Is it possible to use different external reference options on the AD7626? (the datasheet states that only a 4.096V reference is possible)
There are three reference options on the AD7626.
1) Internal reference and internal reference buffer
2) External 1.2V reference and internal reference buffer
3) External 4.096V reference
Is is not possible to use other varying options. All of these modes mean that a 4.096V reference will be applied to the ADC and the full analog input range will be +/- 4.096V differential.
the datasheet for the AD7626/Ad7625 show the buexternal ref bufffering of the external 4V096 ref before being applied to the REF pins - I dont see in the datasheet the current requirements on the external Ref.
What would the effect on performance be if the buffering was omitted, please assume that the ADR444 is the ref.
The buffer is required to replenish the charge on the 10uF cap between conversions. If you remove the buffer the ADR444 may not be able to charge the cap in time depending on the sample rate you run at. This would impact performance as the reference would not be settled in time for the next conversion. A larger cap like 22uF may help but i can't say exactly how performance would be affected as it will depend on throughput rate etc.
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