While the resolution of the TDC7200 is listed as 55 ps the Measurement range for Mode1 is 12ns to 500ns I assume this means that the minimum time that can be measured between the start and stop signals is 12ns.
My intended use is not quite the same as the intended application but was hoping that I could use this part. I need to set the output on a microcontoller to high and measure the propagation delay through the circuit to the end point. For this I ideally need to measure the delay down to at least 2ns.
I can't immediately see from the datasheet why there is an apparent minimum of 12ns, the only thing I can assume is that there is a t-on delay of 6ns on the inputs making the minimum time to detect the stop and start times 12ns.
Would be grateful for any advice about how I might achieve my goal either using this part or point me in the direction of something more suitable.
My line of thinking at the moment is if I knew the exact time to turn on I could introduce a FET with the same t-on time as the input, this would mean that for example if the on time is 6ns I could connect my circuit under test in parallel with the TDC so that the high signal to the circuit would not start until the same time the TDC was ready to start counting. That still however leaves the turn off time, but I should therefore be able to compensate for that by deducting the off time from the measurements.
Basically...
(Start Trigger Signal) -> TDA7200 [START]
-> FET -> Circuit Near End -> Circuit Far End -> TDA7200 [STOP].
