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8 bit DAC with Internal Reference

460822
Genius 4055 points

Other Parts Discussed in Thread: DAC5311, TLV5624, DAC081S101

I need an 8 bit DAC with an internal voltage reference ... powered by 3v ... output ranging from 0 to 2v ... SPI communication.

The DAC5311 has no internal voltage reference ... uses the power rail ... which can change over temperature.

The TLV5624 has an internal reference, but has a max output of 1v with a 3v supply.

Any suggestions?

  • 0
    TI__Mastermind 23235 points

    Mr Eisenbeis -

    TLV5624 might be an option.  Otherwise, the DAC5311 (which you noted) is your other option 8-bit DACs with using REF as VDD.  Keep in mind, you still need a fairly clean power-supply for the DAC power.

  • 0 in reply to Greg Hupp
    Genius 4055 points

    I should have been more clear.  I'm looking for a third choice. 

  • 0 in reply to 460822
    TI__Mastermind 23235 points

    TLV5624 should get your requirements, unless there is something else that you didn't mention.  Check out Fig 2 and output voltage equation on page 10 - output is ~2 x vref.

  • 0 in reply to Greg Hupp
    TI__Expert 6925 points

    Hello Clyde,

    Do you need the voltage from the REF pin somewhere else in your board? If not, then you should be able to use the TLV5624 just as Greg recommends.

    Although the TLV5624 can only provide a 1.024V voltage at the REF pin when using a 3V supply, the OUT pin has a gain of 2, and it can go up to 2.04V.

    Its transfer function is:
    OUT = 2 * REF * Code / 256
    OUT(max) = 2* 1.024V * 255 / 256 = 2.04V

    Best regards,
    Rafael

  • 0 in reply to Rafael Ordonez
    TI__Genius 12705 points

    Clyde,

    Another couple of options:

    1) Drive the DAC5311 with an acceptable external reference (2.048V) 'as the Vdd supply'.

    2) Buffer the TLV5624 REF pin for the REF value you need for the rest of you circuit. The TLV5624 already can put out 2V as cited above.

    We have some nice 'zero offset' amplifiers that can easily do this.

    Mark Pearson

  • 0 in reply to 460822
    TI__Guru**** 182701 points

    Hi Clyde,

    A third choice might be the DAC081S101.  Like the DAC5311, the reference is derived from the analog voltage rail.

  • 0 in reply to Tom Hendrick
    Genius 4055 points

    TLV5624 data sheet, page 5 ... the reference max is Vdd - 1.5v.  With Vdd of 3v, the max is 1.5v. 

    Using the voltage rail is a problem over temperature ... -40 to +85 deg C.  The voltage rail will quite like change over temperature ... not a good way to obtain an accurate DAC output. 

    It's puzzling TI does not provide a DAC controlled by a voltage reference (internal or external).

  • 0 in reply to 460822
    TI__Genius 12705 points

    Hi Clyde,

    Do you know what kind of tolerance your power rail has over temp?

    The TLV5624 does have an internal VREF (1.024V @ 3V power rail). But i believe you want a higher Vout Max from the DAC. (how high?)

    You could take and drive a DAC101S101with a REF3030 (3V output reference) from a 3.3V rail... I'll send you what that would look like in an email.

    Mark P