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Problem with PCA9306

Other Parts Discussed in Thread: PCA9306, UCD9081

In our design, PCA9306 is doing the I2C bus level shifting from +3.3V I2C bus to +1.8V I2C bus.

We want to use +3.3V I2C bus to talk UCD9081 to enable +1.8V power rail which is requried by PCA9306.

The problem is: before +1.8V is enabled, +3.3V I2C bus is dead because PCA9306 pull down +3.3V I2C bus to +2.2V.

We have pull up resistors on both +3.3V and +1.8V side.

Please let us know what is the problem for this.

Many thanks.

David.