AN542 Datasheet, PDF (1/12 Pages) Silicon Laboratories – PERFORMANCE IMPROVEMENTS IN CLASS D AUDIO AMPLIFIERS

AN542
PERFORMANCE IMPROVEMENTS IN CLASS D AUDIO AMPLIFIERS
USING Si824X AUDIO DRIVERS
1. Introduction
The Si8241/44 Audio Gate Drivers facilitate high-fidelity, Class D amplification while offering many other
advantages over competing gate drivers. Based on Silicon Labs' proprietary CMOS isolation technology, these
drivers offer the benefits of:
 Precise dead time adjustment for low total harmonic distortion (THD) and high system efficiency
 Individually-isolated drivers to facilitate simpler system topologies and external component flexibility
 High functional integration for small installed size and competitive cost
The gate driver IC is a critical system component because it influences both system architecture and system
performance. The Si8241 Audio Gate Driver is a high-voltage driver capable of switching at frequencies up to
8 MHz to realize pre- or post-filter control. These devices have integrated precision dead time generators for low
THD and high efficiency, as well as isolated output drivers that eliminate the need for input level shifting and
facilitate the straightforward implementation of a two-state, half-bridge Class D amplifier.
This application note discusses the Silicon Labs Class D reference design, a stereo, two-state, half-bridge Class D
amplifier that delivers 120 W per channel into 8  or 150 W into 4 . The reference design and demo board is
available at www.silabs.com/isolation and uses the Si8241 Audio Gate Driver driven by a self-oscillating PWM
modulator, as shown in Figure 1.
Audio
In
Error Amplifier
-
+
Comparator
-
+
Si8241
5V
ISOdriver
VDDI
VDDA
PWM
VOA
GNDA
DT
VDDB
RDT
VOB
GND1 ^GNDB
VBOOT
Bootstrap
+50V
-50V
Feedback Amplifier
-
+
Figure 1. Si8241-Based Class D Amplifier Block Diagram
Speaker
Filter
Rev. 0.1 10/10
Copyright © 2010 by Silicon Laboratories
AN542