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TDC7201: Minimum TOF distance

Art Mecina
Genius 16655 points
Part Number: TDC7201

Hello Guys,

Good day!

I just want to confirm if the TDC7201 can be accurate down to 1cm TOF?

Because datasheet only mentions that the TDC7201 is suitable to applications ranging from 0.25 ns to 8 ms which translates to 3.755cm to 1200km I think. 

Thanks for the clarification!

Art

  • 0
    TI__Mastermind 27950 points

    Hi Art,

    The TDC7201's minimum time of flight value in the combined operation mode is 0.25ns, and maximum in either individual mode 2 or combined mode is 8ms. Assuming you asking with regard to LIDAR/optical (where speed of light is 3*10^8 m/s), then yes, the round trip time of flight is converted to distance using d=v*t /2 for a range of 3.75cm to 1.2km.

  • 0 in reply to Akeem Whitehead
    TI__Genius 16655 points

    Hi Akeem,

    Getting back on this. The confusion came from the Section 8.2 of the datasheet shown on the attached image where 1cm accuracy was given. Can you confirm if device is indeed capable of 1cm measurement?

    Thanks in advance!

    Art

  • 0 in reply to Art Mecina
    TI__Mastermind 27950 points

    Art,

    The highlighted sentence refers to step resolution (accuracy), not minimum range. The TDC7201 has a step resolution of 55ps (rounded up to 67ps is 1cm in distance), meaning if the minimum distance that can be captured is 3.75cm, the subsequent distances that can be captured are 4.75cm, 5.75cm, ... etc. 

  • 0 in reply to Akeem Whitehead
    TI__Genius 16655 points

    Hello Akeem,

    Thank you for the clarification.

    I hope i am not being repetitive, but our customer wanted to know the accuracy of each measurement even though i have already provided the information above. Do we have such information or other info that can be provided?

    Thanks!

    Art

  • 0 in reply to Art Mecina
    TI__Mastermind 27950 points

    Hi Art,

    The TDC720x has a single shot resolution of 55ps, an accuracy (defined as the systematic error in the output signal; the error of the device excluding noise) of 28ps, and the standard deviation is 35 or 50ps depending on the measured time (1 and 100 us respectively). See table 6.5 on page 6 of the TDC7201 datasheet for these TYP specifications.

    Note: as the reference clock frequency is increased, the standard deviation (or measurement uncertainty) reduces. Therefore, using a reference clock of 16 MHz is recommended for optimal performance. See Figure 20 in datasheet for Standard Deviation vs CLOCK comparison.