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ADS8638: ADS8638 SPI communication problem

Younghan Lee
Prodigy 20 points
Part Number: ADS8638

HI!

I have an issue with ADS8638 thru SPI communication

Once I read the register, The IC can't send anything.

is there any problem with schematic or communication control?

Here I attached my schematic.

Thanks

  • 0
    TI__Mastermind 39115 points

    Hi Younghan,

    Your schematic looks good and actually pull-up resistors are not required on the SPI interface. Can you get correct conversion code from the ADC? Your timing plot for /CS,SCLK, DOUT and DIN captured with an oscilloscope will be very helpful to address the issue.

    Best regards,

    Dale

  • 0 in reply to Dale Li
    Prodigy 20 points

    Dear Dale.

    Thanks for your reply.

    In this case, I found strange things. 

    CS isn't going "HIGH" when disconnecting from HOST SPI.

    And I have a question about power voltage level.

    We draw a schematic with AVDD: +4V, DVDD: +3.3V HVDD: +11V, HVSS: -11V.

    Is there any problem using this voltage?

    Thanks.

  • 0 in reply to Younghan Lee
    TI__Mastermind 39115 points

    Hi Younghan,

    These power supplies are in the range of datasheet, however I would suggest you to use 5V for AVDD because the test condition for all specifications is 5V AVDD. 

     Can you get correct conversion code from the ADC instead of reading register? Need your timing plot to address the issue.

    Regards,

    Dale