Cirrus Logic CDB5351 - Manual (Page 3)

DS565DB3 3
CDB5351
1. CDB5351 SYSTEM OVERVIEW
The CDB5351 evaluation board is an excellent means of quickly evaluating the CS5351. The CS8406 dig-
ital audio interface transmitter provides an easy interface to digital audio signal analyzers including the
majority of digital audio test equipment.
The CDB5351 schematic has been partitioned into 7 schematics shown in Figure 2 through Figure 8 . Each
partitioned schematic is represented in the system diagram shown in Figure 1 . Notice that the system dia-
gram also includes the interconnections between the partitioned schematics.
2. CS8406 DIGITAL AUDIO TRANSMITTER
The system generates and encodes standard S/PDIF data using a CS8406 Digital Audio Transmitter
(See
Figure 6 ). The outputs of the CS8406 are RS422 compatible differential line drivers. The CS8406
supports both Left Justified and I
2
S data formats, as determined by the DIP switch, S2. A description of
the CS8406 is included in the CS8406 datasheet.
3. INPUT/OUTPUT FOR CLOCKS AND DATA
The evaluation board has been designed to allow interfacing to external systems via the 10-pin header, J13.
The schematic for the clock/data input/output is shown in
Figure 5 .
The CDB5351 allows some flexibility as to the generation of the clocks. When the CS5351 and CS8406
are in slave mode, the SCLK and LRCK must be provided via the header, J13. MCLK must be generated
from the on board oscillator, Y1. This oscillator is socketed to allow other frequency oscillators to be used.
4. POWER SUPPLY CIRCUITRY
Power is supplied to the evaluation board by six binding posts (-12V, +12V, VD, VL, GND, +5 V),
see
Figure 8 . -12V and +12V supply the input amplifiers while the VD input supplies the VD pin of the
CS5351. VL supplies power to the VL pin of the CS5351 and to the level shifter circuits. The +5 V input
supplies power to the +5 V digital circuitry and the VA pin of the CS5351.
5. GROUNDING AND POWER SUPPLY DECOUPLING
The CS5351 requires careful attention to power supply and grounding arrangements to optimize perfor-
mance.
Figure 3 details the power distribution used on this board. The decoupling capacitors are located
as close to the CS5351 as possible. Extensive use of ground plane fill in the evaluation board yields large
reductions in radiated noise.
6. ANALOG INPUT FILTER
The CDB5351 implements a single-ended analog input buffer, as shown in Figure 2 . Note that there is no
attenuation associated with the input buffer, so a 1 Vrms input applied at the RCA connectors will provide
a full-scale 1 Vrms input to the CS5351.