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DAC70501: Reference divider and buffer gain

Shiga Yuichi
Prodigy 80 points
Part Number: DAC70501

When the reference input voltage is 5V and  VDD is also 5V, Do I have to set the REF-DIV to 1(the reference voltage is internally divided by a factor of 2) and also set the BUFF-GAIN to 1(the buffer amplifier for corresponding DAC has a gain of 2.)?

I sent the following data via SPI, and input the 5V as reference voltage. But DAC did not work and output voltage was always 0V.

  • Set the Config Register to 0000_0001_0000_0000
          ->disables the device internal reference
  • Set the Gain Register to 0000_0000_0000_0000
          ->the reference voltage is unaffected
          ->the buffer amplifier for corresponding DAC has a gain of 1

What is causing this problem?　Is this setting a violation? or improper configuration that triggers a reference alarm condition?


If I have to set the REF-DIV to 1 and also set the BUFF-GAIN to 1. Can I get the  following specifications.

  • the error of reference divider
  • the error of gain of the buffer amplifier (gain is 2)

  • +1
    TI__Mastermind 41313 points

    Hi Yuichi-san,

    Yes, with a VDD of 5V, the reference input needs to be between 1.2V to 2.5V with the REF-DIV bit set to 0, or 2.4V to 5V with the REF-DIV bit set to 1:

    The reference buffer is shut down if the above conditions are not met. 

    You would need to set the BUFF-GAIN bit to 1 (gain of 2) to achieve the 0 to 5V output range. The max error specs for the DAC70501 in the datasheet include the errors when the REF-DIV and BUFF-GAIN bits are set to 1. We don't have data for the individual contributions of the reference divider and buffer as we don't have a way to determine those errors independently. 

    Best,

    Katlynne Jones

  • 0 in reply to Katlynne Jones
    Prodigy 80 points

    Dear Katlynne

    Thanks for your information. I understood that I need to set the REF-DIV bit to 1 and BUFF-GAIN bit to 1.

    There is no problem if the datasheet include these error as you mentioned.

     

    You are a big help always, and I appreciate your support.

  • 0 in reply to Shiga Yuichi
    TI__Mastermind 41313 points

    Hi Yuichi-san,

    You are welcome. Please let me know if you need any additional support.

    Best,

    Katlynne Jones