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External Reference circuits for two or more DACs

JACR
Intellectual 270 points
Other Parts Discussed in Thread: DAC8871

 

Hi people

 

I have been using the DAC8871 for quite some time now and i think its the perfect choice when you want positive and negative signals (and also if you need more than one generation range).

 

Now, i am thinking about using several DAC8871 in a multichannel application and im not quite sure how to adress the topic of the reference voltage and  force and sense circuits (because i think it will be too expensive to have a separate reference and force and sense for each DAC)

 

Can i use the same circuit and feed it to 2 DACs or more?  (I think there would be problems because of the code dependant current of each DAC)

Should i use 1 reference voltage for all of the DACs and 1 force and sense circuit for each DAC?  (That is my personal choice)

Or do i have to use a Vref and force and sense circuit for each and every one of the DACs  (pretty expensive in my oppinion)

 

Thank you very much and best regards

 

 

  • 0
    TI__Mastermind 43915 points

    Hi JACR,

    Depending on your component placement and layout, you may be able to just use one reference source (we recommend buffering it) to drive two or more DAC8871s. I would recommend making sure they each have a separate cap directly at their reference input to help hold the voltage. You can tie the force and sense pins together at each individual DAC input and then connect the reference to those lines. The force and sense circuitry comes in handy when your reference voltage buffer is a descent distance away from your DAC. It allows you to have longer traces without having to worry about a current dependent voltage drop across the line resistance. You are correct that the current is code dependent so as long as your source is able to provide enough current, and provide it quickly, it should be able to drive multiple devices.

    Regards,

    Tony Calabria

  • 0 in reply to Tony Calabria
    Intellectual 270 points

     

    Thank you Tony for your time, and let me tell you that your answer was perfectly clear and i guess now i wont have to worry about the force and sense circuits because the Vref is pretty close to the DACs so i dont think i will have problems with that.

     

    Best Regards,

     

    Jairo Cala