PCA9306: Another I2C master device on PCA9306 on side #2

Kazuhiko Hirano said:

Part Number: PCA9306

Hello,

 

My customer is using PCA9306 as follows.

In normal operation, I2C master device (1.8V) communicate with I2C slave device (3.3V) via PCA9306.

During debug, the I2C master device is power down (1.8V power supply is off), and other I2C master devices for debugging purpose (3.3V) communicate with the I2C slave device directly.

 

Q1:

During debugging, 1.8V is off and 3.3V is on at PCA9306. Could this damage TPA9306? Or is this OK with no issue?

[Bobby]

This wouldn't damage our device but you may see leakage current into side 1 from Vref2 thoough Vref1. If the leakage current has no where to go, it may build up and find a path through an ESD diode of a device on that 1.8V rail. You can place a weak pull down resistor if this is something you see happening.

 

Q2:

During debugging, PCA9306 is still connected with 3.3V is on. The I2C master devices can communicate with the I2C slave devices with no issue?

[Bobby]

No issues I can think of, if you really want to though you can connect/short the enable pin to GND during this debug testing.

Best regards,

K.Hirano

Comments above in BOLD.

-Bobby