topic PCA9616 Max Capacitance on Differential Bus in Other NXP Products

PCA9616 Max Capacitance on Differential Bus

aswanton — Mon, 08 Sep 2025 20:34:29 GMT

Hello,

I am using PCA9616PW to communicate I2C between multiple boards on a backplane. Similar to this drawing but we use 3V3 for VDDA and VDDB

I want to add TVS diodes to the differential bus for protection, there is no mention in the datasheet about max bus capacitance. Is there a recommendation for maximum bus capacitance. I2C can be sensitive to too much bus capacitance due to the recessive state being passively pulled up. Is the differential bus similarly sensitive to bus capacitance?

My system can have up to 17 nodes and I am looking at a TVS diode with 50pF capacitance, would this be a concern?

Re: PCA9616 Max Capacitance on Differential Bus

guoweisun — Tue, 09 Sep 2025 06:00:52 GMT

There is no exact value but your can estimate it around above 1000pF.

Re: PCA9616 Max Capacitance on Differential Bus

aswanton — Tue, 09 Sep 2025 14:41:29 GMT

Thank you for the reply guoweisun.

I have estimated my single ended bus capacitance at 1185pF including TVS capacitance, trace capacitance and the IO capacitance of the PCA9616 itself. Which is over 1000pF but not very significantly.

Do you think this would be a concern?

Re: PCA9616 Max Capacitance on Differential Bus

guoweisun — Wed, 10 Sep 2025 02:37:41 GMT

I think it should be OK,you can test it and share with the result.

If it can't work you can go down the communication speed.