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TPS53219A: Soft start adjustment

GARETH OU
Mastermind 8785 points
Part Number: TPS53219A

Hi 

Can you let me know

1-When the Mode Pin is connected to VREG (6.2V), is it possible to change the Soft-Start time with different resistance values?

2-If PGood (different pullup voltage 3.3V) can work normally? Can Soft-Start be adjusted according to Table 1 Forced CCM?

Is there documentation?

Thank you

  • 0
    TI__Mastermind 48180 points

     

    1) No.  The soft-start time selection uses the MODE pin resistance to ground during power-on-reset to determine the soft-start time.  If the MODE pin is tied directly to VREG, there is no measurable resistance to ground.

    Note: even if the MODE pin is tied to VREG, the TPS53219A will start-up in auto-skip mode as part of its pre-bias output voltage support.  Once it completes soft-start, the FCCM comparator on MODE is enabled.

    2) During Power-up and pin-detection, the PGOOD pin is forced to GND, so the pull-up voltage does not affect the MODE pin detection.  If the PGOOD pin is not pulled up above 2V, the MOSE pin may not be pulled high enough to exist auto-skip and enable forced continuous condition mode.

  • 0 in reply to Peter James Miller
    Mastermind 8785 points

    Hi Peter

    Thank you very much

    Pin#5 Mode is set according to Table1, but our POWER GOOD can only connect to 3.3V

  • 0 in reply to GARETH OU
    TI__Mastermind 48180 points

     

    Understood.  Using a Power Good pull-up to 3.3V is not a problem.  During Power One, when the MODE pin is detected, the pin will be internally pulled to AGND, so the TPS53219A will detect the resistance to PGOOD as a resistance to AGND.  Once the part is through soft-start and the PGOOD pin is no longer pulled low, the external pull-up to 3.3V will be sufficient to pull the MODE pin "High" and enable Forced Continuous Conduction Mode (FCCM)