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TPS82130: Pre-biased Output Condition

ReedKacz
Expert 3462 points
Part Number: TPS82130

Hi Power Experts,

I have a use case where the TPS82130 is generating a 2.5V output. The enable is connected to the VIN supply. The device can be running and fully charge the output capacitors to 2.5V and then lose input power.

Once the device is disabled, the power returns to VIN = 5V. Then the device will operate by monotonically rising the reference voltage and once that hits parity with VOUT, then the MOSFET will re-engage and regulate the voltage. Is that understanding correct?

My next question is: when VOUT = 2.5V and VIN = 0V - will the body diode of the high-side FET conduct and actively discharge VOUT?

Thanks,

Reed

  • 0
    TI__Guru 50120 points

    Hi Reed,

    It sounds like you are doing a power cycle on your input power supply of 5V.

    When the device is disabled by pulling EN low, the device will stop switching even with a valid input voltage. Only after pulling EN high will the device enable and begin its power-up sequence. During power-up the device has to clear the UVLO threshold to even start the part up. When the power returns it will ramp from 0V to 5V, and the device may momentarily enter low dropout operation (100% duty cycle). Depending on how fast the slew rate of your 5V power supply is, the device may be in low dropout operation for a longer period of time, of which the high-side MOSFET is constantly turned on.

    However in your case of 5V input to 2.5V output, the device will eventually clear low dropout operation and resume regular operation at either PFM or PWM mode depending on your load current. When your input voltage stabilize at 5V and output is regulated to 2.5V, the high-side and low-side MOSFET will alternate at a 50% duty cycle.

    When VOUT = 2.5V and VIN = 0V, the output voltage will primarily discharge through the output capacitors. This discharge can be further accelerated by having a bleeding resistor on the output if you want to have VOUT drop to 0V sooner.

    Regards,

    Jimmy