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TDC7201: Questions about the minimum wait time?

Kazuya Nakai59
Guru 21595 points
Part Number: TDC7201

Hello guys,

One of my customers is evaluating TDC7201 for their new products.

They have a few questions as the follows.

Could you please give me your reply?

They are evaluating TDC7201 with the following sequence.

[Sequence]

1. Set 0x81 to "TDCx_CONFIG1" register.

2. Input START signal.

3. input STOP signal.

4. Set 0x01 to "TDCx_INT_STATUS" register

5. Set 0x81 to "TDCx_CONFIG1" register.

6. Repeat from No.2.   

Their questions are the follows.

Q1. What is the time it takes to receive the START signal after a measurement starting ("START_MEAS" = 1)?

      (It is time between sequence 1 and 2.)

Q2. What is the time it takes to be possible a new measurement starting("START_MEAS" = 1) after writing "1" to "NEW_MEAS_INT" register. 

      (It is time between sequence 4 and 5.)

Q3. Is there any wait time as the minimum for each timing above?  

Your reply would be much appreciated.

Best regards,

Kazuya.

  • 0
    TI__Genius 14706 points

    Hello Kazuya, thank you for your question.

    1. There is no maximum time for receiving a start pulse after the START_MEAS has been set. The time between step 1 and step 2 is dependent on the external source used to generate the signal.
    2. I do not have any information on the time between the execution of step 4 and step 5. I can test this with an EVM, however it would not offer any guarantees for the timing of all TDC7201 devices.
    3. The datasheet does not detail the minimum wait time for the executing the listed steps. It is recommended to conduct system level testing to verify compatibility with the desired application. Minimum wait times are not specified due to the nature of different settings having influence over what the time may amount to (clock frequency, communication protocol, application). I can however comment of the minimum time between steps 2-3. For measurement mode 1, the minimum time between start and stop is 12ns, and mode 2 is 250ns.

    If you would like me to conduct any tests, please give me the details of the application to ensure my setup matches what you expect.

    Please let me know if you have any questions, or require assistance with understanding if the TDC7201 will be suitable in this particular design application.

    Thank you,

    Jacob

  • 0 in reply to Jacob Nogaj
    Guru 21595 points

    Hello Jacob,

    Thank you very much for your reply.

    Their application is a range sensor but they can't disclose a detail information about their product.

    They want to minimize the total time of the sequence .

    Also they found TDC7201 operated correctly when the time between step1 and 2 was 75ns.

    And when the time was 25ns, they found TDC7201 didn't operated correctly.

    They know that TI doesn't have the maximum wait time which can be guaranteed.

    But they want to know what is typical value is.

    They also want to know what typical value of the maximum wait time between step 4 and 5.

    Could you please check these typical values on EVM? 

    Thank you again and best regards,

    Kazuya.

      

  • 0 in reply to Kazuya Nakai59
    TI__Genius 14706 points

    Hello Kazuya, 

    Thank you for the information on the customer testing. I understand the customer wants to minimize the time to complete the sequence.

    Can you share the frequency used by SCLK? In some cases, the wait time is too small and the datasheet requirements for communication are violated.

    Once I know the SCLK frequency, I can recreate the customer sequence.

    Thank you,

    Jacob

  • 0 in reply to Jacob Nogaj
    Guru 21595 points

    Hello Jacob,

    Thank you very much for your strong supports.

    The customer uses 20MHz for SCLK.

    Could you please let me know if you need more information?

    Thank you again and best regards,

    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Genius 14706 points

    Hello Kazuya,

    Thank you for the additional information on the SCLK. In speaking with an expert on the TDC7201, they believe that the EVM will be incapable of accurately replicating the minimum wait time that the customer wishes to measure. This is because the EVM was designed to be used for general testing, not for fine timing evaluation. The expert suggested the best way to evaluate the TDC7201 is through measuring the device in the intended application. 

    Furthermore, it is difficult to accurately replicate testing conditions in lab due to the precise timing requirements. Small differences in setup could drastically change the data. 

    Is it possible for the customer to obtain the test data themselves? I am happy to review the data and offer suggestions if they would like.

    Thank you,

    Jacob

  • 0 in reply to Jacob Nogaj
    Guru 21595 points

    Hello Jacob,

    Thank you very much for your strong supports.

    I want you to review their test data because they are a important customer for me.

    What kind of test data or waveform are needed for your review?

    Are those SPI signal (DIN, SCLK, CSBx) and START1 signal waveforms?

    Thank you again and best regards,

    Kazuya.

      

  • 0 in reply to Kazuya Nakai59
    TI__Genius 14706 points

    Hello Kazuya,

    That is correct, Din, SCLK, CSBx, and START1 will be the most useful waveforms to probe.

    I would be interested to review the tests previously conducted. Step 1 – step 2 with 25ns between and 75ns between.

    I am also happy to look over any other waveforms the customer has questions over.

    Thank you,

    Jacob