Can TVS diodes interfere with I2C communication?

Question

I'm dealing with an application where our microcontroller is communicating with a slave device over I2C at 100 kHz fairly close to the MCU (less than 10 cm).

Everything works fine, but once we include TVS diodes on the lines communication with our slave fails with no acknowledge.

Vdd = 3.3 V, f = 100 kHz

These are the TVSs we've tried that have caused issues:

• RCLAMP0582BQTCT
• SR05.TCT

My thinking is that these are meant to protect high speed data lines and since we're only at 100 kHz, this causes problems. Am I correct in this?

UPDATE: Turns out it had nothing to do with the RCclamp. The slave device had an address change and we had no idea. Still very useful answers here.

^{simulate this circuit – Schematic created using CircuitLab}

Answer 1

If the bus is kept on one PCB, without exiting it, then the combined ESD input protection of the MCU and the slave devices will do the protection job. How have you determined that you even need the clamp?

The clamp will be somewhere along the I2C bus, so if the bus is long, the clamp will mostly protect itself, and the trace inductances will make it "invisible" at the chips that are connected to the bus.

If somehow you've figured out that you need this protection, then you'll need a clamp very near to each IC connected to the bus. And you'll want an ESD gun and a proper wideband, high-voltage scope probing setup to measure what's going on - otherwise it'll be merely a "feel good" measure without practical impact.

The clamp has parasitic capacitance lower than a x10 scope probe input. Probing the I2C lines with a scope probe will affect them more than the clamp's capacitance will. In other words: the clamp is transparent to I2C signals, at any frequency supported by typical I2C systems.