Datasheet

AD7927 Data Sheet
Rev. D | Page 18 of 28
V
DRIVE
The AD7927 also has the V
DRIVE
feature. V
DRIVE
controls the volt-
age at which the serial interface operates. V
DRIVE
allows the ADC
to easily interface to both 3 V and 5 V processors. For example,
if the AD7927 were operated with an AV
DD
of 5 V, the V
DRIVE
pin
could be powered from a 3 V supply. The AD7927 has a larger
dynamic range with an AV
DD
of 5 V while still being able to
interface to 3 V processors. Take care to ensure V
DRIVE
does not
exceed AV
DD
by more than 0.3 V (see the Absolute Maximum
Ratings section).
THE REFERENCE
An external reference source should be used to supply the
2.5 V reference to the AD7927. Errors in the reference source
result in gain errors in the AD7927 transfer function and add
to the specified full-scale errors of the part. A capacitor of at
least 0.1 μF should be placed on the REF
IN
pin. Suitable refer-
ence sources for the AD7927 include the AD780, REF192, and
the AD1582.
If 2.5 V is applied to the REF
IN
pin, the analog input range can
be either 0 V to 2.5 V or 0 V to 5 V, depending on the setting of
the RANGE bit in the control register.