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TPS54394: PG1 and PG2 sink current capability

K. Sasaki14
Guru 10200 points
Part Number: TPS54394

Can TPS54394 PG1 and PG2 sink 10mA?

Our customer are thinking to use two LEDs, one LED cathode is connected to PG1 and another cathode is connected to PG2, and each LED anode is pull-up to VREG5 (pull-up resistor is 470 ohm).
Each LED current is about 10mA.

Best Regards,
Kohei Sasaki

  • 0
    TI__Genius 9550 points
    Kohei,
    VREG5 is only for IC internal circuit, can't be used for exernal circuit.
    PG1/2 is designed for signal control (normally <1mA). Do not support to sink 10mA. Suggest use PG1/2 signal to control Fet or transistor, then sink/source LED current.
  • 0
    TI__Expert 4875 points
    Hi Kohei,

    Could you let us know why do you plan to use PG to control the LED? Does the LED use to indicate power not good for the device? I checked on the datasheet and found when PG=low, if assuming 10mA current sinking to PG, then PG voltage will be from 0.5V to 1.1V. For VREG5 pin, it is the output voltage of internal regulator which will supply gate drive voltage for high side FET. As Jason said, it is critical to circuit operation so it is not recommended to connect with.
  • 0 in reply to Anthony Lang
    Guru 10200 points
    Anthony-san,

    Yes, LED is used as indicator of power not good.
    I understood it is not recommended, however we can use VREG5 as pull-up source such as PG which does not sink large current.
    Is it allowed until a few mA?

    Best Regards,
    Kohei Sasaki
  • 0 in reply to K. Sasaki14
    TI__Expert 4875 points

    Hi Kohei-san,

    Actually, some other customer would like to use this device VREG5 to drive a MOSFET. I have worked with our ATE team to check the IV curves for this regulator. You could see the current limit level is aournd 25mA and the VREG5 will drop to around 4.3V. You could do some validation on your bench but we will not guarantee you that there is no risk for this kind of use.

  • 0 in reply to Anthony Lang
    TI__Expert 4875 points
    Hi Kohei-san,

    Sorry that I got a typo. The curve is not exactly from this device but from the similar device that we support. Thanks!