Cirrus Logic CDB4398 - Manual (Page 3)

CDB4398
3
CDB4398 SYSTEM OVERVIEW
The CDB4398 evaluation board is an excellent means of quickly evaluating the CS4398. The CS8414 dig-
ital audio interface receiver provides an easy interface to digital audio signal sources including the majority
of digital audio test equipment. The evaluation board also allows the user to supply either PCM or DSD
clocks and data through headers for system development.
The CDB4398 schematic has been partitioned into 7 schematics shown in Figures 2 through 8. Each par-
titioned schematic is represented in the system diagram shown in Figure 1. Notice that the system diagram
also includes the interconnections between the partitioned schematics.
1. CS4398 DIGITAL TO ANALOG CONVERTER
A description of the CS4398 is included in the CS4398 datasheet.
2. CS8414 DIGITAL AUDIO RECEIVER
The system receives and decodes the standard S/PDIF data format using a CS8414 Digital Audio Receiver,
Figure 3. The outputs of the CS8414 include a serial bit clock, serial data, left-right clock (FSYNC), and
a 256 Fs master clock. The CS8414 data format is selected by switch S1. The operation of the CS8414 and
a discussion of the digital audio interface is included in the CS8414 datasheet.
The evaluation board has been designed such that the input can be either optical or coax, see Figure 3.
However, both inputs cannot be driven simultaneously.
3. INPUT/OUTPUT FOR CLOCKS AND DATA
The evaluation board has been designed to allow interfacing to external systems via the headers, J12 and
J14. Header J12 allows the evaluation board to accept externally generated PCM clocks and data. The
schematic for the clock/data input is shown in Figure 4.
Header J14 allows the evaluation board to accept externally generated DSD data and clock. The schematic
for the clock/data input is shown in Figure 4. A synchronous MCLK must still be provided via header J13.
Please see the CS4398 datasheet for more information.
4. POWER SUPPLY CIRCUITRY
Power is supplied to the evaluation board by seven binding posts (GND, +5V, VLS, VLC, VD, +12V and
-12V), see Figure 8. The VLC and VLS supplies can be jumpered to the +5V binding post for ease of use.
VD and VA should be set to the recommended values stated in the CS4398 datasheet. +12V and -12V sup-
ply power to the op-amps and can be +/-12 to +/-18 volts.
WARNING: Refer to the CS4398 datasheet for maximum allowable voltages levels. Operation outside of
this range can cause permanent damage to the device.
5. GROUNDING AND POWER SUPPLY DECOUPLING
The CS4398 requires careful attention to power supply and grounding arrangements to optimize perfor-
mance. Figure 2 details the connections to the CS4398 and Figures 9, 10, and 11 show the component
placement and top and bottom layout. The decoupling capacitors are located as close to the CS4398 as pos-
sible. Extensive use of ground plane fill in the evaluation board yields large reductions in radiated noise.