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DAC7571: When VDD is 0V, SDA & SCL voltage level goes around 2.2V

Part Number: DAC7571

Hi,

This is my block diagram and has one issue.

When VDD2 is 3.3V, I2C operation is normal.

But, when VDD2 is 0V, SCL & SDA level of DAC7571 go down around 2.2V and I2C operation is abnormal.

As I know, I2C is BUS. So, SCL & SDA level should be 3.3V regardless VDD2 voltage.

When I remove DAC7571, SCL & SDA level is 3.3V and I2C operation is normal also.

Is there anybody who help me?

Thanks in advance.

Kevin