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TDC7201: Unwanted stop signal within 10ns

Nam, Dino
Expert 5775 points
Part Number: TDC7201

Dear team, 

My customer consider using TDC7201. But they want to use under 10ns time between start to stop signal so we recommend combined measurement mode. 

If we use combined measurement mode, how can ignore unwanted stop signal within 10ns between 1st stop and 2nd stop signal?  Is it possible to detect 2 stop signal within 10ns?

At datasheet 6.3 Recommended Operation condition, Minimum time between 2 stop signals is 67ns.

And datasheet 7.3.3.3 Clock Counter STOP Mask, this part is also micro seconds time of flight example. 

Is it possible to ignore unwanted stop signal(unwanted reflection signal) if time between 2 stop signals is below 10ns? 

If yes, please share the guide. 

Thank you.  

  • 0
    TI__Mastermind 31655 points

    Hi Dino,

    You are correct that the clock counter stop mask is limited by the resolution of the input clock, and is on the order of 100s of nanoseconds. The workaround for this in combined mode is simply to increase the time between the Reference Start and when the actual LIDAR Start begins so that you achieve the correct stop masking.

    For example, if you wish to mask the first 10ns after the LIDAR signal begins and if you have an 8Mhz clock frequency, you can set the clock counter stop mask to 1, which would result in a masking period of 125ns. Subtract 10ns from 125ns to determine the time needed between the Reference Start and the LIDAR Start (T1). In this case that time would be 115ns.

    Unfortunately there is no way to detect multiple stop signals that arrive earlier than the 67ns spec you have mentioned above.

    Regards,