AD7788: Input ranges

Document created by analog-archivist Employee on Feb 23, 2016
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From the specified common mode range it should be possible to operate the
AD7788/90 on Vdd = +5V as follows:
REFIN- connected to GND, REFIN+  conneceted to VDD/2.
AIN- is connected to GND, AIN+ is the input for a voltage derived from Vdd by a
variable resistive divider, and is in the range of 0V...+5V.

If the input overloaded?

Do we have to expect restrictions on accuracy from the offset? If yes, by what
degree and above/below  of which limits?

 

The inputs of these devices are DIFFERENTIAL.

If you ground AIN- then you can only use the positive
half-scale at unity gain since AIN+ may not be more
than 30mV below the negative rail - and Vin(max) will
be +2.5 V and you will lose the lower half of the
5 V span.

If you want a 0-5 V span you must bias AIN- to +2.5V
and apply 0 - +5 V to AIN+.

The offset of these devices is 3 uV so should not
be a problem.

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