Cirrus Logic CDB4382 - Manual (Page 4)

CDB4382
4
in either SPI

or I
2
C mode; however, in SPI mode
the CS4382 registers are write-only.
7. DSD OPERATION
The CDB4382 supports Direct Stream Digital
(DSD) operation through the header for external
clocks and data, J16. The CS4382 must be placed
into the DSD mode and headers J6 and J14 must be
set accordingly. See Table 2 for more information.
8. ANALOG OUTPUT FILTER
The analog output filter on the CDB4382 has been
designed to add flexibility when evaluating the
CS4382. The output filter was designed in an op-
tional two stage format, with the first optional stage
being an instrumentation amplifier design and the
second is a 2-pole butterworth filter.
The 2-pole filter is designed to have the in-band
impedance matched between the positive and neg-
ative legs. It also provides a balanced to single end-
ed conversion for standard un-balanced outputs.
The instrumentation amplifier is optionally insert-
ed by changing the FILT jumpers to position 2 (se-
lectable per channel by J37 & 38, J39 & 40, etc.).
This instrumentation amplifier incorporates a 5x
gain (+14dB) which effectively lowers the noise
contribution of the 2-pole filter which improves the
overall dynamic range of the system. The gain of
this stage is determined from the following equa-
tion:
The resistor designated by R
2
(see Figure 1) can be
adjusted to change the gain of the Instrumentation
amp, and the feedback resistors on the two sides of
the instrumentation amp ‘R’ must be equal.
A resistor divider has been placed before the RCA
jack which brings the signal level back to 2 Vrms
(selectable per channel with jumpers J21 to J28).
Note: This resistor divider may introduce more dis-
tortion from the second filter stage’s op-amp..
Table 1. System Connections
Gain 1
2 R
( )
R2
----------- + =
Figure 1. Instrumentation Amplifier Configuration
CONNECTOR INPUT/OUTPUT SIGNAL PRESENT
+5V Input + 5 Volt power
VD Input + 2.5 to +5V power for the CS4382 digital supply
VLS Input + 1.8 to +5V power for the CS4382 serial interface
VLC Input + 1.8 to +5V power for the CS4382 control interface
-18V Input -18 to -5V negative supply for the op-amps
+18V Input +5 to +18V positive supply for the op-amps
GND Input Ground connection from power supply
SPDIF INPUT - J2 Input Digital audio interface input via coax
SPDIF INPUT - OPTO-1 Input Digital audio interface input via optical
PCM INPUT - J15 Input Input for master, serial, left/right clocks and serial data
DSD INPUT - J16 Input Input for DSD data and clock
PC Port Input/Output Parallel connection to PC for SPI / I 2 C control port signals
EXT CTRL I/O Input/Output I/O for SPI / I 2 C control port signals
OUTA1 to OUTB4 Output Channels 1A to 4B line level analog outputs