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PCA9517: Power OFF Sequence / OE Sequence requirements

Shimizu Kensuke
Prodigy 80 points
Part Number: PCA9517


I have two questions about the PCA9517.
(1) Do you have any requirements regarding "the power off sequence"?
(2) Do you have any requirements regarding "the timing of power and EN"?

  • +1
    TI__Guru 53278 points

    Hello Kensuke,

    Shimizu Kensuke said:
    (1) Do you have any requirements regarding "the power off sequence"?

    PCA9517 has built in powered-off high impedance I2C pins. This means that when VCCB and/or VCCA = 0V, all inputs and I/Os are over-voltage tolerant up to 5.5V. 

    Shimizu Kensuke said:
    (2) Do you have any requirements regarding "the timing of power and EN"?

    The EN pin is an active-high enable with an internal pullup to VCCB. Upon powering VCCB, automatically powers up EN to be set HIGH. It is highly recommended not to change the state of the EN when communicating otherwise the bus could hang up. Only change EN when the I2C bus is in an idle state. 

    There is no order of powering up required for the EN pin when powering VCCA or VCCB. VCCA or VCCB can be applied in any sequence at power up. An internal power-up circuit keeps the output drivers turned off until VCCB is above 2.5V and VCCA is above 0.8V.

    Regards,

    Tyler