion enabled 0– Remote 2 temp conversion disabled |
1 | R1CE | R/W | Remote 1 Temperature Conversion Enable 1– Remote 1 temp conversion enabled 0– Remote 1 temp conversion disabled |
0 | LCE | R/W | Local Temperature Conversion Enable 1– Local temp conversion enabled 0– Local temp conversion disabled |
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Filter Setting | 0x06 | R/W | – | – | – | – | R2F1 | R2F0 | R1F1 | R1F0 | 0x0F |
Bit(s) | Bit Name | Read/Write | Description | |
---|---|---|---|---|
7–4 | – | RO | Reserved – will report 0 when read. | |
3–2 | R2F[1:0] | R/W | Remote Channel 2 Filter Enable Bits | |
R2F[1:0] | Digital Filter State | |||
00 | disable all digital filtering | |||
01 | enable basic filter | |||
10 | reserved (do not use) | |||
11 | enable enhanced filter | |||
1–0 | R1F[1:0] | R/W | Remote Channel 1 Filter Enable | |
R1F[1:0] | Filter State | |||
00 | disable all digital filtering | |||
01 | enable basic filter | |||
10 | reserved (do not use) | |||
11 | enable enhanced filter |
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
1-Shot | 0×0F | WO | – | – | – | – | – | – | – | – | – |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7–0 | - | WO | Writing to this register activates one conversion for all the enabled channels if the chip is in standby mode (that is,. standby bit = 1). The actual data written does not matter and is not stored. |
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Common Status Register | 0×02 | RO | BUSY | NR | – | – | SR4F | SR3F | SR2F | SR1F | 0×00 |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7 | BUSY | RO | Busy bit (device converting) |
6 | NR | RO | Not Ready bit (30 ms), indicates power up initialization sequence is in progress |
5–4 | – | RO | Reserved – will report 0 when read. |
3 | SR4F | RO | Status Register 4 Flag: 1 – indicates that Status Register 4 has at least one bit set 0 – indicates that all of Status Register 4 bits are cleared |
2 | SR3F | RO | Status Register 3 Flag: 1 – indicates that Status Register 3 has at least one bit set 0 – indicates that all of Status Register 3 bits are cleared |
1 | SR2F | RO | Status Register 2 Flag: 1 – indicates that Status Register 2 has at least one bit set 0 – indicates that all of Status Register 2 bits are cleared |
0 | SR1F | RO | Status Register 1 Flag: 1 – indicates that Status Register 1 has at least one bit set 0 – indicates that all of Status Register 1 bits are cleared |
Status fault bits for open or shorted diode (that is,. Short Fault: D+ shorted to Ground or D-; Open Fault: D+ shorted to VDD, or floating). During fault conditions the temperature reading is 0 °C if unsigned value registers are read or –128.000 °C if signed value registers are read.
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Status 1 (Diode Fault) | 0×07 | RO | R4DO | R4DS | R3DO | R3DS | R2DO | R2DS | R1DO | R1DS | – |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7 | R4DO | RO | Remote 4 diode open fault status: 1 – indicates that remote 4 diode has an "open" fault 0 – indicates that remote 4 diode does not have an "open" fault |
6 | R4DS | RO | Remote 4 diode short fault status: 1 – indicates that remote 4 diode has a "short" fault 0 – indicates that remote 4 diode does not have a "short" fault |
5 | R3DO | RO | Remote 3 diode open fault status: 1 – indicates that remote 3 diode has an "open" fault 0 – indicates that remote 3 diode does not have an "open" fault |
4 | R3DS | RO | Remote 3 diode short fault status: 1 – indicates that remote 3 diode has a "short" fault 0 – indicates that remote 3 diode does not have a "short" fault |
3 | R2DO | RO | Remote 2 diode open fault status: 1 – indicates that remote 2 diode has an "open" fault 0 – indicates that remote 2 diode does not have an "open" fault |
2 | R2DS | RO | Remote 2 diode short fault status: 1 – indicates that remote 2 diode has a "short" fault 0 – indicates that remote 2 diode does not have a "short" fault |
1 | R1DO | RO | Remote 1 diode open fault status: 1 – indicates that remote 1 diode has an "open" fault 0 – indicates that remote 1 diode does not have an "open" fault |
0 | R1DS | RO | Remote 1 diode short fault status: 1 – indicates that remote 1 diode has a "short" fault 0 – indicates that remote 1 diode does not have a "short" fault |
Status bits for TCRIT1. When one or more of these bits are set and if not masked the TCRIT1 output will activate. TCRIT1 will deactivate when all these bits are cleared.
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Status 2 (TCRIT1) | 0×08 | RO | – | – | – | R4T1 | R3T1 | R2T1 | R1T1 | LT1 | – |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7–5 | - | RO | Reserved – will report 0 when read. |
4 | R4T1 | RO | Remote 4 Tcrit Status: 1 – indicates that remote 4 reading is greater than or equal to the value set in Remote 4 Tcrit Limit register 0 – indicates that that remote 4 reading is less than the value set in Remote 4 Tcrit Limit register minus the Common Hysteresis value |
3 | R3T1 | RO | Remote 3 Tcrit Status: 1 – indicates that remote 3 reading is greater than or equal to the value set in Remote 3 Tcrit Limit register 0 – indicates that that remote 3 reading is less than the value set in Remote 3 Tcrit Limit register minus the Common Hysteresis value |
2 | R2T1 | RO | Remote 2 Tcrit-1 Status: 1 – indicates that remote 2 reading is greater than or equal to the value set in Remote 2 Tcrit-1 Limit register 0 – indicates that that remote 2 reading is less than the value set in Remote 2 Tcrit-1 Limit register minus the Common Hysteresis value |
1 | R1T1 | RO | Remote 1 Tcrit-1 Status: 1 – indicates that remote 1 reading is greater than or equal to the value set in Remote 1 Tcrit-1 Limit register 0 – indicates that that remote 1 reading is less than the value set in Remote 1 Tcrit-1 Limit register minus the Common Hysteresis value |
0 | LT1 | RO | Local Tcrit Status: 1 – indicates that local reading is greater than or equal to the value set in Local Tcrit Limit register 0 – indicates that local reading is less than the value set in Local Tcrit Limit register minus the Common Hysteresis value |
Status bits for TCRIT2. When one or more of these bits are set and if not masked the TCRIT2 output will activate. TCRIT2 will deactivate when all these bits are cleared.
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Status 3 (TCRIT2) | 0×09 | RO | – | – | – | R4T2 | R3T2 | R2T2 | R1T2 | LT2 | – |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7–5 | - | RO | Reserved – will report 0 when read. |
4 | R4T2 | RO | Remote 4 Tcrit Status: 1 – indicates that remote 4 reading is greater than or equal to the value set in Remote 4 Tcrit Limit register 0 – indicates that that remote 4 reading is less than the value set in Remote 4 Tcrit Limit register minus the Common Hysteresis value |
3 | R3T2 | RO | Remote 3 Tcrit Status: 1 – indicates that remote 3 reading is greater than or equal to the value set in Remote 3 Tcrit Limit register 0 – indicates that that remote 3 reading is less than the value set in Remote 3 Tcrit Limit register minus the Common Hysteresis value |
2 | R2T2 | RO | Remote 2 Tcrit-2 Status: 1 – indicates that remote 2 reading is greater than or equal to the value set in Remote 2 Tcrit-2 Limit register 0 – indicates that that remote 2 reading is less than the value set in Remote 2 Tcrit-2 Limit register minus the Common Hysteresis value |
1 | R1T2 | RO | Remote 1 Tcrit-2 Status: 1 – indicates that remote 1 reading is greater than or equal to the value set in Remote 1 Tcrit-2 Limit register 0 – indicates that that remote 1 reading is less than the value set in Remote 1 Tcrit-2 Limit register minus the Common Hysteresis value |
0 | LT2 | RO | Local Tcrit Status: 1 – indicates that local reading is greater than or equal to the value set in Local Tcrit Limit register 0 – indicates that local reading is less than the value set in Local Tcrit Limit register minus the Common Hysteresis value |
Status bits for TCRIT3. When one or more of these bits are set and if not masked the TCRIT3 output will activate. TCRIT3 will deactivate when all these bits are cleared.
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Status 4 (TCRIT3) | 0×0A | RO | – | – | – | R4T3 | R3T3 | R2T3 | R1T3 | LT3 | – |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7–5 | - | RO | Reserved – will report 0 when read. |
4 | R4T3 | RO | Remote 4 Tcrit Status: 1 – indicates that remote 4 reading is greater than or equal to the value set in Remote 4 Tcrit Limit register 0 – indicates that that remote 4 reading is less than the value set in Remote 4 Tcrit Limit register minus the Common Hysteresis value |
3 | R3T3 | RO | Remote 3 Tcrit Status: 1 – indicates that remote 3 reading is greater than or equal to the value set in Remote 3 Tcrit Limit register 0 – indicates that that remote 3 reading is less than the value set in Remote 3 Tcrit Limit register minus the Common Hysteresis value |
2 | R2T3 | RO | Remote 2 Tcrit-2 Status: 1 – indicates that remote 2 reading is greater than or equal to the value set in Remote 2 Tcrit-2 Limit register 0 – indicates that that remote 2 reading is less than the value set in Remote 2 Tcrit-2 Limit register minus the Common Hysteresis value |
1 | R1T3 | RO | Remote 1 Tcrit-2 Status: 1 – indicates that remote 1 reading is greater than or equal to the value set in Remote 1 Tcrit-2 Limit register 0 – indicates that that remote 1 reading is less than the value set in Remote 1 Tcrit-2 Limit register minus the Common Hysteresis value |
0 | LT3 | RO | Local Tcrit Status: 1 – indicates that local reading is greater than or equal to the value set in Local Tcrit Limit register 0 – indicates that local reading is less than the value set in Local Tcrit Limit register minus the Common Hysteresis value |
The mask bits in this register allow control over which error events propagate to the TCRIT1 pin.
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
TCRIT1 Mask | 0×0C | R/W | – | – | – | R4TM | R3TM | R2T1M | R1T1M | LTM | 0×19 |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7-5 | – | RO | Reserved – will report 0 when read. |
4 | R4TM | R/W | Remote 4 Tcrit Mask: 1 – prevents the remote 4 temperature error event from propagating to the TCRIT1 pin 0 – allows the remote 4 temperature error event to propagate to the TCRIT1 pin |
3 | R3TM | R/W | Remote 3 Tcrit Mask: 1 – prevents the remote 3 temperature error event from propagating to the TCRIT1 pin 0 – allows the remote 3 temperature error event to propagate to the TCRIT1 pin |
2 | R2T1M | R/W | Remote 2 Tcrit-1 Mask: 1 – prevents the remote 2 temperature error event from propagating to the TCRIT1 pin 0 – allows the remote 2 temperature error event to propagate to the TCRIT1 pin |
1 | R1T1M | R/W | Remote 1 Tcrit-1 Mask: 1 – prevents the remote 1 temperature error event from propagating to the TCRIT1 pin 0 – allows the remote 1 temperature error event to propagate to the TCRIT1 pin |
0 | LTM | R/W | Local Tcrit Mask: 1 – prevents the local temperature error event from propagating to the TCRIT1 pin 0 – allows the local temperature error event to propagate to the TCRIT1 pin |
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
TCRIT2 Mask | 0×0D | R/W | – | – | – | R4TM | R3TM | R2T2M | R1T2M | LTM | 0×00 |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7-5 | – | RO | Reserved – will report 0 when read. |
4 | R4TM | R/W | Remote 4 Tcrit Mask: 1 – prevents the remote 4 temperature error event from propagating to the TCRIT2 pin 0 – allows the remote 4 temperature error event to propagate to the TCRIT2 pin |
3 | R3TM | R/W | Remote 3 Tcrit Mask: 1 – prevents the remote 3 temperature error event from propagating to the TCRIT2 pin 0 – allows the remote 3 temperature error event to propagate to the TCRIT2 pin |
2 | R2T2M | R/W | Remote 2 Tcrit-2 Mask: 1 – prevents the remote 2 temperature error event from propagating to the TCRIT2 pin 0 – allows the remote 2 temperature error event to propagate to the TCRIT2 pin |
1 | R1T2M | R/W | Remote 1 Tcrit-2 Mask: 1 – prevents the remote 1 temperature error event from propagating to the TCRIT2 pin 0 – allows the remote 1 temperature error event to propagate to the TCRIT2 pin |
0 | LTM | R/W | Local Tcrit Mask: 1 – prevents the local temperature error event from propagating to the TCRIT2 pin 0 – allows the local temperature error event to propagate to the TCRIT2 pin |
The mask bits in this register allow control over which error events propagate to the TCRIT3 pin.
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
TCRIT3 Mask | 0×0E | R/W | – | – | – | R4TM | R3TM | R2T2M | R1T2M | LTM | 0×07 |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7-5 | – | RO | Reserved – will report 0 when read. |
4 | R4TM | R/W | Remote 4 Tcrit Mask: 1 – prevents the remote 4 temperature error event from propagating to the TCRIT3 pin 0 – allows the remote 4 temperature error event to propagate to the TCRIT3 pin |
3 | R3TM | R/W | Remote 3 Tcrit Mask: 1 – prevents the remote 3 temperature error event from propagating to the TCRIT3 pin 0 – allows the remote 3 temperature error event to propagate to the TCRIT3 pin |
2 | R2T2M | R/W | Remote 2 Tcrit-2 Mask: 1 – prevents the remote 2 temperature error event from propagating to the TCRIT3 pin 0 – allows the remote 2 temperature error event to propagate to the TCRIT3 pin |
1 | R1T2M | R/W | Remote 1 Tcrit-2 Mask: 1 – prevents the remote 1 temperature error event from propagating to the TCRIT3 pin 0 – allows the remote 1 temperature error event to propagate to the TCRIT3 pin |
0 | LTM | R/W | Local Tcrit Mask: 1 – prevents the local temperature error event from propagating to the TCRIT3 pin 0 – allows the local temperature error event to propagate to the TCRIT3 pin |
The Local Limit register range is 0°C to 127°C. The value programmed in this register is used to determine a local temperature error event.
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Local Tcrit Limit | 0×40 | R/W | 0 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | 0×55 |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7 | 0 | R0 | Read only bit will always report 0. |
6 | 64 | R/W | bit weight 64°C |
5 | 32 | R/W | bit weight 32°C |
4 | 16 | R/W | bit weight 16°C |
3 | 8 | R/W | bit weight 8°C |
2 | 4 | R/W | bit weight 4°C |
1 | 2 | R/W | bit weight 2°C |
0 | 1 | R/W | bit weight 1°C |
The range for these registers is 0°C to 255°C.
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Remote 1 Tcrit-1 Limit (used by TCRIT1 error events) | 0x41 | R/W | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | 0x6E |
Remote 2 Tcrit-1 Limit (used by TCRIT1 error events) | 0x42 | R/W | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | 0x6E |
Remote 3 Tcrit Limit (used by TCRIT1, TCRIT2 and TCRIT3 error events) | 0x43 | R/W | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | 0x55 |
Remote 4 Tcrit Limit (used by TCRIT1, TCRIT2 and TCRIT3 error events) | 0x44 | R/W | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | 0x55 |
Remote 1 Tcrit-2 and Tcrit3 Limit (used by TCRIT2 and TCRIT3 error events) | 0x49 | R/W | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | 0x55 |
Remote 2 Tcrit-2 and Tcrit3 Limit (used by TCRIT2 and TCRIT3 error events) | 0x4A | R/W | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | 0x55 |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7 | 128 | R/W | bit weight 128°C |
6 | 64 | R/W | bit weight 64°C |
5 | 32 | R/W | bit weight 32°C |
4 | 16 | R/W | bit weight 16°C |
3 | 8 | R/W | bit weight 8°C |
2 | 4 | R/W | bit weight 4°C |
1 | 2 | R/W | bit weight 2°C |
0 | 1 | R/W | bit weight 1°C |
Limit assignments for each TCRIT output pin:
OUTPUT PIN | REMOTE 4 | REMOTE 3 | REMOTE 2 | REMOTE 1 | LOCAL |
---|---|---|---|---|---|
TCRIT1 | Remote 4 Tcrit Limit | Remote 3 Tcrit Limit | Remote 2 Tcrit-1 Limit | Remote 1 Tcrit-1 Limit | Local Tcrit Limit |
TCRIT2 | Remote 4 Tcrit Limit | Remote 3 Tcrit Limit | Remote 2 Tcrit-2 Limit | Remote 1 Tcrit-2 Limit | Local Tcrit Limit |
TCRIT3 | Remote 4 Tcrit Limit | Remote 3 Tcrit Limit | Remote 2 Tcrit-2 Limit | Remote 1 Tcrit-2 Limit | Local Tcrit Limit |
The hysteresis register range is 0°C to 32°C. The value programmed in this register is used to modify all the limit values for decreasing temperature.
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Common Tcrit Hysteresis | 0×5A | R/W | 0 | 0 | 0 | 16 | 8 | 4 | 2 | 1 | 0×0A |
Bit(s) | Bit Name | Read/Write | Description |
---|---|---|---|
7 | 0 | RO | Read only bit will always report 0. |
6 | 0 | RO | Read only bit will always report 0. |
5 | 0 | RO | Read only bit will always report 0. |
4 | 16 | R/W | bit weight 16°C |
3 | 8 | R/W | bit weight 8°C |
2 | 4 | R/W | bit weight 4°C |
1 | 2 | R/W | bit weight 2°C |
0 | 1 | R/W | bit weight 1°C |
Register Name | Command Byte (Hex) |
Read/ Write |
D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | POR Default (Hex) |
---|---|---|---|---|---|---|---|---|---|---|---|
Manufacturer ID | 0×FE | RO | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0×01 |
Revision ID | 0×FF | RO | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 0×79 |
NOTE
Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.
The LM95214 can be applied easily in the same way as other integrated-circuit temperature sensors, and its remote diode sensing capability allows it to be used in new ways as well. It can be soldered to a printed-circuit board, and because the path of best thermal conductivity is between the die and the pins, its temperature will effectively be that of the printed-circuit board lands and traces soldered to the LM95214's pins. This presumes that the ambient air temperature is almost the same as the surface temperature of the printed-circuit board; if the air temperature is much higher or lower than the surface temperature, the actual temperature of the LM95214 die will be at an intermediate temperature between the surface and air temperatures. Again, the primary thermal conduction path is through the leads, so the circuit board temperature will contribute to the die temperature much more strongly than will the air temperature.
To measure temperature external to the LM95214's die, incorporates remote diode sensing technology. This diode can be located on the die of a target IC, allowing measurement of the IC's temperature, independent of the LM95214's temperature. A discrete diode can also be used to sense the temperature of external objects or ambient air. Remember that a discrete diode's temperature will be affected, and often dominated, by the temperature of its leads. Most silicon diodes do not lend themselves well to this application. TI recommends that an MMBT3904 transistor base emitter junction be used with the collector tied to the base.
The LM95214 can measure a diode-connected transistor such as the MMBT3904 or the thermal diode found in an AMD processor. The LM95214 has been optimized to measure the MMBT3904 remote thermal diode the offset register can be used to calibrate for other thermal diodes easily. The LM95214 does not include TruTherm™ technology that allows sensing of sub-micron geometry process thermal diodes. For this application the LM95234 would be better suited.
The LM95234 has been specifically optimized to measure the remote thermal diode integrated in a typical Intel processor on 65 nm or 90 nm process or an MMBT3904 transistor. Using the Remote Diode Model Select register found in the LM95234 any of the four remote inputs can be optimized for a typical Intel processor on 65 nm or 90 nm process or an MMBT3904.
The LM95214 operates only as a slave device and communicates with the host through the SMBus serial interface essentially compatible with I2C. SMBCLK is the clock input pin, SMBDATA is a bidirectional data pin, and TCRIT1, TCRIT2, TCRIT3 are the output pins. The LM95214 requires a pullup resistor on the SMBCLK, SMBDATA, and TCRIT1, TCRIT2, TCRIT3 pins due to an open-drain output. It is very important to consider the pullup resistor for the I2C systems. The recommended value for the pullup resistors is in Figure 25. Use a ceramic capacitor type with a temperature rating from –40°C to +125°C, placed as close as possible to the VDD pin of the LM95214. The decoupling capacitor reduces any noise induced by the system. A0 (pin 6) can be connected to either Low, Mid-Supply or High voltages for address selection for configuring three possible unique slave ID addresses; SMBus Interface explains the addressing scheme.
When a transistor is connected as a diode, the following relationship holds for variables VBE, T and IF:
where
In the active region, the –1 term is negligible and may be eliminated, yielding Equation 2
In Equation 2, η and IS are dependant upon the process that was used in the fabrication of the particular diode. By forcing two currents with a very controlled ratio(IF2 / IF1) and measuring the resulting voltage difference, it is possible to eliminate the IS term. Solving for the forward voltage difference yields the relationship:
Solving Equation 3 for temperature yields:
Equation 4 holds true when a diode connected transistor such as the MMBT3904 is used. When this diode equation is applied to an integrated diode such as a processor transistor with its collector tied to GND as shown in Figure 26 it will yield a wide non-ideality spread. This wide non-ideality spread is not due to true process variation but due to the fact that Equation 4 is an approximation.
Texas Instruments invented TruTherm beta cancellation technology that uses the transistor equation, Equation 5, which is a more accurate representation of the topology of the thermal diode found in some sub-micron FPGAs or processors.
TruTherm technology can be found in the LM95234 four channel remote diode sensor that is pin and register compatible with the LM95214. The LM95214 does not support this technology.
The voltage seen by the LM95214 also includes the IFRS voltage drop of the series resistance. The non-ideality factor, η, is the only other parameter not accounted for and depends on the diode that is used for measurement. Because ΔVBE is proportional to both η and T, the variations in η cannot be distinguished from variations in temperature. Because the non-ideality factor is not controlled by the temperature sensor, it will directly add to the inaccuracy of the sensor. For the for Intel processor on 65 nm process, Intel specifies a +4.06%/−0.897% variation in η from part to part when the processor diode is measured by a circuit that assumes diode equation, Equation 4, as true. As an example, assume a temperature sensor has an accuracy specification of ±1.0°C at a temperature of 80°C (353 Kelvin) and the processor diode has a non-ideality variation of +1.19%/−0.27%. The resulting system accuracy of the processor temperature being sensed will be:
and
The next error term to be discussed is that due to the series resistance of the thermal diode and printed-circuit board traces. The thermal diode series resistance is specified on most processor data sheets. For the MMBT3904 transistor, this is specified at 0 Ω typical. The LM95214 accommodates the typical series resistance of a circuit with the offset register compensation. The error that is not accounted for is the spread of the thermal diodes series resistance. If a circuit has a series resistance spread that is 2.79 Ω to 6.24 Ω or 4.515 Ω ±1.73 Ω, the 4.515 Ω can be cancelled out with the offset register setting. The ±1.73 Ω spread cannot be cancelled out. The equation to calculate the temperature error due to series resistance (TER) for the LM95214 is simply:
Solving Equation 6 for RPCB equal to ±1.73 Ω results in the additional error due to the spread in the series resistance of ±1.07°C. The bulk of the error caused by the 4.515 Ω will cause a positive offset in the temperature reading of 2.79°C, which can be cancelled out by setting the offset register to –2.75°C. The spread in error cannot be canceled out, as it would require measuring each individual thermal diode device. This is quite difficult and impractical in a large volume production environment.
Equation 6 can also be used to calculate the additional error caused by series resistance on the printed circuit board. Because the variation of the PCB series resistance is minimal, the bulk of the error term is always positive and can simply be cancelled out by subtracting it from the output readings of the LM95214.
PROCESSOR FAMILY | DIODE EQUATION ηD, non-ideality | SERIES R,Ω | ||
---|---|---|---|---|
MIN | TYP | MAX | ||
Pentium III CPUID 67h | 1 | 1.0065 | 1.0125 | |
Pentium III CPUID 68h/PGA370Socket/ Celeron |
1.0057 | 1.008 | 1.0125 | |
Pentium 4, 423 pin | 0.9933 | 1.0045 | 1.0368 | |
Pentium 4, 478 pin | 0.9933 | 1.0045 | 1.0368 | |
Pentium 4 on 0.13 micron process, 2 - 3.06 GHz | 1.0011 | 1.0021 | 1.0030 | 3.64 |
Pentium 4 on 90 nm process | 1.0083 | 1.011 | 1.023 | 3.33 |
Intel Processor on 65 nm process | 1.000 | 1.009 | 1.050 | 4.52 |
Pentium M (Centrino) | 1.00151 | 1.00220 | 1.00289 | 3.06 |
MMBT3904 | 1.003 | |||
AMD Athlon MP model 6 | 1.002 | 1.008 | 1.016 | |
AMD Athlon 64 | 1.008 | 1.008 | 1.096 | |
AMD Opteron | 1.008 | 1.008 | 1.096 | |
AMD Sempron | 1.00261 | 0.93 |
To compensate for the errors introduced by non-ideality, the temperature sensor is calibrated for a particular processor. Texas Instruments temperature sensors are always calibrated to the typical non-ideality and series resistance of a given transistor type. The LM95214 is calibrated for the non-ideality factor and series resistance values of the MMBT3904 transistor without the requirement for additional trims. When a temperature sensor calibrated for a particular thermal diode type is used with a different thermal diode type, additional errors are introduced.
Temperature errors associated with non-ideality of different processor types may be reduced in a specific temperature range of concern through use of software calibration. Typical Non-ideality specification differences cause a gain variation of the transfer function, therefore the center of the temperature range of interest must be the target temperature for calibration purposes. The Equation 7 can be used to calculate the temperature correction factor (TCF) required to compensate for a target non-ideality differing from that supported by the LM95214.
where
The correction factor must be directly added to the temperature reading produced by the LM95214. For example when using the LM95214, with the 3904 mode selected, to measure a AMD Athlon processor, with a typical non-ideality of 1.008, for a temperature range of 60°C to 100°C the correction factor would calculate to:
Therefore, 1.75°C must be subtracted from the temperature readings of the LM95214 to compensate for the differing typical non-ideality target.