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ADS131A04: Virtual gnd of adc when using external voltage reference

Briquel Florian
Prodigy 30 points
Part Number: ADS131A04
Other Parts Discussed in Thread: REF5045

Hello,

I'm designing a design with ADS131A04 for current/voltage protection&metering application.

I plan to use adc @10ks/s sample rate and to fit all the signal dynamic I will need to be 20bits enob. Then I use an external voltage ref: a ref5045 (the max ref voltage for ads131a04 is 4.5V so I use the max ref voltage to optimize voltage input dynamic). I plan to use ads131 with a single rail voltage : 5VDC and create a virtual gnd. Question: with a 4.5V external voltage ref is the virtual gnd 2.25V or 2.5V ? I imagine with a 5VDC analog supply and a 4.5V external voltage ref the input range is 0 to 4.5V with a 2.25V virtual gnd, but I doubt about that, can you light my design ?

Thanks for help!

Best regard, Florian

  • 0
    TI__Mastermind 37875 points

    Hi Briquel,

    It's the midpoint of the analog supplies, 2.5V when a single 5V analog power supply is used. When the Vref is 4.5V, both AINxP and AINxN can swing from 2.5V+1/2Vref/Gain to 2.5V-1/2Vref/Gain, so the differential voltage at the maximum and minimum points is equal to Vref/Gain to -Vref/Gain which means 4.5V/Gain ~-4.5V/Gain in a differential configuration.

    Regards,

    Dale