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ADS1263 Conversion Speed Question

Daniel Vamos
Genius 3950 points
Other Parts Discussed in Thread: ADS1263

Hello Chris, Everyone,

I am using ADS1263 with pulse convert mode with speed 1200SPS. After every conversion the Differential Input channel is reconfigured. I would like know why the Conversion takes so much time: 1.267ms each time.

Another Question: In puse conversion mode the DRDY should go high as I issued the START command, but in my case it works different.

I have attached the saleae export. May I ask you to check it?

Thank you in advance,

BTW: I wish a happy new year! ;)Config.zip

  • 0
    TI__Guru** 113765 points

    Hi Daniel,

    Chris is currently out of the office.  The conversion times for the first conversion from the START condition is listed in Table 17 of the ADS1263 datasheet.  This conversion time includes startup and settling of the analog circuitry.  The timing begins at the last edge of SCLK following the START command and ends with DRDY going low.  I assume that channel 4 is DRDY, and when looking at this timing using the timing cursors I see 1.188ms which is the same as is shown in Table 17 for SINC1 filter at 1200sps.

    As far as DRDY is concerned, if DRDY is already in a high state DRDY will stay high until the conversion is complete.  As it does not appear that you are issuing the STOP command, you are running in continuous conversion mode when the data are read from the device setting DRDY high.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Genius 3950 points
    Dear Bob,

    Thank you for your reply. I am confused because I expected the conversion time less than 1000/1200 (~0.83ms) rather than 1.188ms. Forget about it.

    Regarding the STOP command, you are right. I am using RunMode: Pulse, but I do not send STOP command. Is it problem? In the datasheet 9.4.1.2. section says " further conversions are automatically stopped". So why should I send a STOP?

    Thank you for your answer.
  • 0 in reply to Daniel Vamos
    TI__Guru** 113765 points

    Hi Daniel,

    I realize that this can be confusing.  Notice that 9.4.1.2 is specifically referring to the START pin.  If you toggle the START pin, the device will convert once and then stop based on the state of the START pin.  If the START pin remains high (similar to issuing the START command) the device will enter continuous conversions.  When the START pin is taken high and then back low (or a pulse as in pulsed conversion mode) the device will start and take one conversion.  When using the commands you need to simulate the same behavior if you want only a single conversion by also issuing a STOP command.  The START command is like setting the START pin high, and STOP is like setting the START pin low. Refer to Figure 103 on page 61 of the ADS1263 datasheet.

    Best regards,

    Bob B 

  • 0 in reply to Bob Benjamin
    Genius 3950 points
    Thank you for the explanation. Btw, the START pin in tied to GND. Well I will update the code with STOP command as you request.

    Thank you for your time! Cheers
  • 0 in reply to Daniel Vamos
    TI__Guru** 113765 points

    Hi Daniel,

    Yes, START pin should be low if you use the START command for pulsed conversion.  Your current results are valid with your current code, it is just the nature of the DRDY that changes when adding the STOP command.  The STOP command should be issued prior to the end of conversion, or the next conversion will start.

    Best regards,

    Bob B