CS4373A Datasheet, PDF (24/34 Pages) Cirrus Logic – Low-power, High-performance Test DAC

CS4373A
SENSOR
CH1 BUF
CH2 BUF
CH3 BUF
CH4 BUF
ELECTRONICS
CH1,2,3,4 OUT
VA+
VA-
2.5 V
VREF
SWITCH
CONTROL
VA+
0.1µF
VA-
0.1µF
VD
Analog
Switches
10nF
C0G
CAP+
CAP-
Route BUF as diff pair BUF+
BUF-
MCLK
MSYNC
TDATA
10 Ω
100µF
Route OUT as diff pair
CS4373A
OUT+
OUT-
MODE0
MODE1
MODE2
Route VREF as diff pair VREF+
VREF-
+
VA-
VA-
0.1µF
ATT0
ATT1
ATT2
DGND
VD
MCLK
MSYNC
TBSDATA
GPIO
GPIO
GPIO
GPIO
GPIO
GPIO
CS5376A
SIGNALS
Figure 12. Analog Outputs
7. ANALOG OUTPUTS
The CS4373A has multiple differential analog
outputs. The best possible analog perfor-
mance is achieved from the precision outputs
(OUT±), but with only minimal drive capability.
A buffered output (BUF±) can drive an external
load, but with reduced analog performance.
The internal anti-alias filter requires a dedicat-
ed capacitor connection (CAP±) to eliminate
undesired high-frequency signals.
7.1 Differential Signals
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-
For the opposite case:
SIG+ = -0.15 V - 1.25 V = -1.4 V
SIG- = -0.15 V + 1.25 V = +1.1 V
SIG+ is -2.5 V relative to SIG-
So the total swing for SIG+ relative to SIG- is
(+2.5 V) - (-2.5 V) = 5 V_pp differential. A similar
calculation can be done for SIG- relative to
SIG+. It’s important to note that a 5 V_pp differ-
ential signal centered on a -0.15 V common
mode voltage never exceeds +1.1 V with re-
spect to ground and never drops below -1.4 V
with respect to ground on either half. By defini-
tion, differential voltages are measured with
respect to the opposite half, not relative to
ground. A voltmeter differentially measuring
between SIG+ and SIG- in the above example
would read 1.767 V_rms, or 5 V_pp.
7.2 Analog Output Attenuation
The CS4373A has seven analog output atten-
uation settings from 1/1 to 1/64 selected with
the ATT2, ATT1, and ATT0 pins. At 1/64 atten-
uation in AC Common Mode (MODE 6) there
is no output signal amplitude due to the atten-
uator architecture.
Selection
0
1
2
3
4
5
6
7
ATT[2:0]
000
001
010
0 11
100
101
11 0
111
Attenuation
1/1
1/2
1/4
1/8
1/16
1/32
1/64
reserved
dB
0 dB
-6.02 dB
-12.04 dB
-18.06 dB
-24.08 dB
-30.10 dB
-36.12 dB
reserved
Table 3. Output Attenuation Settings
24
DS699F2