Other Parts Discussed in Thread: P82B96
Hi,
We notice a back-drive problem during hot-plug, if the I2C line connection is establish after 24V connection, but before 0V connection is made. The current made it back to main board 3V3 rail and kill the microcontroller. Path of the current is shown in red arrows in illustration below, through TVS and internal diodes of the I2C line buffer.
We are able to remove the current path via the TVS and microcontroller but not via the line buffer. We have the another part, P82B96 in hand and it does not have internal diodes and seems to solve the problem, but it fall out of our cost target.
Our product is one-time assembly by user so strictly speaking hot-swapping feature is not in the design requirement but I would like to improve the circuit robustness (while keeping cost low) in the event of user messed up the assembly sequence and plug in daughter board when main board is powered, while not using hot-plug connector and hot swap power supply.
Unless I test every single parts out there there is no way to tell if the part contain internal diodes. Is there a way to find out which other parts in TI's I2C buffer line-up that does no have internal diodes? Also, we can accept buffers with 400pF slave capacitance.
Regards,
SY
