TCA6424A: I have a question about the reset timing requirements for the TCA6424A.

Hi User6448843,

tW = RESET pulse duration. This is the time needed to hold /RESET below a VCCP/2 voltage for a valid /RESET pulse. The width of the pulse needs to be at least 4 ns in length for it to be considered a valid /RESET pulse. Anything faster than this, and the reset condition may not be recognized by the I/O expander. 

tREC = RESET recovery time. After a successful reset condition is given (high-low-high on /RESET pin), there exists some time before an I2C start condition can be issued. In this case, the tREC = 0 ns, so after a reset condition, a start condition can immediately occur. 

tRESET = Time to RESET. In the graph, the example is if SDA is held LOW or an I/O (Pn) is held LOW/HIGH, at what time will the I/O expander reset back to its default state. On the falling edge of /RESET being toggled, you need at least 600 ns of time to see Pn or SDA go back to their initial conditions. 

Please let me know if you have any additional questions.

Regards,

Tyler