K22 I2C0 pull downs crash I2C bus

[kevinlfw]

I'm working with the K22 and removed power from the chip, however kept I2C0_SDA and I2C0_CLK on PORTB connected to the I2C bus.  When I keep them connected while the chip is powered down, it pulls the entire I2C bus down.  When I remove the K22 from the bus, the bus operates as it should.  

What can I do, from the K22 side, to prevent this from happening, as I believe the pull-down is internal to the chip itself?

[mjbcswitzerland · Accepted solution]

Kevin

I think that a non-powered K22 will look like a diode to GND to the I2C bus (due to its passive GPIO protection circuitry). Probably you need to put MOSFET switches on the two lines and only switch them on when the K22 is powered.

Regards

Mark

[egoodii]

Exactly that cause -- I would go with a 'fully pre-designed' isolation concept like PCA9617A, or such from that family.