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TCAN1164-Q1: nRST state when VSUP goes down below UVSUPF threshould

Atsushi Hirai
Expert 3970 points
Part Number: TCAN1164-Q1

Hi team,

My customer want to know the behavior of nRST pin.

When VSUP goes down to slightly higher than UVvccoutf, VCCOUT hits UVvccoutf threshold and, nRST goes L due to Reset mode.

And if VSUP goes lower and hits UVSUPF threshold, the device goes to Power off mode.

In this case, does nRST keep L state in Power off mode?

If nRST goes to undefined state in low VSUP case, please tell me the voltage range of VSUP.

(my expected answer is for example "if VSUP is higher than 2V, nRST state is kept Low. If VSUP is lower than 2V, the nRST is undefined")

Best Regards,

  • +1
    TI__Guru 50555 points

    Hi Hirai-san,

    Your description and assumption are mostly correct here. While Vsup is falling, the nRST signal will go low when Vccout falls below UVccoutf. Once Vsup falls below UVsupf and the device moves to Power-off, this open-drain turns off. The pull-up to Vccout remains, but since Vccout is disabled, this will be a weak bias to an unpowered supply. With no external bias, the nRST state in the Power-off mode is essentially floating. 

    For your example, the value you're looking for is UVsupf. Once Vsup falls below this level, the nRST pin is essentially floating. 

    Let me know if you have any more questions.

    Regards,
    Eric Schott