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DAC8871 VREFL with a Single Supply

Dave Boechler
Prodigy 70 points
Other Parts Discussed in Thread: REF5010, DAC8871

I am trying to determine the best way to terminate VREFL-F and VREFL-S in a single supply environment. I believe I have VREFH-F and VREFH-S covered for a REF5010 voltage reference on the high side reviewing documents SLAU233, SBAS396A and SLAA371

What is the correct way to do this?

Do I still need an Op Amp or can VREFL-F tied to VREFL-S and decoupled to Analog Ground?

Thanks 

  • 0
    TI__Genius 10615 points

    Hello Dave,

     

    Using a buffer for both VREFH is recommended because the reference is subject to different loading depending on the output voltage of the DAC. The RC filter is in place in order to reduce the noise introduced by the reference, because the noise introduced by the reference will propagate through the DAC to the output.

    I need to double check why we recommend a capacitor between the Force and Sense lines, but I suspect it is to compensate for any stability problems that the low-pass filter can cause by being inside of the amplifier loop.

    Dave Boechler said:
    Do I still need an Op Amp or can VREFL-F tied to VREFL-S and decoupled to Analog Ground?

    When you say that you are in a single supply environment, I'm assuming that VREFL will be GND. If this is the case, a buffer is not recommended. You can tie VREFL-F and VREFL-S directly to GND.

  • 0 in reply to Eugenio Mejia
    Prodigy 70 points

    Hi Eugenio 

    You are correct. The VREFL-F and VREFL-S with be tied to GND (Analog GND). So I will move ahead based on your guidance.

    On the issue of decoupling capacitors between the Force and Sense line. SBAS396A (DAC8871 Datasheet) on page 16 has them. The other two reference documents for the DAC8871 do not. Clarification would help.

    Thanks