Cirrus Logic CS4373A - Manual (Page 19)

CS4373A
DS699F2 19
5. OPERATIONAL MODES
The CS4373A has six operational modes and
two sleep modes selected by the MODE2,
MODE1, and MODE0 pins.
5.1 Sleep Modes
Sleep modes (MODE 0, 7) save power during
normal acquisition by turning off the AC and
DC test circuitry after system self-tests are
complete. In sleep mode the OUT and BUF
analog outputs are high impedance.
5.2 AC Test Modes
AC test modes use the digital test bit stream
(TBS) input from the CS5376A digital filter to
construct analog AC waveforms. The digital bit
stream input to the TDATA pin encodes the
analog waveform as over-sampled one bit
∆Σ
data, which is then converted into precision
differential or common mode analog AC sig-
nals by the CS4373A.
5.2.1 AC Differential
The first three AC test modes (MODE 1, 2, 3)
create precision differential analog signals for
THD and impulse testing of the measurement
channel. In mode 1, both sets of differential an-
alog outputs (OUT and BUF) are enabled. In
mode 2 only the OUT analog output is en-
abled, and BUF is high impedance. In mode 3
only the BUF analog output is enabled, and
OUT is high impedance.
Differential AC signals out of the CS4373A
consist of two halves with equal but opposite
magnitude, varying about a common mode
voltage. A full-scale 5 V
PP
differential AC sig-
nal centered on a -0.15 V common mode volt-
age will have:
SIG+ = -0.15 V + 1.25 V = +1.1 V
SIG- = -0.15 V - 1.25 V = -1.4 V
SIG+ is +2.5 V relative to SIG-
Table 2. Operational Modes
Selection MODE[2:0] Mode Description
0 0 0 0 Sleep mode.
1 0 0 1 AC OUT and BUF outputs.
2 0 1 0 AC OUT only, BUF high-z.
3 0 1 1 AC BUF only, OUT high-z.
4 1 0 0 DC common mode output.
5 1 0 1 DC differential output.
6 1 1 0 AC common mode output.
7 1 1 1 Sleep mode.
OUT+
OUT-
BUF+
BUF-
CS4373A
MODE 1
Maximum
5 Vpp
Differential
Maximum
5 Vpp
Differential
OUT+
OUT-
BUF+
BUF-
CS4373A
MODE 2
Maximum
5 Vpp
Differential
High
Impedance
OUT+
OUT-
BUF+
BUF-
CS4373A
MODE 3
High
Impedance
Maximum
5 Vpp
Differential
Figure 8. AC Differential Modes