The LM61 device is a precision, integrated-circuit temperature sensor that can sense a –30°C to 100°C temperature range while operating from a single 2.7‑V supply. The output voltage of the LM61 is linearly proportional to temperature (10 mV/°C) and has a DC offset of 600 mV. The offset allows reading negative temperatures without the need for a negative supply. The nominal output voltage of the LM61 ranges from 300 mV to 1600 mV for a –30°C to 100°C temperature range. The LM61 is calibrated to provide accuracies of ±2°C at room temperature and ±3°C over the full –25°C to 85°C temperature range.
The linear output of the LM61, 600-mV offset, and factory calibration simplify external circuitry required in a single supply environment where reading negative temperatures is required. Because the quiescent current is less than 125 µA, self-heating is limited to a very low 0.2°C in still air. Shutdown capability for the LM61 is intrinsic because its inherent low power consumption allows it to be powered directly from the output of many logic gates.
PART NUMBER | PACKAGE | BODY SIZE (NOM) |
---|---|---|
LM61 | SOT-23 (3) | 1.30 mm × 2.92 mm |
TO-92 (3) | 4.30 mm × 4.30 mm |
VALUE | |
---|---|
Accuracy at 25°C | ±2°C or ±3°C |
Accuracy for –25°C to 85°C | ±3°C |
Accuracy for –30°C to 100°C | ±4°C |
Temperature slope | 10 mV/°C |
Power supply voltage | 2.7 V to 10 V |
Current drain at 25°C | 125 µA |
Nonlinearity | ±0.8°C |
Output impedance | 800 Ω |
Changes from I Revision (February 2013) to J Revision
Changes from H Revision (February 2013) to I Revision
PIN | TYPE | DESCRIPTION | |
---|---|---|---|
NAME | NO. | ||
+VS | 1 | Power | Positive power supply pin. |
VOUT | 2 | Output | Temperature sensor analog output. |
GND | 3 | Ground | Device ground pin, connected to power supply negative terminal. |
MIN | MAX | UNIT | |
---|---|---|---|
Supply voltage | 12 | –0.2 | V |
Output voltage | (+VS + 0.6) | –0.6 | V |
Output current | 10 | mA | |
Input current at any pin(2) | 5 | mA | |
Maximum junction temperature, TJ | 125 | °C | |
Storage temperature, Tstg | –65 | 150 | °C |
VALUE | UNIT | |||
---|---|---|---|---|
V(ESD) | Electrostatic discharge | Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1)(2) | ±2500 | V |
Machine Model (MM)(3) | ±250 |
MIN | MAX | UNIT | |||
---|---|---|---|---|---|
+VS | Supply voltage | 2 | 10 | V | |
T | Operating temperature | LM61C | –30 | 100 | °C |
LM61B | –25 | 85 |
THERMAL METRIC(1) | LM61 | UNIT | ||
---|---|---|---|---|
DBZ (SOT-23) | LP (TO-92) | |||
3 PINS | 3 PINS | |||
RθJA | Junction-to-ambient thermal resistance(2) | 286.3 | 162.2 | °C/W |
RθJC(top) | Junction-to-case (top) thermal resistance | 96 | 85 | °C/W |
RθJB | Junction-to-board thermal resistance | 57.1 | — | °C/W |
ψJT | Junction-to-top characterization parameter | 5.3 | 29.2 | °C/W |
ψJB | Junction-to-board characterization parameter | 55.8 | 141.4 | °C/W |
PARAMETER | TEST CONDITIONS | MIN(3) | TYP(4) | MAX(3) | UNIT | |
---|---|---|---|---|---|---|
Accuracy(5) | TA = 25°C | LM61B | –2 | 2 | °C | |
LM61C | –3 | 3 | ||||
LM61B | –3 | 3 | ||||
LM61C | –4 | 4 | ||||
Output voltage at 0°C | 600 | mV | ||||
Nonlinearity(6) | LM61B | –0.6 | 0.6 | °C | ||
LM61C | –0.8 | 0.8 | ||||
Sensor gain (average slope) | LM61B | 9.7 | 10 | 10.3 | mV/°C | |
LM61C | 9.6 | 10 | 10.4 | |||
Output impedance | +VS = 3 V to 10 V | 0.8 | kΩ | |||
TA = –30°C to 85°C, +VS = 2.7 V | 2.3 | |||||
TA = 85°C to 100°C, +VS = 2.7 V | 5 | |||||
Line regulation(7) | +VS = 3 V to 10 V | –0.7 | 0.7 | mV/V | ||
+VS = 2.7 V to 3.3 V | –5.7 | 5.7 | mV | |||
Quiescent current | +VS = 2.7 V to 10 V | TA = 25°C | 82 | 125 | µA | |
155 | ||||||
Change of quiescent current | +VS = 2.7 V to 10 V | ±5 | µA | |||
Temperature coefficient of quiescent current | 0.2 | µA/°C | ||||
Long term stability(8) | TJ = TMAX = 100°C, for 1000 hours | ±0.2 | °C |
The LM61 is a precision integrated-circuit temperature sensor that can sense a –30°C to 100°C temperature range using a single positive supply. The output voltage of the LM61 has a positive temperature slope of
10 mV/°C. A 600-mV offset is included, enabling negative temperature sensing when biased by a single supply. The temperature-sensing element is comprised of a delta-VBE architecture. The temperature-sensing element is then buffered by an amplifier and provided to the VOUT pin. The amplifier has a simple class A output stage as shown in Functional Block Diagram.
The LM61 follows a simple linear transfer function to achieve the accuracy as listed in Electrical Characteristics. Use Equation 1 to calculate the value of VO.
where
The only functional mode of the LM61 device is an analog output directly proportional to temperature.
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 LM61 has a wide supply range and a 10-mV/°C output slope with a 600-mV DC. Therefore, it can be easily applied in many temperature-sensing applications where a single supply is required for positive and negative temperatures.
For this design example, use the parameters listed in Table 1 as the input parameters.
PARAMETER | VALUE |
---|---|
Power supply voltage | 2.7 V to 3.3 V |
Accuracy at 25°C | ±2°C (maximum) |
Accuracy over –25°C to 85°C | ±3°C (maximum) |
Temperature slope | 10 mV/°C |
The LM61 is a simple temperature sensor that provides an analog output. Therefore, design requirements related to layout outweigh other requirements in importance. See Layout for more information.
The LM61 handles capacitive loading well. Without any special precautions, the LM61 can drive any capacitive load as shown in Figure 12. Over the specified temperature range the LM61 has a maximum output impedance of 5 kΩ. In an extremely noisy environment it may be necessary to add some filtering to minimize noise pickup. It is recommended that 0.1-µF capacitor be added between +VS and GND to bypass the power-supply voltage, as shown in Figure 13. In a noisy environment it may be necessary to add a capacitor from VOUT to ground. A 1-µF output capacitor with the 5-kΩ maximum output impedance forms a 32-Hz lowpass filter. Because the thermal time constant of the LM61 is much slower than the 5-ms time constant formed by the RC, the overall response time of the LM61 is not significantly affected. For much larger capacitors this additional time lag increases the overall response time of the LM61.
Figure 15 shows an application circuit example using the LM61 device. Customers must fully validate and test any circuit before implementing a design based on an example in this section. Unless otherwise noted, the design procedures in Typical Temperature Sensing Circuit are applicable.
In an extremely noisy environment, it may be necessary to add filtering to minimize noise pickup. TI recommends a 0.1-µF capacitor be added between +VS to GND to bypass the power-supply voltage, as shown in Figure 13.
The LM61 can be applied easily in the same way as other integrated-circuit temperature sensors. It can be glued or cemented to a surface. The temperature that the LM61 senses is within about 0.2°C of the surface temperature that LM61's leads are attached to.
This presumes that the ambient air temperature is almost the same as the surface temperature; if the air temperature is much higher or lower than the surface temperature, the actual temperature measured would be at an intermediate temperature between the surface temperature and the air temperatures.
To ensure good thermal conductivity the backside of the LM61 die is directly attached to the GND pin. The lands and traces to the LM61 are part of the printed-circuit board, which is the object whose temperature is being measured.
Alternatively, the LM61 can be mounted inside a sealed-end metal tube, and can then be dipped into a bath or screwed into a threaded hole in a tank. As with any IC, the LM61 and accompanying wiring and circuits must be kept insulated and dry, to avoid leakage and corrosion. This is especially true if the circuit may operate at cold temperatures where condensation can occur. Printed-circuit coatings and varnishes such as Humiseal and epoxy paints or dips are often used to ensure that moisture cannot corrode the device or connections.
The junction-to-ambient thermal resistance is the parameter used to calculate the rise of a device junction temperature due to its power dissipation. For the LM61, Equation 2 is used to calculate the rise in the die temperature.
where
Table 2 summarizes the rise in die temperature of the LM61 without any loading with a 3.3-V supply, and the thermal resistance for different conditions.
RθJA (°C/W) | TJ – TA (°C) | |||
---|---|---|---|---|
SOT-23 | No heat sink(1) | Still air | 450 | 0.26 |
Moving air | — | — | ||
Small heat fin(2) | Still air | 260 | 0.13 | |
Moving air | 180 | 0.09 | ||
TO-92 | No heat sink(1) | Still air | 180 | 0.09 |
Moving air | 90 | 0.05 | ||
Small heat fin(3) | Still air | 140 | 0.07 | |
Moving air | 70 | 0.03 |
TEMPERATURE | VO(TYPICAL) |
---|---|
100°C | 1600 mV |
85°C | 1450 mV |
25°C | 850 mV |
0°C | 600 mV |
–25°C | 350 mV |
–30°C | 300 mV |
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