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ADS1220: Vref of ADS1220

Masami Michino
Genius 5070 points
Part Number: ADS1220

Dear, All

Customers are considering using ADS1220.
They want to use ANALOG INPUTS is single end.
So, the negative side becomes the voltage of AVSS.
Also, to convert plus/minus voltage signals, AVDD and AVSS use plus/minus power supply.
However, the provision of 'Recommended Operating Conditions' became a problem.
Vref = V(REFPx) - V(REFNx)
Is defined as 0.75V and the value of Max is defined as AVDD.
AVDD = +2.5V
AVSS = -2.5V
in the case of,
Vref = V(REFPx) - V(REFNx)
Is 2.5V the Max value?
Can it be used up to 5V?
Please tell me.
If it is 2.5V, they can not use it.

Thanks, Masami M.

  • 0
    TI__Guru** 113765 points

    Hi Masami,

    The ADS1220 when in bipolar AVDD supply mode (+/- 2.5V) can still have a 5V reference if the reference is REFN=-2.5V and REFP is +2.5V.  So the common point is at -2.5V for the reference.  Single-ended measurements are usually considered to have a common point of AGND.  So it is possible to have a 5V reference, but if the input is connected to AGND, then then maximum input voltage is AVDD (or 2.5V).  So in this case only 1/2 of the reference range can be used.

    At this point it is not clear to me why there is a desire for single-ended measurement and the need for bipolar analog supplies?  What is the output range of the sensor being connected?  There may still be a way to use the ADS1220 if the sensor is single-ended to AGND if I know more about what is being connected.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Genius 5070 points


    Hi, Bob-san,

    Thank you for your answer.
    Since the sensor used by customers is a sensor for bidirectional measurement, the output amplitude will be at the center of GND.
    With this specification, they are likely to be usable.

    Thanks, Masami M.