TDC7200: Minimum time between START and STOP signal: <10 ns

Casey,

I'm not aware of another conditioner like TDC7200 with a shorter delay between the start and stop.  What range are you attempting to detect?  Assuming an air coupled transducer, a delay of 12 ns between start and stop would equate to a round trip distance of about 2 um.  A challenge you will find in any system at this kind of range will be that at short distnaces, the echo will return before the transducer has stopped it's ringdown.  As a result, it is likely easiest then to use the device in a bistatic configuration where transmit and receive are handled through separate transducers.

Thanks,

Scott  

Hi Scott. Thanks for the reply.

I'm trying to time the delay between two rising edges of a single-ended LVCMOS signal. The expected delay will be on the order of 13 ns, but there may be some applications where it could be shorter (~6 ns), so I am concerned the TDC7200 wouldn't be able to measure the delay given its T1_{STARTSTOP_Min} requirement (>12 ns). It seems like an odd spec to me, given that the resolution is ~55 ps. I guess there is some kind of "setup" or "initialization" happening on the rising edge of START which means the TDC2700 will not be "ready" to capture the STOP pulse for at least 12 ns.

Hey Casey,

We have seen the TDC7200 operate at less than the 12ns at room temperature but not as low as what you would require for your application. You are certainly correct that there is a sort of  "setup" that the device undergoes before measurement which prevents it from performing even smaller measurements. Since this device is geared towards time of flight measurements for ultrasonic or lidar typically for those applications the 12ns timing requirement works fine.

Another idea might be if you could add a known delay between each LVCMOS signal in order to get above the 12ns threshold, you then could just subtract the known delay from your measurement result in order to obtain the real time measurement between the two rising edges.

On another note it might be useful to make a generic post on the clock and timing forum, it is possible they might be able to recommend a device that meets the timing requirements for you application.

Best,

Isaac