SNVS999 May 2014 LM10507
PRODUCTION DATA.
LM10507 is a highly efficient and integrated Power Management Unit for Systems-on-a-Chip (SoCs), ASICs, and processors. It operates cooperatively and communicates with processors over an SPI interface with output Voltage programmability and Standby Mode. The device incorporates three high-efficiency synchronous buck regulators and one LDO that deliver four output voltages from a single power source. The device also includes a SPI-programmable Comparator Block that provides an interrupt output signal
A buck converter contains a control block, a switching PFET connected between input and output, a synchronous rectifying NFET connected between the output and ground and a feedback path. The following figure shows the block diagram of each of the three buck regulators integrated in the device.
During the first portion of each switching cycle, the control block turns on the internal PFET switch. This allows current to flow from the input through the inductor to the output filter capacitor and load. The inductor limits the current to a ramp with a slope of (VIN – VOUT)/L by storing energy in a magnetic field. During the second portion of each cycle, the control block turns the PFET switch off, blocking current flow from the input, and then turns the NFET synchronous rectifier on. The inductor draws current from ground through the NFET to the output filter capacitor and load, which ramps the inductor current down with a slope of (–VOUT)/L.
The output filter stores charge when the inductor current is high, and releases it when low, smoothing the voltage across the load. The output voltage is regulated by modulating the PFET switch on time to control the average current sent to the load. The effect is identical to sending a duty-cycle modulated rectangular wave formed by the switch and synchronous rectifier at the SW pinto a low-pass filter formed by the inductor and output filter capacitor. The output voltage is equal to the average voltage at the SW terminal.
The LM10507 incorporates three high-efficiency synchronous switching buck regulators that deliver various voltages from a single DC input voltage. They include many advanced features to achieve excellent voltage regulation, high efficiency and fast transient response time. The bucks feature voltage mode architecture with synchronous rectification.
Each of the switching regulators is specially designed for high-efficiency operation throughout the load range. With a 2MHz typical switching frequency, the external L- C filter can be small and still provide very low output voltage ripple. The bucks are internally compensated to be stable with the recommended external inductors and capacitors as detailed in the application diagram. Synchronous rectification yields high efficiency for low voltage and high output currents.
All bucks can operate up to a 100% duty cycle allowing for the lowest possible input voltage that still maintains the regulation of the output. The lowest input to output dropout voltage is achieved by keeping the PMOS switch on.
Additional features include soft-start, undervoltage lockout, bypass, and current and thermal overload protection. To reduce the input current ripple, the device employs a control circuit that operates the 3 bucks at 120° phase. These bucks are nearly identical in performance and mode of operation. They can operate in FPWM (forced PWM) or automatic mode (PWM/PFM).
During PWM operation the converter operates as a voltage-mode controller with input voltage feed forward. This allows the converter to achieve excellent load and line regulation. The DC gain of the power stage is proportional to the input voltage. To eliminate this dependence, a feed forward voltage inversely proportional to the input voltage is introduced.
In Forced PWM Mode the bucks always operate in PWM mode regardless of the output current.
In Automatic Mode, if the output current is less than 70 mA (typ.), the bucks automatically transition into PFM (Pulse Frequency Modulation) operation to reduce the current consumption. At higher than 70 mA (typ.) they operate in PWM mode. This increases the efficiency at lower output currents.
At very light loads, Bucks 1, 2, and Buck 3 enter PFM mode and operate with reduced switching frequency and supply current to maintain high efficiency.
Bucks 1, 2 and 3 will automatically transition into PFM mode when either of two conditions occurs for a duration of 32 or more clock cycles:
During PFM operation, the converter positions the output voltage slightly higher than the nominal output voltage during PWM operation, allowing additional headroom for voltage drop during a load transient from light to heavy load. The PFM comparators sense the output voltage via the feedback pinand control the switching of the output FETs such that the output voltage ramps between 0.8% and 1.6% (typical) above the nominal PWM output voltage. If the output voltage is below the ‘high’ PFM comparator threshold, the PMOS power switch is turned on. It remains on until the output voltage exceeds the ‘high’ PFM threshold or the peak current exceeds the IPFM level set for PFM mode.
Once the PMOS power switch is turned off, the NMOS power switch is turned on until the inductor current ramps to zero. When the NMOS zero-current condition is detected, the NMOS power switch is turned off. If the output voltage is below the ‘high’ PFM comparator threshold (see Figure 7), the PMOS switch is again turned on and the cycle is repeated until the output reaches the desired level. Once the output reaches the ‘high’ PFM threshold, the NMOS switch is turned on briefly to ramp the inductor current to zero and then both output switches are turned off and the part enters an extremely low power mode. Quiescent supply current during this ‘idle’ mode is less than 100 µA, which allows the part to achieve high efficiencies under extremely light load conditions. When the output drops below the ‘low’ PFM threshold, the cycle repeats to restore the output voltage to ~1.6% above the nominal PWM output voltage.
If the load current should increase during PFM mode causing the output voltage to fall below the ‘low2’ PFM threshold, the part will automatically transition into fixed-frequency PWM mode.
Each of the buck converters has an internal soft-start circuit that limits the in-rush current during startup. This allows the converters to gradually reach the steady-state operating point, thus reducing startup stresses and surges. During startup, the switch current limit is increased in steps.
For Bucks 1, 2 and 3 the soft start is implemented by increasing the switch current limit in steps that are gradually set higher. The startup time depends on the output capacitor size, load current and output voltage. Typical startup time with the recommended output capacitor of 10 µF is 0.1-0.5ms. It is expected that in the final application the load current condition will be more likely in the lower load current range during the startup.
A current limit feature protects the device and any external components during overload conditions. In PWM mode the current limiting is implemented by using an internal comparator that trips at current levels according to the buck capability. If the output is shorted to ground the device enters a timed current limit mode where the NFET is turned on for a longer duration until the inductor current falls below a low threshold, ensuring inductor current has more time to decay, thereby preventing runaway.
While in PWM mode, the bucks use an internal NFET as a synchronous rectifier to reduce the rectifier forward voltage drop and the associated power loss. Synchronous rectification provides a significant improvement in efficiency whenever the output voltage is relatively low compared to the voltage drop across an ordinary rectifier diode.
The device can operate at 100% duty cycle (no switching; PMOS switch completely on) for low dropout support. In this way the output voltage will be controlled down to the lowest possible input voltage. When the device operates near 100% duty cycle, output voltage ripple is approximately 25 mV.
The minimum input voltage needed to support the output voltage:
where
Once VVIN reaches the UVLO threshold and the ENABLE pin= High the LM10507 will start up. There is a fixed delay of approx. 1 ms before the LDO starts up, followed by Buck1 at 1ms. After a delay of 1msec from Buck1, Buck2 and Buck3 regulators start together. There is a maximum of 500us soft-start with full load for the Bucks
The Startup Sequence will be:
The device will be enabled over the ENABLE terminal, unless outside of operating voltage range. Once VVIN reaches a minimum required input Voltage and ENABLE=High the power-up sequence will be started. Once the device is started, the output voltage of the Bucks can be individually disabled by accessing their corresponding BK1EN, BK2EN register bits (BUCK CONTROL).
The RESET pinis internally pulled up. If the RESET pinis set low, the device will perform a complete reset of all the registers to their default states. This means that all of the voltage settings on the regulators will go back to their default state and all Regulators will be turned ON. All Registers will be set back to default instantaneously but no Start-Up Sequence initiated like it would be with ENABLE terminal.
The Device can be programmed into Standby mode. There are 2 ways for doing that:
When the DEVSLP pinis asserted high, the LM10507 will enter Device Sleep Mode. While in Device Sleep Mode, all Regulator outputs are turned OFF except Buck3. Note: Bucks1,2 and LDO will turn off when the DEVSLP signal is given. All disabled output Rails will turn off immediately and at the same time (no sequencing). An internal 22 kΩ (typ.) pull down resistor is attached to the FB pinof Buck 1 and Buck2. Buck 1 and 2 outputs are pulled to ground level when they are disabled to discharge any residual charge present in the output circuitry. When Device Sleep transitions to a low, Buck 1, Buck2 and LDO are enabled. Buck 3 will go back to its previous state
There is no bit which has the same function as DEVSLP terminal. Disabling or programming the Bucks to new level is the user’s decision based on power consumption and other requirements
The following section describes how to program the chip into Device Sleep Mode corresponding to DEVSLP pinfunction: Buck 3 must be PFM. To program the LM10507 to Device Sleep Mode via SPI, Buck 1 and Buck2 must be disabled by host device (Register 0x0A bit 0). The LDO must be disabled (Register 0x0B bit 1 and 0). Then stop the oscillator (Register 0x0E bit 1) To wake LM10507 from Device Sleep Mode, reverse this sequence.
The ENABLE pinis a digital function to control the Start-Up of PMIC. ENABLE has an internal pull-down and is active High. A pull-down resistor is connected to GND. Transitions of the ENABLE pinto Low during device operation will disable all regulators and actively force down all the output voltages. Register defaults are restored while ENABLE is low.
The VIN voltage is monitored for a supply under voltage condition, for which the operation of the device cannot be guaranteed. The part will automatically disable PMIC. To prevent unstable operation, the UVLO has a hysteresis window of about 300mV. An under voltage lockout (UVLO) will disable all buck outputs, all internal registers are reset. Once the supply voltage is above the UVLO hysteresis, the device will initiate a power-up sequence and then enter the active state.
The LDO will remain functional past the UVLO threshold until VVIN reaches approximately 2.25V.
The VIN voltage is monitored for a supply over voltage condition, for which the operation of the device cannot be guaranteed. The purpose of OVLO is to protect the part and all other components connected to the PMU outputs from any damage and malfunction. Once VVIN rises over about 5.8V all the Bucks and LDO will be disabled automatically. To prevent unstable operation, the OVLO has a hysteresis window of about 100mV. An over voltage lockout (OVLO) will force the device into the reset state, all internal registers are reset. Once the supply voltage goes below the OVLO lower threshold, the device will initiate a power-up sequence and then enter the active state. Operating maximum input voltage at which parameters are guaranteed is 5.5 V. Absolute maximum of the device is 6.0 V.
The LM10507 has PWR_OK pinto signal that all output rails are valid. PWR_OK is Low if Buck3 is disabled in register0x0A. If PWR_OK condition is detected, then the Hardware PWR_OK pinwill be set immediately. There are four PWR_OK generating conditions, all must be fulfilled :
NOTE
SPI commanded Disable of any output, followed by a subsequent SPI commanded ENABLE will cause a temporary logic LOW of the PWR_OK pinuntil that Buck output voltage has risen back to the 90% flag level.
The temperature of the silicon die is monitored for an over-temperature condition, for which the operation of the device cannot be guaranteed. The part will automatically be disabled if the temperature is too high. The thermal shutdown (TSD) will force the device into the reset state. In reset, all circuitry is disabled. To prevent unstable operation, the TSD has a hysteresis window of about 20۫°C. Once the temperature has decreased below the TSD hysteresis, the device will initiate a power-up sequence and then enter the active state. In the active state, the part will start up as if for the first time, all registers will be in their default state.
The device is programmable via 4-wire SPI Interface. The signals associated with this interface are CS, DI, DO and CLK. Through this interface, the user can enable/disable the device, program the output voltages of the individual bucks and of course read the status of Flag registers.
By accessing the registers in the device through this interface, the user can get access and control the operation of the buck controllers and program the reference voltage of the comparator in the device.
Addr | Reg Name | Bit | R/W | Default | Description | Notes |
---|---|---|---|---|---|---|
0x00 | Buck 3 Voltage | 7 | — | — | Reset default: | |
0x7F (1.5 V) | ||||||
6 | R/W | 1 | Buck 3 Voltage Code[6] | Range: 0.865-1.5 V | ||
5 | R/W | 1 | Buck 3 Voltage Code[5] | |||
4 | R/W | 1 | Buck 3 Voltage Code[4] | |||
3 | R/W | 1 | Buck 3 Voltage Code[3] | |||
2 | R/W | 1 | Buck 3 Voltage Code[2] | |||
1 | R/W | 1 | Buck 3 Voltage Code[1] | |||
0 | R/W | 1 | Buck 3 Voltage Code[0] | |||
0x07 | Buck 1 Voltage | 7 | — | — | — | Reset default: |
6 | — | — | 0x12 (1.8 V) | |||
5 | R/W | 0 | Buck 1 Voltage Code[5] | |||
4 | R/W | 1 | Buck 1 Voltage Code[4] | Range: 0.9-3.4 | ||
3 | R/W | 0 | Buck 1 Voltage Code[3] | |||
2 | R/W | 0 | Buck 1 Voltage Code[2] | |||
1 | R/W | 1 | Buck 1 Voltage Code[1] | |||
0 | R/W | 0 | Buck 1 Voltage Code[0] | |||
0x08 | Buck 2 Voltage | 7 | — | — | — | Reset default: |
6 | — | — | — | 0x12 (1.8 V) | ||
5 | R/W | 0 | Buck 2 Voltage Code[5] | |||
4 | R/W | 1 | Buck 2 Voltage Code[4] | Range: 0.9-3.4 | ||
3 | R/W | 0 | Buck 2 Voltage Code[3] | |||
2 | R/W | 0 | Buck 2 Voltage Code[2] | |||
1 | R/W | 1 | Buck 2 Voltage Code[1] | |||
0 | R/W | 0 | Buck 2 Voltage Code[0] | |||
0x09 | DevSLP Mode Voltage for Buck 3 | 7 | R/W | — | — | Reset default: |
6 | R/W | 1 | Buck 3 Voltage Code[6] | 0x7F (1.5 V) | ||
5 | R/W | 1 | Buck 3 Voltage Code[5] | |||
4 | R/W | 1 | Buck 3 Voltage Code[4] | |||
3 | R/W | 1 | Buck 3 Voltage Code[3] | |||
2 | R/W | 1 | Buck 3 Voltage Code[2] | |||
1 | R/W | 1 | Buck 3 Voltage Code[1] | |||
0 | R/W | 1 | Buck 3 Voltage Code[0] | |||
0x0A | Buck Control | 7 | R/W | 1 | BK3EN | Enable/Disable Buck 3 |
6 | — | — | — | |||
5 | — | — | — | |||
4 | R/W | — | BK1FPWM | Buck 1 forced PWM mode when high | ||
3 | R/W | 0 | BK2FPWM | Buck 2 forced PWM mode when high | ||
2 | R/W | 0 | BK3FPWM | Buck 3 forced PWM mode when high | ||
1 | R/W | 1 | BK1EN | Enables Buck 1 0-disabled, 1-enabled | ||
0 | R/W | 1 | BK2EN | Enables Buck 2 0-disabled, 1-enabled | ||
0x0B | LDO Control | 7 | — | — | — | |
6 | — | — | — | |||
5 | — | — | — | |||
4 | — | — | — | |||
3 | — | — | — | |||
2 | — | — | — | |||
1 | — | — | — | |||
0 | R/W | 1 | LDO Enable | |||
0x0D | Status | 7 | — | |||
6 | — | |||||
5 | — | |||||
4 | R | LDO OK | LDO is greater than 90% of target | |||
3 | R | Buck 3 OK | Buck 3 is greater than 90% of target | |||
2 | R | Buck 2 OK | Buck 2 is greater than 90% of target | |||
1 | R | Buck 1 OK | Buck 1 is greater than 90% of target | |||
0 | R | PWR_OK | PWR_OK output is high | |||
0x0E | MISC Control | 7 | — | |||
6 | — | |||||
5 | — | |||||
4 | — | |||||
3 | — | |||||
2 | — | |||||
1 | R/W | 0 | Oscillator Disable | OSC ENABLE/DISABLE | ||
0 |
Voltage Code | Voltage | Voltage Code | Voltage |
---|---|---|---|
0x00 | 0.9 | 0x20 | 2.5 |
0x01 | 0.95 | 0x21 | 2.55 |
0x02 | 1 | 0x22 | 2.6 |
0x03 | 1.05 | 0x23 | 2.65 |
0x04 | 1.1 | 0x24 | 2.7 |
0x05 | 1.15 | 0x25 | 2.75 |
0x06 | 1.2 | 0x26 | 2.8 |
0x07 | 1.25 | 0x27 | 2.85 |
0x08 | 1.3 | 0x28 | 2.9 |
0x09 | 1.35 | 0x29 | 2.95 |
0x0A | 1.4 | 0x2A | 3 |
0x0B | 1.45 | 0x2B | 3.05 |
0x0C | 1.5 | 0x2C | 3.1 |
0x0D | 1.55 | 0x2D | 3.15 |
0x0E | 1.6 | 0x2E | 3.2 |
0x0F | 1.65 | 0x2F | 3.25 |
0x10 | 1.7 | 0x30 | 3.3 |
0x11 | 1.75 | 0x31 | 3.35 |
0x12 | 1.8 | 0x32 | 3.4 |
0x13 | 1.85 | 0x33 | 3.4 |
0x14 | 1.9 | 0x34 | 3.4 |
0x15 | 1.95 | 0x35 | 3.4 |
0x16 | 2 | 0x36 | 3.4 |
0x17 | 2.05 | 0x37 | 3.4 |
0x18 | 2.1 | 0x38 | 3.4 |
0x19 | 2.15 | 0x39 | 3.4 |
0x1A | 2.2 | 0x3A | 3.4 |
0x1B | 2.25 | 0x3B | 3.4 |
0x1C | 2.3 | 0x3C | 3.4 |
0x1D | 2.35 | 0x3D | 3.4 |
0x1E | 2.4 | 0x3E | 3.4 |
0x1F | 2.45 | 0x3F | 3.4 |
Voltage Code | Voltage | Voltage Code | Voltage | Voltage Code | Voltage | Voltage Code | Voltage |
---|---|---|---|---|---|---|---|
0x00 | 0.865 | 0x20 | 1.025 | 0x40 | 1.185 | 0x60 | 1.345 |
0x01 | 0.87 | 0x21 | 1.03 | 0x41 | 1.19 | 0x61 | 1.35 |
0x02 | 0.875 | 0x22 | 1.035 | 0x42 | 1.195 | 0x62 | 1.355 |
0x03 | 0.88 | 0x23 | 1.04 | 0x43 | 1.2 | 0x63 | 1.36 |
0x04 | 0.885 | 0x24 | 1.045 | 0x44 | 1.205 | 0x64 | 1.365 |
0x05 | 0.89 | 0x25 | 1.05 | 0x45 | 1.21 | 0x65 | 1.37 |
0x06 | 0.895 | 0x26 | 1.055 | 0x46 | 1.215 | 0x66 | 1.375 |
0x07 | 0.9 | 0x27 | 1.06 | 0x47 | 1.22 | 0x67 | 1.38 |
0x08 | 0.905 | 0x28 | 1.065 | 0x48 | 1.225 | 0x68 | 1.385 |
0x09 | 0.91 | 0x29 | 1.07 | 0x49 | 1.23 | 0x69 | 1.39 |
0x0A | 0.915 | 0x2A | 1.075 | 0x4A | 1.235 | 0x6A | 1.395 |
0x0B | 0.92 | 0x2B | 1.08 | 0x4B | 1.24 | 0x6B | 1.4 |
0x0C | 0.925 | 0x2C | 1.085 | 0x4C | 1.245 | 0x6C | 1.405 |
0x0D | 0.93 | 0x2D | 1.09 | 0x4D | 1.25 | 0x6D | 1.41 |
0x0E | 0.935 | 0x2E | 1.095 | 0x4E | 1.255 | 0x6E | 1.415 |
0x0F | 0.94 | 0x2F | 1.1 | 0x4F | 1.26 | 0x6F | 1.42 |
0x10 | 0.945 | 0x30 | 1.105 | 0x50 | 1.265 | 0x70 | 1.425 |
0x11 | 0.95 | 0x31 | 1.11 | 0x51 | 1.27 | 0x71 | 1.43 |
0x12 | 0.955 | 0x32 | 1.115 | 0x52 | 1.275 | 0x72 | 1.435 |
0x13 | 0.96 | 0x33 | 1.12 | 0x53 | 1.28 | 0x73 | 1.44 |
0x14 | 0.965 | 0x34 | 1.125 | 0x54 | 1.285 | 0x74 | 1.445 |
0x15 | 0.97 | 0x35 | 1.13 | 0x55 | 1.29 | 0x75 | 1.45 |
0x16 | 0.975 | 0x36 | 1.135 | 0x56 | 1.295 | 0x76 | 1.455 |
0x17 | 0.98 | 0x37 | 1.14 | 0x57 | 1.3 | 0x77 | 1.46 |
0x18 | 0.985 | 0x38 | 1.145 | 0x58 | 1.305 | 0x78 | 1.465 |
0x19 | 0.99 | 0x39 | 1.15 | 0x59 | 1.31 | 0x79 | 1.47 |
0x1A | 0.995 | 0x3A | 1.155 | 0x5A | 1.315 | 0x7A | 1.475 |
0x1B | 1 | 0x3B | 1.16 | 0x5B | 1.32 | 0x7B | 1.48 |
0x1C | 1.005 | 0x3C | 1.165 | 0x5C | 1.325 | 0x7C | 1.485 |
0x1D | 1.01 | 0x3D | 1.17 | 0x5D | 1.33 | 0x7D | 1.49 |
0x1E | 1.015 | 0x3E | 1.175 | 0x5E | 1.335 | 0x7E | 1.495 |
0x1F | 1.02 | 0x3F | 1.18 | 0x5F | 1.34 | 0x7F | 1.5 |