Different voltage levels damaging USB-8451?

[LarryC-ATS]

We just started using I2C communications in our product so I am not very familiar with it.  We are using the USB-8451 to communicate with a HCS08 device. The SDA and SCL lines are pulled up to 3.3V on the unit under test with 5.11K. The NI USB-8451 appears to be damaged if the +5V and the +3.3V from the UUT are shorted. The +5V from the USB-8451 is not used. The manufacturing issues have been addressed. We want to keep the device from harm if this mistake happens again.  

We are not seeing any reason the different voltage level should affect the 8451, but we have a dead device. Any ideas on how this is happening or how to mitigate this in the future?

Thanks, 

Larry

[Jeff.St]

Hi Larry,

There is information on how to wire the USB-8451 without damaging it on page 3-10 of this manual.  Also take a look at the specifications section in Appendix A.

Best,