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Internal VREF of 4.0V Using 3.0V Supply

Benjamin Tan
Prodigy 130 points
Other Parts Discussed in Thread: ADS1298

Internal VREF of 4.0V Using 3.0V Supply

I'm trying to measure a signal from 0-4V using the ADS1298ECG-FE and internal VRef.  However, I am unable to generate the VRef of 4.0V using the supply voltage of 3.0 (AVDD to AVSS).  When using supply voltage of 3.0V and configured to get VRef of 2.4V, I get the expected 2.4V at VREFP to VREFN.  When I reconfigure to get 4.0V still using 3.0V supply, I get ~3.0V at (VREFP to VREFN).  Is the device capable of generating VRef of 4.0V with a 3.0V supply?  Would I have to change supply voltage to 5.0V by replacing U10 as suggested in Table 2 of manual (SBAU171) to generate VRef of 4.0V?

Thanks,

Ben

  • 0
    TI__Guru**** 180931 points

    Hi Ben,

    The ADS1298 cannot generate a reference of 4V when powered from a 3V supply.  You need to power it at 5V which you can do by changing U10 or, you could simply remove the jumper at JP2 completely and use a clean 5V bench supply to apply power directly to pin 2 of JP2 referenced to TP2.  With a PGA gain set to 1 and 2.0VDC applied to IN(-) you can apply a single ended 0-4V to IN(+).