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PCF8575C: Issue regarding the open drain outputs pulled to VCC

Nanje Gowda H N
Prodigy 60 points

Part Number: PCF8575C
Other Parts Discussed in Thread: TCAL6416

I am using the PCF8575C GPIOs as open-drain outputs. The IC VCC rail and the external pull-up resistor rail are from different 3.3V power domains. Although both rails are at the same voltage level, they may not power up simultaneously and there could be some startup delay between them. Could you please confirm whether this condition is safe for the device, especially when the GPIO pins are pulled HIGH while VCC is still OFF, and whether there is any risk of back-powering or latch-up?
If there is any issue can u suggest any other alternate ic which will support above requirement.

 

  • 0
    TI__Guru 64988 points

    Hi Nanje,

    This device does not seem to implement true voltage tolerant IO's. If VCC = 0V, and 3.3V is applied to the I/O's I assume this case is not supported by the device. 

    Can you consider using a device like TCAL6416 that has dual power supply rails? 

    Regards,

    Tyler