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BQ40Z80: About BQ40Z80 using the Pres pin function

zhang jianhang
Prodigy 130 points
Part Number: BQ40Z80

HI TI experts：

        I have encountered a problem when using the Pres pin function of BQ40Z80, and I need your help.

        When I did not use the Pres pin as a key switch, it was no problem to hit ESD after connecting 10K to ground.But after I use the Pres pin as a key switch, the ESD that touches 4K and air 8K cannot pass.It seems that this Pres pin is very sensitive, causing the ESD test to fail. Do you have any good suggestions? Looking forward for your reply, thank you.

  • 0
    TI__Guru** 102355 points

    Hello Zhang,

    Using a TVS diode and capacity like you have on your schematic should be sufficient. Can you clarify what you mean with connecting 10K to ground? and 4K and air?

    What is failing on the gauge, what are the signs you are seeing?

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 130 points

    Hi Wyatt，

         Thank you for your answer.

    4K contact and 8K air or 8K contact and 15K air are our standards for testing ESD.
    When I did not use the Pres pin as a button, connect the Pres to 10K to GND. At this time, the ESD test can pass.
    After I added the Prse pin as a button function, I used a 5.6V Zener tube and a C102 capacitor as shown in the figure above, but it failed the ESD test. After the test, the fuel gauge could not communicate and work directly.
    Can you tell me how to choose TVS tube? Or is it affected by my other circuits?

  • 0 in reply to zhang jianhang
    TI__Guru** 102355 points

    Hello Zhang,

    You should use a TVS diode that prevents the maximum voltage from appearing on the pin to prevent ESD damage. There are many option for TVS diodes, but I would recommend going with a faster diode if you are getting ESD damage to the pin.

    Sincerely,

    Wyatt Keller