PCA9306: Functionality Question

Abigail Leonardi

Part Number: PCA9306
Other Parts Discussed in Thread: SN74LVC2G66, TS5A23166, , LSF0002

Tool/software:

Hi,

My customer had a question about whether this device would suit their application. They are looking to do the following: isolate an active I2C bus from an inactive I2C bus - even when powered down there should be no voltage on one of the Vref pins. (Non powered bus may be floating - so it is not connected to a power supply device)

Is this possible for the device? If so, what Vref should be used for the active bus?

Thank you!

9 months ago

+1 Clemens Ladisch 9 months ago

Guru 316690 points

The two Vref pins are connected to each other with a MOSFET. The only way to isolate the two sides is by pulling EN low.

To isolate two buses, use a plain switch like the SN74LVC2G66. If the switch must also be powered down, use a switch with powered-off protection like the TS5A23166.

+1 Tyler Townsend 9 months ago

TI__Mastermind 47308 points

Hi Abigail,

I agree with Clemens here. Pull LOW on the EN pin of the PCA9306 to "isolate" the active bus from the inactive I2C bus.

Other options are the switches that Clemens mentioned.

Regards,

Tyler

0 Abigail Leonardi 9 months ago in reply to Clemens Ladisch

TI__Expert 3390 points

Wonderful, thank you! Do you have a recommended Vref for the active bus?

0 Clemens Ladisch 9 months ago in reply to Abigail Leonardi

Guru 316690 points

It does not really matter. Vref1 must not be higher than any pull-up voltage at the I/O pins. Vref2 must not be lower than Vref1.

When using the PCA9306 not for level translating but only as a switch, you can omit the 200 kΩ resistor, leave Vref1/2 open, and connect EN to the supply or GND. (And then you could just as well use the LSF0002.)

0 Tyler Townsend 9 months ago in reply to Abigail Leonardi

TI__Mastermind 47308 points

Hi Abigail,

I agree with Clemens here. Please let me know if you have any more questions.

Regards,

Tyler

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PCA9306: Functionality Question