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TPS62177: Threshold of EN for delayed start

Robert Coulter
Prodigy 10 points
Part Number: TPS62177

The app notes and literature all have the EN pin connected to VIN. I would like to delay the ENable start up until VIN is greater than 9 volts. At what threshold and how much hysteresis does transition to EN on occur?

The sleep function has been troubling also and I don't know exactly when the sleep function is enabled by the MCU. There seems to be a race condition between 3.3 V to clock to disable SLEEP. The Sleep pin appears to me to be mis-labeled in that SLEEP is disabled when high and enabled when low.

  • 0
    TI__Expert 7320 points

    Hi Robert,

    It's ok to delay the EN signal after VIN, and you can find the threshold and hysteresis below in the datasheet.

    However, you should pay attention to the power sequence if you don't connect EN and VIN together. The voltage of EN should not be higher than VIN+0.3V during all the lifetime, which means the EN should be powered on later than VIN and be power off earlier than VIN.

    Robert Coulter said:
    There seems to be a race condition between 3.3 V to clock to disable SLEEP.

    I'm not sure where's the clock from. 

    The sleep mode can be simply understood as an GPIO function that you can enable the sleep mode by pulling low the SLEEP pin and disable the SLEEP mode by pulling high the SLEEP pin.