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TPS65224-Q1: Operating conditions of TPS65224 discharge resistance

Nakayama Kentaro
Expert 1385 points
Part Number: TPS65224-Q1

Hello Experts,

Let me confirm two things about the operating conditions of the discharge resistance of the BUCK.

(1) If the input voltage of the BUCK drops to 0V instantaneously, will the discharge resistor work?

(2) When the BUCK is not operating, is the discharge resistor enabled?

Regards,

Kentaro

  • +1
    TI__Mastermind 19780 points

    Hi Kentaro,

    (1) As the VCCA is often the input for the BUCKs then this will depend on the output and input capacitance as well. If the PMIC loses VCCA then the pull-down might not be enabled for long enough to completely discharge the BUCK output. If there is a lot of output capacitance then it will take longer to discharge the output. It is thus recommended to disable all the outputs before the PMIC loses VCCA so that the PMIC can shut down all the regulators properly. Of course this can't always be predicted.

    (2) If the bit BUCKx_PLDN = 1 then the pull-down resistor will be enabled only when the BUCK is switched off.

    regards,

    Niko

  • 0 in reply to Niko Alatalo
    Expert 1385 points

    Hi Niko,

    Thanks for the quick answer.

    (1)

    Niko Alatalo said:
    If the PMIC loses VCCA then the pull-down might not be enabled for long enough to completely discharge the BUCK output

    In this case, does it mean that the discharge resistor will be disabled when VCCA is lost, and the voltage of BUCK may not be 0V?

    (2) I understand the following contents.

    Niko Alatalo said:

    If the bit BUCKx_PLDN = 1 then the pull-down resistor will be enabled only when the BUCK is switched off.

    regards,

    Regards,

    Kentaro

  • +1 in reply to Nakayama Kentaro
    TI__Mastermind 19780 points

    Hi Kentaro,

    Nakayama Kentaro said:
    In this case, does it mean that the discharge resistor will be disabled when VCCA is lost, and the voltage of BUCK may not be 0V?

    Yes this would be the case if the load will not discharge the capacitors. Of course the capacitors will lose the charge slowly and when the PMIC would again get valid VCCA the pull-down resistors will be enabled and discharge the capacitors.

    regards,

    Niko

  • 0 in reply to Niko Alatalo
    Expert 1385 points

    Hello Niko,

    Thank you for your prompt reply.

    Kentaro