• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 30 subscribers
  • Views 181 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TDC7200: Calculation of system accuracy

ANDREW DEMEDEIROS
Prodigy 80 points
Part Number: TDC7200

Tool/software:

Hi,

I have a system which uses the TDC7200 to determine the time interval between two input pulses. The system works well, however I am having difficulty trying to determine what the accuracy of my system is. My pulse length typically in the 100uS to 500uS range. My system is setup in Mode 2, using a 16MHz oscillator. The oscillator is a ECS-TXO-2016-33-160-TR, which has a maximum stability tolerance of +/-2.5ppm.

In the clock accuracy section of the datasheet (section 9.4.1),  accuracy/error of the system will be the measured time x the stability tolerance. In my situation, the worst error would be 500uS * 5ppm/1E6, or 2.5nS. However this doesn't take any of the TDC7200 errors into account?

Any thoughts as to how I could obtain a full picture of the total error in the system?

Thank you!

Andrew

  • 0
    TI__Genius 13900 points

    Hi Andrew,

    Thank you for posting to the Sensors forum!

    ANDREW DEMEDEIROS said:
    However this doesn't take any of the TDC7200 errors into account?

    Do you have any specific errors that you would like to account for in mind? Section 9.4.2 also has an equation showing how to calculate clock jitter.

    Best,

    ~Alicia

  • 0 in reply to Alicia Rosenberger
    Prodigy 80 points

    Hi Alicia,

    I had seen the section on jitter as well. Ask of that relates to external sources of error. I'm trying to determine the error related to the tdc7200 itself. Am I thinking about this incorrectly? 

    Thanks! 

    Andrew

  • 0 in reply to ANDREW DEMEDEIROS
    TI__Genius 13900 points

    Hi Andrew,

    I'll need some time to look into this and will get back to you on Monday.

    Best,

    ~Alicia

  • 0 in reply to Alicia Rosenberger
    TI__Genius 13900 points

    Hello Andrew,

    We do provide a spec for accuracy on the datasheet for mode 2, I have included a snippet below:

    Also note that the TDC7200 provides calibration results that measures the offset between the internal oscillator and the external clock source for the smaller ring oscillator measurements. This essentially allows the user to reduce the timing errors that are introduced due to the internal timing differences of the TDC7200, the main concern should be the external clock since this is still the reference clock for the timer and too much deviation or jitter on this clock would increase the errors observed on the internal timer.

    Best,

    ~Alicia