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ADS1262: Current match requirements for sensing low noise signals

JS RAWAT
Prodigy 20 points
Part Number: ADS1262
Other Parts Discussed in Thread: ADS1220

Dear All, I been working on ADS1220 and ADS1262. Now I want to use IDAC1 and IDAC2 in a bridge network to read differential signal.

In data specifications it mentions current mismatch between these two current source is 0.1% to 1%. If I use them in two arms of bridge and get this mismatch I am worried that this mismatch will be reflected in my input signal which will reduce my ENOB drastically. ADS1262 has current swapping feature but still I don't think I will get ENOB greater than 20. 

My question is I fear trying current mirror in my circuit design. Or is my fear unfounded because current mirror is standard technique to deliver such accuracies. 

Before proceeding to PCB fabrication I want to weigh between usual ratiometric measurement versus current mirror measurement.

Thanks

JSR

  • 0
    TI__Mastermind 45215 points

    Hello JSR,

    Can you please let me know why you need two separate current sources? Are you trying to build a discrete mirror current to match the IDAC current? A single current source is typically used to drive both legs of a Wheatstone bridge. Alternatively, a bridge circuit excited with a constant voltage source is commonly designed in the market.

    Best Regards,

    Dale

  • 0 in reply to Dale Li
    Prodigy 20 points

    Thanks Dale I got your point. Yes I was under impression two matched but separate current sources are used in wheatstone bridge 

  • 0 in reply to JS RAWAT
    TI__Mastermind 45215 points

    Hello JSR,

    Thanks to confirm. I think it's not easy to design a discrete current source to match another current source very well. If a current excitation is still preferred by you, I suggest you can get a ADS1262EVM-PDK for a test and evaluation.

    Thanks&regards,

    Dale