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PCA9546A: Device Reset

Phil Salisbury
Prodigy 240 points
Part Number: PCA9546A


A few questions about reset:

  1. The data sheet 8.4.1 states "The /RESET input must be connected to VCC through a pull-up resistor".  I have a design where the /RESET line is driven from a TTL output from an MCU.  The MCU and PCA9546A are both powered from the same VCC = +3.3V.  The MCU powers up with outputs floating until firmware enables totem pole so the/RESET line is not pulled or driven until after VCC rises to 3.3V on powerup. What problems might result from this?
  2. The data sheet 8.4.2 states "Thereafter, VCC must be lowered below VPOR to reset the device".  Is asserting /RESET different than Power_On_Reset and how so?

Thanks

Phil

  • 0
    TI__Guru 74322 points

    Phil,

    An engineer has been assigned to this post and will reply after the weekend. Thank you for your patience.

    Regards,

    Eric Hackett 

  • +1
    TI__Genius 15345 points

    Hey Phil,

    1. The worst that could happen is your device is stuck in reset until your MCU drives the reset pin. Just ensure that you do not communicate with the device until the RESET pin is correctly driven.

    2.Yes, they both trigger the same reset circuitry. The power on reset will reset the device by controlling the VCC pin. Usually this happens automatically when you power the device off and on. The RESET pin will just require a toggle on the pin to actually reset the device. Both of these features preform the same function they just require different things to trigger a reset.

    Best,

    Chris