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TPS53317A: Power management forum

Part Number: TPS53317A

hello

I am using the TPS53317A VR in a tracking configuration.

I have a digital Potentiometer that is connected between Vref pin and Refin pin and controls the voltage divider between those pins.

when I change the voltage in the Refin pin to approximately 2v the power good and the output drops to zero.
if I power the circuit in this condition (refin = 2v) than it works fine

if the change is to 1.9v (instead of 2v) - than it works fine in most cases (sometimes still fails)

what can cause this behavior?

  • Hi Gil 

    I'm not sure if potentiometer is playing something on VREF or REFIN when you change REFIN voltage to 2V. 

    If REFIN voltage is changed from a low voltage to 2V quickly, OC or output overshoot may happen and shut down rail. 

    Also, not sure the potentiometer bring noise to VREF and REFIN and cause problem. 

    Can you try a variable resistor and try again?

    Thanks

    Qian  

  • hi Qian

    thanks for the reply.

    just found how to attach a pic

    please see:

    green: refin

    blue:power good

    time per division; 20 micro-Sec

    as you can see it doesn't look as noise were inserted and the transaction is less than 10 micro-Sec.

    if during the transaction refin is above Vout, and output under-voltage protection makes shut down, than why immediately - by datasheet it should happen after 250 micro-Sec(section 7.3.5.4 in datasheet)?

    also. I tried to make the change small- from 1.9v to 2.0v and it still happening (but not 100% of times)

  • Hi Gil, 

    Can you probe Vref and Vout at the same time?

    Thanks

    Qian