CS5373A-ISZ View Datasheet(PDF) - Cirrus Logic
Part Name
Description
MFG CO.
'CS5373A-ISZ' PDF : 40 Pages View PDF
CS5373A
calibration and differential pulse tests. In mode
4, both sets of analog outputs (OUT and BUF)
are enabled.
5.3.2 DC Differential
The second DC test mode (MODE 5) enables
the modulator and DC test circuitry to create a
precision differential DC analog output voltage
as the final measurement for gain calibration
and as the step/pulse output for differential
pulse tests. In mode 5, both sets of analog out-
puts (OUT and BUF) are enabled.
In DC differential mode (MODE 5), level-shift-
ing buffer circuitry adds low-level 32 kHz
switched-capacitor noise to the DC output.
This noise is out of the measurement band-
width for systems designed with a
CS3301A / CS3302A amplifier and CS5373A
modulator and is rejected by the CS5378 digi-
tal filter. This 32 kHz noise does not affect DC
system tests, though it may be visible on an
oscilloscope at high gain levels.
By measuring both DC test modes
(MODE 4, 5), precision gain-calibration coeffi-
OUT+
OUT-
CS5373A
MODE 4
BUF+
BUF-
Approx
-0.15 VDC
Common
Mode
Approx
-0.15 VDC
Common
Mode
OUT+
OUT-
CS5373A
MODE 5
BUF+
BUF-
Maximum
2.5 VDC
Differential
Maximum
2.5 VDC
Differential
Figure 12. DC Test Modes
cients can be calculated for the measurement
channel. By first measuring the differential off-
set of the DC common mode output (MODE 4)
and then measuring the DC differential mode
amplitude (MODE 5), a precise offset-correct-
ed, volts-to-codes conversion ratio can be cal-
culated. This known ratio is then used along
with the CS5378 digital filter GAIN register to
normalize the full-scale amplitude to match
other channels in the measurement network.
By switching between DC common mode
(MODE 4) and DC differential mode
(MODE 5), pulse waveforms can be created to
characterize the step response of the mea-
surement channel. If a pulse test requires pre-
cise timing control, an external controller
should directly toggle the MODE pins of the
CS5373A to avoid delays associated with writ-
ing to the CS5378 digital filter GPIO register.
Sensor impedance can be measured using
DC differential mode (MODE 5), provided
matched series resistors are installed between
the BUF analog outputs and the sensor. Ap-
plying the known DC differential voltage to the
resistor-sensor-resistor string permits a ratio-
metric sensor impedance calculation from the
measured voltage drop across the sensor.
Switching between DC differential mode
(MODE 5) and modulator mode (MODE 0)
can, in the case of a moving-coil geophone,
test basic parameters of the electro-mechani-
cal transfer function. The voltage relaxation
characteristic of the sensor when switching the
analog outputs from a differential DC voltage
to high impedance depends primarily on the
geophone resonant frequency and damping
factor.
5.4 Sleep Mode
Sleep mode (MODE 7) saves system power
when measurements are not required by turn-
ing off the modulator, AC test circuitry, and DC
test circuitry. In sleep mode the modulator dig-
ital outputs and the BUF and OUT analog out-
puts are high impedance.
DS703F1
25
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