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PCA9306: Can the sides be used interchangeably

Mark Baum
Prodigy 155 points

Part Number: PCA9306

Hello,

I need some advice on something that is almost a silly question to ask.

The data sheet on the PCA9306 refers only to the master being on the VREF1 side and the slave on the VREF2 side.

However, because the master is 3.3v and can go as high as 4.6v and the slave is 1.8v exact, I feel it would be best to let VREF1 handle the slave and VREF2 handle the master.

Is there any concern in doing this? - nothing I see implies there is, but just checking in case..

The ONLY thing I could see is that VREF2 requires a 200Kohm resistor which controls the current draw of the device, however in my intended application (having the slave on the other side) would the current draw be limited properly as well?

Thanks in advance for your help!

Regards,
Mark

  • 0
    TI__Guru* 80511 points
    Hey Mark,

    "The data sheet on the PCA9306 refers only to the master being on the VREF1 side and the slave on the VREF2 side"

    -PCA9306 is a bidirectional level translator which means it does not care which side the master is on. You can place master on side 1 or side 2, it does not matter.

    "The ONLY thing I could see is that VREF2 requires a 200Kohm resistor which controls the current draw of the device, however in my intended application (having the slave on the other side) would the current draw be limited properly as well?"

    -This resistor is actually there to limit current flow from Vref2 to Vref1 while in the recommended set up, this set up is used to establish a reference voltage which the device uses in other areas in the device for better performance. As long as you have the 200k ohm resistor set up properly, the device will not be damaged (wrong set up may damage the device). To be more direct here, this current does not flow into SCL or SDA it will not affect your slave/master in that sense.

    So yes, from what I understand your set up should not run into issues as long as the device is set up properly (EN pin and Vref2 tied together with a 200k pull up to Vcc2).

    Thanks,
    -Bobby
  • 0 in reply to BOBBY
    Prodigy 155 points

    Brilliant - thank you very much.

    I was 99% there, but your confirmation makes it 100%

    Take care,
    Mark