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TDC7201: TDC7201 measurement range in combined mode 2

Danlin Xiang
Prodigy 70 points
Part Number: TDC7201
Other Parts Discussed in Thread: MSP430F5529,

I have a follow up question regarding the answer in thread #3346975 below:

With combined operation, it supposed to have lower minimum measurement range than individual operation. So if the minimum range is reduced from 12ns in individua operation to 0.25ns with combined operation in mode 1, shouldn't the minimum range be reduce as well in mode 2? What the minimum measurement range can be achieved with combined Mode 2? 

Another related question. Is there any benefit of mixing mode 1 and mode 2 in combined operation than both in mode 2? ACAM has a reference design of mixing modes with two TDC chips for wide range laser ranging applications. Just wondering if the similar approach can be done on one TDC7201.

Thanks,

Danlin 

  • 0
    Prodigy 70 points

    Here is a link to the reference design of two TDC-GP22 in mixed mode for laser ranging.

    Thanks,

    Danlin

  • 0 in reply to Danlin Xiang
    TI__Expert 3450 points

    Hi Danlin,

    The TDC7201 combined operation is meant to be used in mode 1 only. The minimum ranges listed in the datasheet stand. 

    The device channels can be operated in modes 1 and 2 independently and simultaneously, so the TDC7201 should be able to perform similarly to the two GP22s used in section 4 "Wide-Range Application".

    Regards,

    Gabriel

  • 0 in reply to Gabriel Lake1
    Prodigy 70 points

    Thanks Gabriel.

    I doubt that the TDC7201 combined operation is meant to be used in mode 1 only. Otherwise how could it achieve the "Combined Operation: 0.25 ns to 8ms" as stated at very beginning of the datasheet. Also in the middle of page 5, note 4, it stated:

    (4) TDC7201 device in combined measurement mode where START1 and START2 are connected together:
    (a) A common REFERENCE_START signal is applied to START1 and START2 at least 12 ns before occurrence of actual START and
    STOP signals in Mode 1 (and at least 2 × tCLOCK before occurrence of actual Start and Stop signals in Mode 2).

    So based on the above statement from the datasheet, combined operation should be supported in mode 2. I am particular interested in the combined operation with one TDC in mode1 (for the true start signal) and other TDC in mode 2 (for the stop signal) to measure ToF in a few hundred micro-second. Could you get more info on this? Also do you have a reference source code to config the TDC7201 in combined operation?

    Thanks,

    Danlin

  • 0 in reply to Danlin Xiang
    TI__Expert 3450 points

    Danlin, 

    That is correct, sorry for the confusion. 

     To confirm, it sounds like you are asking about using TDC1 in mode 1 to record T1, and TDC2 in mode 2 to record T2? (see Figure 52 in the datasheet for reference). I think this should work fine, although we do not have test data with this specific configuration. Configure the TDCx, for mode 1 and mode 2 as needed. 

    The example source code we can provide comes with the TDC720xEVM GUI download available here. It will be in a directory called 'Firmware' once you unzip the GUI installation download. The firmware is written for the MSP430F5529 MCU, which is compatible with the TDC7201-ZAX-EVM. 

    Regards,

    Gabriel