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TPS3842-Q1: Sense time delay and reset time delay are not expected according to datasheet

Max Chen1
Expert 1055 points

Part Number: TPS3842-Q1

Hi,

TPS3842A011DRLRQ1 for Voltage monitor,

image.png

 

measured Tcts = 123ms which is supposed to be 200ms - 371.5ms

measured Tctr = 260ms which is supposed to be 0.2ms - 0.3715ms according to datasheet

what possibly wnet wrong ?

Thanks

Max

 

  • 0
    TI__Genius 12830 points

    Hi Max, 

    Thanks for reaching out. Measured delays seems very long. What's the delay you are getting when CTS and CTR are open?

    To assist you better could you please share oscilloscope pictures that shows VDD, SENSE, and RESET? This way I can understand your inputs and the RESET behavior. 

    Where is TP357 is connected to? 

    Also if you looks at datasheet 8.2.2 Detailed Design Procedure, we do have a similar application use case. The device should be able to meet timing. 

    Best,

    Sila 

  • 0 in reply to Sila Atalar
    Expert 1055 points

    TP357 just local test point, it does not connect anywhere.

    when CTS is open, it is 16.8ms supposed to be 7us according to datasheet .

    see another ticket: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1618285/tps3842-q1-sense-delay-was-not-expected-according-to-datasheet?tisearch=e2e-sitesearch&keymatch=%20user%3A419570#

    sense delay

    reset delay

  • 0 in reply to Max Chen1
    TI__Genius 12830 points

    Hi Max, 

    Thanks for sharing the scope pictures. I also noticed the other E2E. I'll close that one, and support you here for both of the issues you mentioned.  

    1.How many TPS3842-Q1 units you have? And how many of them are showing this delay issue? 

    2.How many boards you have? Are they in production or a proto build? 

    3.Have you ever done ABBA swap test ? I recommend first testing with different IC, to see if a specific board is causing the issue. And once you confirm the issue follows the IC, could you please test them on another board? 

    This way we can understand whether the IC or the board is causing the delay. 

    Another option could be testing the units on TPS3842EVM. We can confirm if the units behaving as expected or not. 

    Best, 

    Sila 

  • 0 in reply to Sila Atalar
    Expert 1055 points

    2 ICs on each board, we have 2 total 2 boards, both of them have issues.

    we do not have EVM, I never thought we need EVM with this part though.

    has EVM have specific part :TPS3842A011DRLRQ1  ?

    I am afraid of only this programmable part has issue.

  • 0 in reply to Max Chen1
    TI__Genius 12830 points

    Hi Max, 

    This particular EVM configuration contains the TPS3842A011DRLR. (Non Q1 variant). From CTS and CTR delay behavior they should behave similarly to test. You can test the IC before putting it in your board. Measure CTS and CTR delay on the EVM first. And then solder it to your board, and again measure the CTS and CTR delay on your board. 

    EVM should be useful to identify what is the root cause. 

    Once you tested if you have still issues please let me know. 

    Hope this helps! 

    Best,

    Sila