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TPS54824: How to drive the EN pin of TPS54824 and Possibility of UVLO and Sequencing operation at same time

DEEPAK V14
Intellectual 810 points
Part Number: TPS54824

Hi,

Q1. Is it necessary to drive EN pin of TPS54824 with Open-Drain configuration or normal GPIO is enough?

Q2. I am planning to drive the 'EN pin' from a GPIO of uC/FPGA. The GPIO is not an Open-Drain pin. I can't ensure that this GPIO will be at Ground during initial Power-ON or during reset.GPIO may be at
       high impedance state during Power-ON or during reset. But I need to make sure the TPS54824 is not turned on when GPIO is at high impedance.Buck have to be turn-ON only when GPIO is at logic
       high(3.3V).

      To meet the above requirment, Do the configuration shown in attached image is sufficient?
      Jumper Position 2&3 :TPS54824 will enable by default with 12V input power having voltage dividor network
      Jumper Position 1&2 :TPS54824 will enable by according to the sequencing control from microcontroller(3.3V logic)


      

Q3. Is it possible to implement both UVLO fuction and Sequencing ON/OFF at the same time with EN pin ?

Thanks in Advance
DEEPAK V

  • 0
    TI__Guru**** 191445 points
    Hi Deepak,

    TPS54824 has an internal pull up on the EN pin. You have to actively pull EN low to disable the device. If the EN control is high-Z, the tpS54824 will turn on when the input voltage rises above the UVLO.
  • 0 in reply to JohnTucker
    Intellectual 810 points

    Hi John Tucker,

    Thank you for providing support on TPS54824.

    From your reply, I understand that floating the EN pin will enable the TPS54824 if the input voltage at VIN pin is rise above the threshold 4.1V typically.

    The EN pin threshold voltage to turn ON the device is 1.2V.

    My requirement is to make sure TPS54824 is not turned ON until the normal(not open drain) GPIO of uC/FPGA drive the EN pin to High voltage(3.3V).

    So for the normal operation jumper will be positioned at 1&2. Thus during every initial power ON even if GPIO of uC/FPGA is at High-impedance or ground, it will not turn ON the TPS54824 as the enable pin voltage is less than threshold voltage 1.2V.

    When GPIO is at High-impedance, the voltage at EN pin is around 99.6mV (=83K * 1.2uA). Thus TPS54824  is disabled.

    When GPIO is at Ground, the voltage at EN pin is around 1.2mV (=1K * 1.2uA). Thus TPS54824  is disabled.

    When GPIO is at High (ie 3.3V), the voltage at EN pin is around 3.3V (ie > threshold voltage 1.2). Thus TPS54824  is enabled.

    Q1. DO circuit attached to the previous post is sufficient to ensure proper Sequencing ON and Sequencing OFF control on TPS54824?

           Please give your suggestions.

    Thanks and regards
    DEEPAK V

  • 0 in reply to DEEPAK V14
    TI__Guru**** 191445 points
    Deepak,

    If read this correctly in the case of jumper 1 and 2 you will have the 1 uA pull up source and 83 kohm. 1 uA cannot pull that resistance up to the required EN voltage, so the device should remain disabled until the GPIO is set high.
  • 0 in reply to JohnTucker
    Intellectual 810 points
    Hi John Tucker,

    Thank you for resolving my queries. Now I am clear about controlling of TPS54824.
    Once again thank you for continuing support.

    Thanks and regards
    DEEPAK V