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RESET_IN pin of TPS659037

Michi Yama
Guru 10030 points
Other Parts Discussed in Thread: TPS659037, AM5728

Hi,

I have some questions regarding RESET_IN pin of TPS659037.

My customer uses TPS659037 PMIC with AM5728. And they use RESET_IN pin as PMIC ON/OFF control.

At present. on customer's board,  overshoot/undershoot of input signal to RESET_IN is bigger than spec.

Please see the below picture.

As you see from the above picture, the overshoot voltage is less than 5.25V(Input Votage maximum). This is no problem, I think.

However, the undershoot voltage is less than -0.3V(VIL min.).  But time of the undershoot is approximately 6ns. It is very short.

I think this is no problem if the spec of VIL min. is for protecting of the internal diode's continuity.

Customer's question is the below.

1. Are there problems the above overshoot / undershoot?

2. If there are problems, please let me know the expected troubles. Especially customer would like to know regarding undershoot.

I appreciate your quick reply.

Best regards,

Michi

  • 0
    TI__Genius 16410 points
    Hello Michi,

    The overshoot is not a problem, since the device supports up to 5.25V on RESET_IN.

    The undershoot does violate absolute max, so it may be a risk to the device. Although it's a short period of time, there is risk to damage the device when the input drops below -0.3V. I suggest to smooth out the signal, so it does not go below -0.3V.

    Regards,
    Karl
  • 0 in reply to Karl Wallinger
    Guru 10030 points
    Dear Karl-san,

    Thank you for your support.

    Regarding the undershoot, customer would like to know detailed information "damage the device". What part of the device may be damaged? And how damage is expected by undershoot?

    I appreciate your quick reply.

    Best regards,
    Michi
  • 0 in reply to Michi Yama
    TI__Genius 16410 points
    Hello Michi,

    The device has an ESD diode on this pin, and the risk is damaging this diode by pulling the input too low and conducting too much current through the diode.

    Actually, if the customer can keep this ringing event to <20ns, they shouldn't see any damage. But the risk increases the longer the RESET_IN pin is held below -0.3V.

    Regards,
    Karl