CS4226 Datasheet, PDF (38/60 Pages) Cirrus Logic – Surround Sound Codec

CDB4226
CDB4226 SYSTEM OVERVIEW
The CDB4226 evaluation board is designed to al-
low thorough evaluation of the CS4226 surround
sound codec. Six RCA jacks allow input of up to
three stereo signal sources to the analog input mul-
tiplexer of the CS4226, plus one RCA jack for a
monaural auxiliary input. One of the stereo pairs
can be selected for the stereo 20 bit ADCs, while
the auxiliary input is sent to the mono 20-bit ADC.
The CS4226 also has six 20-bit DACs, whose out-
puts are filtered, buffered, and routed to six RCA
jacks. Digital audio S/PDIF signals can be input to
the CS4226’s S/PDIF receiver through optical and
coaxial connectors. A CS8402A digital audio
transmitter provides optical and coaxial S/PDIF
outputs. Serial audio data I/O is provided by the
AUX port and the DSP port. Both ports can be con-
figured to operate with numerous interface formats.
The CS4226 supports software control via the SPI
and I²C interfaces. A DB-25 connector is provided
to allow connection to the serial control port. PC
software is provided which establishes an SPI in-
terface using the PC’s printer port. This software
provides a means for the user to read and write the
control registers on the CS4226.
The CDB4226 schematic has been partitioned into
10 small schematics shown in Figures 3
through 12.
POWER SUPPLY CIRCUITRY
Power is supplied to the evaluation board by six bind-
ing posts as shown in Figure 3. +5 VA and AGND
provide 5 Volt power to the CS4226. The +/-12 V
binding posts provide power to the analog input and
output buffers. The +5 VD and GND binding posts
supply 5 Volt power to the digital section of the board.
All power supply connections are equipped with tran-
sient suppression diodes and bulk filtering capacitors.
ANALOG INPUTS
The CS4226 is capable of switching between three
stereo pairs of line level inputs, and is equipped with
a mono auxiliary input. The desired input is selected
by setting the AIS1/0 bits in the ADC Control Byte
and the CSP bit in the AUX Port Control Byte (con-
sult the CS4226 data sheet for details on the config-
uration registers). The seven analog inputs (AIN1L,
AIN1R, AIN2L, AIN2R, AIN3L, AIN3R, and AIN-
AUX) are low-pass filtered and buffered, as shown
in Figures 4 and 5 (-3 dB at 200 kHz). The AC cou-
pling caps (C56-C62) allow the input pins of the
CS4226 to self-bias to approximately 2.3 Volts. A
nominal amplitude of 1 Vrms to these inputs will
achieve a full scale digital output from the A/D con-
verters in the CS4226. All inputs are noninverting.
AIN1L, AIN1R, and AINAUX are dedicated ana-
log input connections to the CS4226. However,
AIN2L, AIN2R, AIN3L, and AIN3R can also func-
tion as digital outputs (Figure 5). The output names
are FREQ0, FREQ1, AUTODATA, and /AUDIO,
respectively. When configured as outputs, these
pins provide channel status information from the
on-chip S/PDIF receiver (consult the CS4226 data
sheet for details on pinout functionality). The status
of these pins can be monitored with the LED’s pro-
vided (D8-D9). The four jumpers HDR5-HDR8,
defined in Table 1, are used in conjunction with the
CSP bit in the Auxiliary Port Control Byte to con-
figure these pins. When the CSP bit is a logic low,
the pins become analog inputs. In this configura-
tion, HDR5-HDR8 should be placed in the AIN po-
sition. When the CSP bit is a logic high, the pins
become digital outputs; in this case HDR5-HDR8
should be placed in the CSOUT position. Note that
the four jumpers should each be set to the same cor-
responding position.
The CS4226 also supports a differential input mode
in which the single-ended inputs AIN3L and
AIN2L become differential inputs AINL+ and
AINL-, respectively. Likewise, the single-ended
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DS188DB1