
AD7322
Preliminary Technical Data
REFERENCE
The AD7322 can operate with either the internal 2.5V on-chip
reference or an externally applied reference. The internal
reference is selected by setting the REF bit in the Control
Register to 1. On power up the REF bit will be 0, selecting the
external Reference for the AD7322 conversion. For external
reference operation the REF
IN
/REF
OUT
pin should be decoupled
to AGND with a 470 nF capacitor.
The internal Reference circuitry consists of a 2.5V band gap
reference and a reference buffer. When operating the AD7322 in
internal Reference mode the 2.5V internal reference is available
at the REF
IN
/REF
OUT
pin. When using the AD7322 with the
internal reference the REFIN/REFOUT pin should be
decoupled to AGND using a 0.47 μF cap. It is recommended
that the Internal Reference be buffered before applying it else
where in the system.
The AD7322 is specified for a 2.5V to 3V reference range. When
a 3V reference is selected the ranges will be, ±12V, ±6V, ±3V
and 0 to 12V. For these ranges the V
DD
and V
SS
supply must be
equal to or greater than the max Analog Input Range selected.
On power up if the internal reference operation is required for
the ADC conversion, a write to the control register is necessary
to set the REF bit to 1. During the Control Register write the
conversion result from the first initial conversion will be invalid.
The reference buffer will require TBD us to power up and
charge the 0.47 μF decoupling cap, during the power up time
the conversion result from the ADC will be invalid.
Rev. PrE | Page 15 of 18