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PCA9306: PCA9306 unpowered behaviour

Rafael Silva1
Prodigy 20 points
Part Number: PCA9306

Greetings,

I am working on a low power application in which i have an MCU at 3.3V and a device (an MPU)  at 1.8V, i am looking to use the PCA9306 for level translation of the I2C between these devices.
Since this is a low power application i want to be able to turn the device off and so i have the 1.8V regulator enable conected to the MCU, this means that the PCA9306 will have VREF2 at 3.3V and VREF1 at GND.
Here is my circuit with the 1.8V enabled:


And here the equivalent circuit when the 1.8V regulator is disabled:


My questions are:

What behaviour will the PCA9306 have with VREF1 @ GND, will it pull the 3.3V side Low?

With VREF1 @ GND and EN @ GND , will it pull the 3.3V side Low?

Will this damage the PCA9306 over short or long term?

  • 0
    TI__Guru 62920 points
    Hi Rafael,

    We are looking into this and will get back to you later today.

    Max
  • 0 in reply to Miguel Robertson
    TI__Guru 71790 points
    Hey Rafael,

    Very sorry for the delay, I'll get back to you by the end of the day.

    Thanks,
    -Bobby
  • 0
    TI__Guru 71790 points

    Hey Rafael,

    "What behaviour will the PCA9306 have with VREF1 @ GND, will it pull the 3.3V side Low?"

    The device will technically be disabled however this may actually defeat the purpose of what you are trying to do, as it will actually increase the bias current through the PCA9306. I estimate your bias current to PCA9306 would then be around 13.5uA. (3.3V-0.6V)/200k. If this uses more than it saves, then I would recommend removing the 200k pull up resistor and GND the enable pin of PCA9306

    "With VREF1 @ GND and EN @ GND , will it pull the 3.3V side Low?"

    No, Just plugged my PCA9306 and set Vref1 to GND with Vcc2 powered up (enable sees 600mV like I expect) and SCL remains at 3.3V. You can see this below, where purple is SCL and green is the enable pin.

    "Will this damage the PCA9306 over short or long term?"

    No damage.

    Thanks,

    -Bobby

  • 0 in reply to BOBBY
    Prodigy 20 points

    Than you very much for your help, i have what i need.

    Regards,

    Rafael Silva