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TDC1000: Common Mode Timing

Omid (TI)
Intellectual 1470 points
Part Number: TDC1000

Hi Team,

 

Could you please assist my customer with the inquiry below. Thank you!

 

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For common mode, the 128 × T0 is too long and the 64 × T0 blank period is too short.  Is there any way to set the blank period to something in between?

 

  • 0
    TI__Mastermind 31655 points
    Hello,

    Could you please have the customer describe the expected timing in their system? How long between the START and the STOP, and where and how long would they like to blank the signal (a timing diagram would be very helpful)? Are they using Short TOF mode, or standard TOF mode? And what is their T0?

    The common-mode rise time is fixed, so I'm assuming the customer is referring only to the difference between the two settings of the Autozero period. Is that correct?

    Regards,
  • 0 in reply to Scott Cummins
    TI__Intellectual 1470 points

    Hi Scott, I think this picture sums it up.  You can see two large pulses, and then 14 muted pulses, and then some ringing.  After the ringing there's a first reflection off the bottom of our chamber, and then there's a very nice reflection at the top of the liquid.  Ideally we blank until just after the reflection off the bottom of our chamber.

    We're looking at the short time of flight blanking period.  Something between 64 and 128 would be perfect.  


  • 0 in reply to Omid (TI)
    TI__Mastermind 31655 points
    Hello,

    Unfortunately that is just the limitation of the settings. A way to get around this would be to change the clock input frequency. If you can use a higher frequency clock, you could get finer control over the blanking (with the tradeoff of shorter maximum blanking time) or you could possibly find a lower input clock frequency that puts one of these settings in the correct range for you. If the customer is using the TDC1000-TDC7200 they can easily test lower clock in frequencies by using the MSP430 internal clock instead of the 8Mhz oscillator.

    Regards,