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TPS3435-Q1: Need output high with open drain output version at no power supply

Will Wang47
Expert 6030 points
Part Number: TPS3435-Q1

Hi team,

Customer get an application using TPS3435-Q1 open drain version.

Their TPS3435-Q1 power supply is different with the pull up voltage.

They get one requirement, the pull up voltage is always on; and they pull down the supply voltage to GND, mean no supply voltage to TPS3435-Q1.

During this case, they still want to TPS3435-Q1 WDO keep pull-high. 

However, during their test, they find the WDO get pulled down.

Could you help check why this happen and how could they achieve get WDO high without power supply?

Thanks and Best Regards,

Will

  • 0
    TI__Expert 4350 points

    Hi Will, 

    Thanks for your question. Since there is no supply voltage you are not powering the device, and if you look at the  device functional modes in section 8.4 you'll see that if VDD less than VPOR, WDO output is undefined. 

    I checked with my team and VPOR is 0.9V  for open drain output version. After Vpor, they can keep watchdog disabled until the device boost up.  

    I hope this helps!

    Best Regards,

    Sila Atalar