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TPS3809-Q1: TPS3809K33DBVR will cause VDD to have a step when powering on

Alon Chen
Intellectual 370 points
Part Number: TPS3809-Q1

The performance of TPS3809K33DBVR in different production batches is inconsistent. If there is a problem, please help analyze the possible reasons. grateful. 

1. The problematic TPS3809K33DBVR will cause VDD to have a step when powering on. As shown in the figure below, the yellow bit is VDD and the green bit is RESET.


2. The picture below is from a normal production batch. 

  • 0
    TI__Mastermind 18690 points

    Hi Alon,

    Our team is looking into your inquiry, we will give you an update on Monday 5/20 PST.

    Jesse 

  • 0 in reply to Jesse Villanueva
    TI__Genius 9640 points

    Hi Alon, 

    Can you please quickly answer below question so I can better assist you on this inquiry? 

    - Did you test them on the same board? If not, can you please swap them and test to see if you still getting this unexpected behavior? 

    - Can you please provide more information what voltage the reset output is pulling up to and  how long you are experiencing the step behavior? 

    Best Regards,

    Sila Atalar 

  • 0 in reply to Sila Atalar
    Intellectual 370 points

    Hi Sila，

    1. I performed an AB-BA cross-test and this problem follows our TPS3809-Q1 chip
    2. the reset output is around 600mv and the step lasts around 180ms.

  • 0 in reply to Alon Chen
    TI__Genius 9640 points

    Hi Alon, Thanks for providing more information on this. 

    Is this behavior only happening at the start up?

    It seems like after some time later, both RESET and VDD goes up to 3.3V. Can you please test and let me know what happen at the RESET output if voltage at VDD pin goes below threshold voltage are you still seeing the step?

    TPS3809K33DBVR has typical threshold voltage 2.93V. If you look at the datasheet the maximum threshold can be 2.99V. 

    Is it okay if you can share a schematic that shows how are you connecting TPS3809-Q1? I know this is very simple design but just want to be sure we are not missing anything. 

    Best Regards,

    Sila