Cirrus Logic CRD44800 - Manual

1
Copyright © Cirrus Logic, Inc. 2004
(All Rights Reserved)
Cirrus Logic, Inc.
www.cirrus.com
CRD44800
50 W Half-Bridge Reference Design for the CS44800
Features
Eight half-bridge channels, 50 W each
Least amount of discrete components per
channel
Programmable load compensation
Power Supply Rejection (PSR) feedback
allowing amplifier to operate from low cost
linear unregulated power supplies
Peak signal limiting
Thermal and over-current protection
> 85% amplifier efficiency
Works with GUI to configure the board or in
a standalone mode for easy operation.
Demonstrates recommended layout and
grounding arrangements
Description
The CRD44800 PWM Amplifier demonstrates the
CS44800, Cirrus’ eight-channel pure digital PMW con-
troller. This reference design implements an eight-
channel amplifier which delivers 50 W per half-bridge
channel into 6
Ω loads using a single +45 V supply (at
10% THD+N). A 155 W Switched Mode Power Supply
(SMPS) is used to power the CRD44800.
As shown below, the CS44800 IC takes four stereo dig-
ital audio inputs in I²S format and converts them to PWM
outputs. This 64-pin LQFP IC provides an integrated
sample rate converter for 32 kHz-192 kHz input sample
rate support, volume up/down, speaker load compensa-
tion, PopGuard® to prevent pops in single voltage rail
half-bridge applications, peak limiting to prevent amplifi-
er clipping, power supply ripple compensation, and AM
frequency interference elimination.
This reference design uses the the Philips TDA8939, an
integrated power stage back end for digital amplifiers
(four TDA8939 parts configured as half-bridges are used
for this eight-channel design). Current limiting and ther-
mal protection are provided by the TDA8939.
The inductor/capacitor 2 nd order low pass filter (LPF) re-
moves high frequency components from the output
signal effectively converting it from digital to analog.
ORDERING INFORMATION
CRD44800 Reference Design
I
Philips
TDA8939 CS44800
(PWM Controller)
LPF
LPF
6
Ω
6
Ω
Channels 1 and 2 (of 8)
To channels 3/4
To channels 5/6
To channels 7/8
PWM Outputs
+45V
CS4461 ADC
+45V
PSR Circuitry
Audio Driver Board
I 2 S Clocks & Data
I 2 C Host Control
155W Switched Mode
Power Supply
+45V/+5V
DEC ‘04
DS632RD2