• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 63 subscribers
  • Views 558 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS53355: If we connect the mode to Pgood, PGOOD to a external 3.3v or 5v with pull up resistor, whether it's ok

Frank Xiao
Genius 12055 points
Part Number: TPS53355

Hi team,

For the mode and PGOOD connection, If we connect the mode to Pgood, PGOOD to a external 3.3v or 5v with pull up resistor.

whether it has risks if we give the 3.3v or 5v after turn on the device? in my opinion, it fine.

whether it has risks if we give the 3.3v or 5v before turn on the device? what will happen if do this?

Thanks.

  • 0
    TI__Intellectual 2460 points
    Hi Frank,
    Please refer to section 7.4.1 on page 19 of datasheet on the Mode/PGOOD section. It needs to connect 3.3V or 5V so that I can read the SS, MODE section before the soft-start begin.
    Kit
  • 0 in reply to Henry Nguyen
    TI__Genius 12055 points

    Hi Kit,

    i have read the datasheet before. the PG is connected to external voltage supply 5v, for the sequence of the external 5v and input voltage, do we have some analysis？

    if the external voltage is earlier than input 12v, if the 3.3v is later than input 12v.

    What will happen?

    Thanks.

  • 0 in reply to Frank Xiao
    TI__Intellectual 2460 points

    Hi Frank,

    I am confusing with your questions. In the first post, you ask about the Mode pin connecting through PGOOD. Then, the IC needs to read MODE pin before the start up process.  After EN is high, the MODE through PGOOD needs to available for IC to read its resistance.

    In your second post, are you asking the PGOOD external pull up available before or after the input voltage?

    What is the delay between them? Will the PGOOD pull up available before or after the EN logic high?

    If MODE pin through PGOOD as in 1st post, PGOOD pull up voltage needs to available before EN high.

    Hope this help.

    Kit

  • 0 in reply to Henry Nguyen
    TI__Genius 12055 points

    Hi Kit,

    Thanks.  The question is if not connect the PG to Vreg， but connect to external 5v. Whether we have sequence  about the external 5v and Vin or EN. And why?

    In my opinion, give 5v later than 12v it should be fine.

    But if the 5V earlier than 12V and EN, I want to check whether it will influence the Soft start if do like this.

    Many thanks.

  • 0 in reply to Frank Xiao
    TI__Intellectual 2460 points
    Hi Frank,
    I understand that you want to connect PGOOD through external voltage pull up either 3.3V or 5V.
    It is ok to connect PGOOD to external voltage and nothing wrong with it. But, the external voltage needs to be available before the start up process since the MODE pin connecting through PGOOD as in your circuit. If the MODE pin connecting to GND for skip mode, then no need external pull up voltage available before start up since the can read the MODE pin as short to GND.
    Please re-read that section 7.4.1 on page 19. The first paragraph indicated that the IC needs to read MODE pin resistance to determine the soft start timing and mode of operation after soft start finished and PGOOD delay.
    Kit