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TPS7A7100: Controlled by PCA9536

Part Number: TPS7A7100
Other Parts Discussed in Thread: PCA9536, PCA9557

I will controlled the output voltage of TPS7A7100 by i2c iio expander. Discribed in App Note:

I will switch between 1.2 and 1.8V.

So I have connect 100mV and 400mV of TPS7A71000 direct to ground. And 50mV, 1.6V leaved open. 200mV and 800mV connect to i2c IO expander.

If now I configure port P1 or P2 as input (high impedance), the output voltage is 0.0V instead of 1.0V

If P1 and P2 configure as output ('0'), the output voltage is 2V - correct.

if P1 is input and P2 is output, the Vout is 1V instead of 1.8V.

if P1 is output and P2 is input, the Vout is 0V instead of 1.2V.

What can be the problem?

Is the input impedance of PCA9536 not high enough? The app note is for PCA9557.