Cirrus Logic CDB4350 - Manual (Page 3)

DS691DB1 3
CDB4350
1. CDB4350 SYSTEM OVERVIEW
The CDB4350 evaluation board is an excellent platform for quickly evaluating the CS4350. The CS8416 digital 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 external PCM clocks and data through headers for
system development.
The CDB4350 schematic has been partitioned into 6 pages, shown in Figures 2 through 7 . Each schematic page is
represented in the system diagram shown in Figure 1 . Notice that the system diagram also includes the intercon-
nections between the partitioned schematics.
2. CS4350 DIGITAL-TO-ANALOG CONVERTER
A description of the CS4350 is included in the CS4350 datasheet, available at www.cirrus.com .
3. CS8416 DIGITAL AUDIO RECEIVER
The system receives and decodes the standard S/PDIF data format using a CS8416 digital audio receiver
(
Figure 5 ). The outputs of the CS8416 include a serial bit clock, serial data, and a left-right clock. The CS8416 data
format is selected through switch S1. The operation of the CS8416 and a discussion of the digital audio interface is
included in the CS8416 datasheet, available at
www.cirrus.com .
The CDB4350 has been designed so that the input can be either optical or coaxial (see Figure 6 ). However, both
inputs cannot be driven simultaneously.
After the CS8416 serial format is changed either through S1 in Stand-Alone Mode, or though the CDB4350 GUI in
PC Mode, a reset is required. The CS8416 can be manually reset using ‘HARDWARE RESET’ (S2) in Stand-Alone
Mode, or through software when operating the CDB4350 in PC Mode.
4. INPUT FOR CLOCKS AND DATA
The evaluation board has been designed to allow external PCM data input through header J10. The schematic for
the clock/data input is shown in
Figure 4 . In Stand-Alone Mode, switch position 6 of S4 selects the source as either
CS8416 (open) or header J10 (closed). In PC Mode, the PCM source is selected through software.
5. INPUT FOR CONTROL DATA
The evaluation board can be run in either a Stand-Alone Mode or with a PC. Stand-Alone Mode does not require
the use of a PC, and the mode pins are configured using switch positions 1 through 5 of S4 and switch positions 1
and 2 of S1. PC Mode uses software to set up the CS4350 through I²C
®
or SPI™ using the PC’s serial port or USB
port. When the serial port (RS232) or USB is attached and the CDB4350 software is running, PC Mode is automat-
ically selected.
Header J38 offers the option for external input of RST and SPI/I²C clocks and data. The board is set up from the
factory to use the on-board microcontroller in conjunction with software available at
www.cirrus.com . To use an ex-
ternal control source, remove the shunts on J38 and place a ribbon cable so the signal lines are on the center row
and the grounds are on the right side. R89 and R90 should be populated with 2 k
Ω resistors when using an external
I²C source which does not already provide pull-ups.