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DAC91001: Negative reference and supply for DAC91001

Tao
Prodigy 10 points
Part Number: DAC91001
Other Parts Discussed in Thread: OPA189

Hello,

I'm using a DAC91001 on my board for a 0-5V output span. Datasheet indicates that  REFNF should be tied to a 0V when used in unipolar output.

The way it's done in the reference design (presented in the datasheet, please see below) is through a buffer made from an OPA189 with in+ tied to GND. 

In the hope to simplify the (power rail) design. I'm wondering that:

1, can I simply tie the REFNF and REFNS to GND, omitting the buffer used here?

2. in this unipolar output config, can I use single supply for the OPA189 opamp? and

3. Can I use single supply on the DAC itself?

Thanks very much.

Tao 

  • 0
    TI__Mastermind 18546 points

    Hi,

    Please find my answers below.

    1. The design of the reference is done in such a way that both REFP and REFN should see the same impedance for better performance. That's one of the reason we recommend a buffered reference. So, yes buffer is required here.

    2. OPA189 is not input rail to rail, only output is rail to rail, So I dont recommend single supply(5V) for OPA189. If you can use above 7.5V ( input common mode range is (-V -100mV to +V -2.5V)), its ok.

    3. What do you mean by single supply for DAC? VSS to ground?

    Regards,

    AK

  • 0
    Prodigy 10 points

    Hi Akhilesh,

    Thanks for the clarification.

    Regarding Q3: Yes, I'm wondering if it can be powered by a single positive supply, with VSS to GND, given the unipolar output nature.

    Tao

  • 0 in reply to Tao
    TI__Mastermind 18546 points

    Hi,

    No we need min of -3V on AVSS even if device operates in unipolar mode. This is the requirement, otherwise device output will not swing to 0V. See the recommended operating conditions or VSS to GND ( -18V to -3V)

    Regards,

    AK