International Rectifier IRAUDAMP18 Reference Design
IRAUDAMP18
35W/4Ω x 2 Channel Class D Audio Power Amplifier
Using the IR4312
By
Jun Honda, Liwei Zheng
International Rectifier suggests the following guidelines for safe operation and
handling of IRAUDAMP18 Demo board;
Always wear safety glasses whenever operating Demo Board
Avoid physical contact with exposed metal surfaces when operating Demo
Board
Turn off Demo Board when placing or removing measurement probes
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CAUTION:
IRAUDAMP18 REV 1.0
TABLE OF CONTENTS ........................... PAGE
INTRODUCTION..............................................................................3
SPECIFICATIONS ...........................................................................3
CONNECTION SETUP ....................................................................4
TEST PROCEDURES......................................................................5
PERFORMANCE AND TEST GRAPHS ..........................................5
THERMAL INFORMATION..............................................................8
SCHEMATIC ....................................................................................9
IRAUDAMP18 BILL OF MATERIALS ............................................10
IRAUDAMP18 PCB SPECIFICATIONS.........................................11
REVISION CHANGES DESCRIPTIONS .......................................13
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IRAUDAMP18 REV 1.0
Introduction
The IRAUDAMP18 reference design is a two-channel, 35W/ch half-bridge Class D audio power
amplifier with single power supply. This reference design demonstrates how to use the IR4312 IC
with single power supply, implement protection circuits, and design an optimum PCB layout using
PowIRaudio integrated Class D IC. This reference design does not require additional heatsink or fan
cooling for normal operation (one-eighth of continuous rated power).The reference design provides all
the required housekeeping power supplies for ease of use. The two-channel design is scalable for
power and the number of channels.
Applications
Docking station audio systems
PC audio systems
Musical instruments
Karaoke amplifiers
Game consoles
Powered speaker systems
Car audio amplifiers
Features
Output Power: 35W x 2 channels (4Ω load)
Multiple Protection Features: Over-current protection (OCP), high side and low side
Over-voltage protection (OVP),
Under-voltage protection (UVP), high side and low side
Over-temperature protection (OTP)
PWM Modulator: Self-oscillating half-bridge topology
Specifications
General Test Conditions (unless otherwise noted) Notes / Conditions
Supply Voltages 18-31V
Load Impedance 2-4Ω Resistive load
Self-Oscillating Frequency 400kHz No input signal, Adjustable
Gain Setting 21.4dB 1Vrms input yields rated power
Electrical Data Typical Notes / Conditions
IR Devices Used IR4312 PowIRaudio integrated Class D IC
Modulator Self-oscillating, second order sigma-delta modulation, analog input
Power Supply Range 18-31V
Output Power CH1-2: (1% THD+N) 26W 1kHz
Output Power CH1-2: (10% THD+N) 35W 1kHz
Rated Load Impedance 2-4Ω Resistive load
Idling Supply Current 70mA No input signal
Total Idle Power Consumption 2.2W No input signal
Distortion 0.018% THD+N @ 3W, 4Ω
Residual Noise
Channel Efficiency 96%
180V
Single power supply;
IHF-A weighted, AES-17 filter
Single-channel driven, 35W, Class D
stage
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IRAUDAMP18 REV 1.0
Connection Setup
P2
P1
18-31 3A DC supply
P3
100W, Non-inductive Resistors
4 Ohm 4 Ohm
CH1
Output
CLIP
Indicator
Audio
Input
Audio Signal Generator
Connector Description
Audio IN CN1 Analog input for CH1 and CH2
POWER P3 Single supply
CH1 OUT P1 Output for CH1
CH2 OUT P2 Output for CH2
CH2
Output
Power
Indicator
IR4312
CN1
FAULT
Indicator
SW1
Fig 1 Typical Test Setup
SW1:PWM Shutdown/MUTE
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IRAUDAMP18 REV 1.0
Test Procedures
Test Setup:
1. Connect 4, 100W load to both output connectors, P1 and P2 and audio analyzer (Ap).
2. Connect Audio Signal Generator to CN1 for CH1 and CH2 respectively (Ap).
3. Connect a single power supply to P3 pre-adjusted to 18-31V as shown on Figure above
4. Turn on the power supply.
5. Turn on SW1(right side).
6. Blue LED (Normal) stays turning on after RED LED extinguished.
7. With an Oscilloscope, monitor switching waveform at VS of CH1 and CH2.
8. Quiescent current for the power supply should be 70mA 10mA at 31V.
Functionality Audio Tests:
9. Sweep the audio signal voltage from 15 mV
to 1.5 V
RMS
10. Monitor the output signals at P1/P2 with an oscilloscope. The waveform must be a non
distorted sinusoidal signal with input sinusoidal signal below 1Vrms.
RMS
.
Performance and Test Graphs
Power vs THD+N
Test Conditions:
Load Impedance = 4 ohms
VBus = 31V
Input Signal=1 kHz
10
5
THD+N vs Power
2
1
0.5
0.2
0.1
%
0.05
0.02
0.01
0.005
0.002
0.001
20m 4050m 100m 200m 500m 1 2 5 10 20
W
ColorSweep Trace Line Style Thick Data Axis Comment
1 1 Red Solid 2 Anlr.THD+N Ratio Left Ch1 4ohms 31V
1 3 B lue Solid 2 Anlr. THD+N Ratio Left Ch2 4ohms 31V
Fig 2
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IRAUDAMP18 REV 1.0
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