Cirrus Logic CS5373A - Manual (Page 32)

CS5373A
32 DS703F2
with MCLK.
The voltage reference external RC filter series
resistor creates a voltage divider with the
VREF input impedance to reduce the effective
applied input voltage. To minimize gain error
resulting from this voltage divider effect, the
RC filter series resistor should be the minimum
size recommended in the voltage reference
device data sheet.
8.5 VREF Accuracy
The nominal voltage reference input is speci-
fied as 2.500 V across the VREF
± pins, and all
CS5373A gain accuracy specifications are
measured with a nominal voltage reference in-
put. Any variation from a nominal VREF input
will proportionally vary the analog full-scale
gain accuracy.
Since temperature drift of the voltage refer-
ence results in gain drift of the analog full-scale
amplitude, care should be taken to minimize
temperature drift effects through careful selec-
tion of passive components and the voltage
reference device itself. Gain drift specifications
of the CS5373A do not include the tempera-
ture drift effects of external passive compo-
nents or of the voltage reference device itself.
8.6 VREF Independence
If the test signal source is required to be fully
independent of the measurement channel, the
CS5373A device cannot be used. Instead, a
CS5371 modulator and a CS4373A test DAC
should be used and connected to two indepen-
dent voltage reference devices. This will elimi-
nate the possibility for undetected ratiometric
errors when the same voltage reference de-
vice is used by both the test signal source and
the measurement channel.
Because modern precision voltage references
are highly reliable, requirements for separate
modulator and test DAC voltage references
should be considered carefully. In the unlikely
event of voltage reference failure independent
of other system components, the CS5373A
volts-to-codes ratio will be out of spec and
measurement channel performance will be
poor during system self-tests.