CDB42518 Cirrus Logic Inc, CDB42518 Datasheet - Page 4

• Manufacturer Part Number: CDB42518
• Description: BOARD EVAL FOR CS42518 CODEC
• Manufacturer: Cirrus Logic Inc

Specifications of CDB42518

• Main Purpose: Audio, CODEC
• Embedded: Yes, FPGA / CPLD
• Utilized Ic / Part: CS42518/16
• Primary Attributes: 6 Single-Ended Analog Inputs and 8 Outputs, S/PDIF Digital Audio Transmitter and Receiver
• Secondary Attributes: GUI, I2C, SPI Interfaces
• Product: Audio Modules
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant
• Other names: 598-1502

1. SYSTEM OVERVIEW
The CDB42518 demonstration board is an excellent means for evaluating the CS42518/16 family of highly integrat-
ed CODEC-S/PDIF receivers. Analog and digital audio signal interfaces are provided, as well as a DB-25 computer
parallel port interface for use with the supplied Windows configuration software.
The CDB42518 schematic set has been partitioned into 13 pages as shown in Figures 6 through 18.
1.1
A complete description of each member of the CS42518/16 family is included in each respective product data sheet.
1.2
The CS8406 S/PDIF transmitter on the demonstration board (see Figure 8) allows the performance of the CS42518
to be measured digitally. Either the CS42518 CODEC (CX) port or the Serial Audio Interface (SAI) port can be mul-
tiplexed to the CS8406. The CS8406 transmitter is configured to operate in slave mode only, and will receive the
required clocks from the CS42518. The data format for the CS8406 is selectable and must match that of its source.
The CS8406 must be configured using the supplied software.
1.3
There are two CS5361 A/D converters on the CS42518 demonstration board (see Figures 9 and 10). These con-
verters supply the CS42518 ADCIN signals, and must operate in left-justified, 24-bit mode only. Their serial data
outputs are used when supporting the CS42518 One Line Mode of operation.
RCA analog connectors supply the inputs to each CS5361 channel through a unity gain, AC-coupled, single-to-
differential circuit. Each CS5361 input circuit is biased to 1/2 VA, and a 1V
scale. The CS5361 converters are set to operate in slave mode and will receive their clocks from the CS42518. The
SCLK and LRCK signals can be provided from either the CS42518 CX or SAI port, and must be selected using the
configuration software.
1.4
Oscillator Y1 (see Figure 7) provides the System Clock (OMCK) for the CS42518. The crystal oscillator on the board
is mounted in pin sockets that allow it to be removed or replaced. The board is shipped with a 24.000 MHz crystal
oscillator stuffed at Y1. Please refer to the CS42518/16 data sheet for details on OMCK operation.
The buffer on the output of the oscillator provides for signal level shifting to the proper VLS supply. This buffer can
be removed if the oscillator is powered from the same VLS voltage source as the codec.
1.5
RCA phono connectors supply the CS42518 analog inputs through unity gain, AC-coupled single-to-differential cir-
cuits (see Figure 11). Each input circuit is biased to match the 2.7V
the CS42518 converter to full scale.
1.6
Each CS42518 analog output is routed through a differential to single-ended, unity-gain low pass filter, which is AC-
coupled to an RCA phono jack (see Figures 12 through 15). The analog output filter on the CDB42518 has been
designed to add flexibility when evaluating the CS42518 DAC outputs. The output filter was designed in a two stage
format, with the first stage being an optional instrumentation amplifier, and the second stage a 2-pole butterworth
low pass filter.
The 2-pole low pass filter provides an example of an inexpensive circuit with good distortion and dynamic range per-
formance. It is designed to have the in-band impedance matched between the positive and negative legs. It also
provides a balanced to single-ended conversion for standard un-balanced outputs. Evaluate this circuit by placing
the FILT jumpers (three per output channel) to position 1 (selectable by J9, J10 & J11 for OUTA1, etc.).
4
CS42518
CS8406
CS5361
Crystal Oscillator
Analog Input
Analog Outputs
DC
VQ, and a 1V
RMS
signal will drive the converter to full
RMS
differential signal will drive
CDB42518