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IRAUDAMP18 REV 1.0
IRAUDAMP18
35W/4Ω x 2 Channel Class D Audio Power Amplifier
Using the IR4312
By
Jun Honda, Liwei Zheng
CAUTION:
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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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 Single power supply;
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 180V IHF-A weighted, AES-17 filter
Channel Efficiency 96% Single-channel driven, 35W, Class D
stage
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IRAUDAMP18 REV 1.0
Connection Setup
Fig 1 Typical Test Setup
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
CN1
P1 P2
P3
CH1
Output CH2
Output
Audio
Input
18-31 3A DC supply
4 Ohm 4 Ohm
Audio Signal Generator
IR4312
SW1
100W, Non-inductive Resistors
SW1:PWM Shutdown/MUTE
Power
Indicator
FAULT
Indicator
CLIP
Indicator
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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 mVRMS to 1.5 VRMS.
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.
Performance and Test Graphs
Power vs THD+N
Test Conditions:
VBus = 31V
Input Signal=1 kHz
Load Impedance = 4 ohms
ColorSweep Trace Line Style Thick Data Axis Comment
1 1 Red Solid 2 Anlr.THD+N Ratio Left Ch1 4ohms 31V
1 3 Blue Solid 2 Anlr.THD+N Ratio Left Ch2 4ohms 31V
0.001
10
0.002
0.005
0.01
0.02
0.05
0.1
0.2
0.5
1
2
5
%
20m 4050m 100m 200m 500m 1 2 5 10 20
W
THD+N vs Power
Fig 2
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IRAUDAMP18 REV 1.0
Frequency Response
Test Conditions:
VBus = 31V
Set Output = 1V
Load Impedance = 4 ohms
ColorSweep Trace Line Style Thick Data Axis Comment
1 1 Red Solid 2 Anlr.Level A Left Ch1 4ohm SP 25V
1 2 Blue Solid 2 Anlr.Level B Left Ch2 4ohm SP 25V
-10
+4
-8
-6
-4
-2
+0
+2
d
B
r
A
20 200k50 100 200 500 1k 2k 5k 10k 20k 50k 100k
Hz
Noise Floor
Test Conditions:
VBus = 31V
Load Impedance = 4 ohms
No Input Signal
ColorSweep Trace Line Style Thick Data Axis Comment
1 1 Red Solid 2 Fft.Ch.1 Ampl Left Ch1
1 2 Blue Solid 2 Fft.Ch.2 Ampl Left Ch2
-140
+20
-120
-100
-80
-60
-40
-20
+0
d
B
V
10 20k20 50 100 200 500 1k 2k 5k 10k
Hz
Fig 3
Fig 4
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IRAUDAMP18 REV 1.0
Noise Floor with 1Vrms Output
Test Conditions:
VBus = 31V
Output = 1Vrms @ 1 KHz
Load Impedance = 4 ohms
ColorSweep Trace Line Style Thick Data Axis Comment
1 1 Red Solid 2 Fft.Ch.1 Ampl Left Ch1 4ohm
1 2 Blue Solid 2 Fft.Ch.2 Ampl Left Ch2 4ohm
-100
+0
-80
-60
-40
-20
d
B
V
10 20k20 50 100 200 500 1k 2k 5k 10k
Hz
Efficiency
0.0%
10.0%
20.0%
30.0%
40.0%
50.0%
60.0%
70.0%
80.0%
90.0%
100.0%
0 5 10 15 20 25 30 35 40
Power (W)
Efficiency
Fig 5
Fig 6
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IRAUDAMP18 REV 1.0
Thermal Information:
1/8 Po Thermal Test
Conditions:
Tamb=25°C natural convection cooling
Both Channel Driven 1/8Po continuous 30mins
Temperature measured by infrared camera
Fig 7 IRAUDAMP18 (Vbus=31V)
IR4312’s temperature saturated around 75°C within 30minutes
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IRAUDAMP18 REV 1.0
Schematic
+B
VAA
R30
4.7R
C25
0.1uF
R41
1R
C15 1nF
C27
0.1uF,100V
Class D, AMP18 IR 43 12 S chemati c
SCH_4312 Rev1.2
D1
+B
SD
VCC
VSS
R31
4.7R C26
0.1uF
R42
1R
C17
1nF
C18
10uF,16V
C28
0.1uF,100V
C6
2.2nF,50V
C11
2.2nF,50V
C9
2.2nF,50V
C14 2.2nF,50V
D2
1N4148
R28
4.7R
D4
1N4148
IN-2
3
COMP2
2
CLIP
1
NC 30
VP2 24
VS2 25
GND
5
VS1 20
CSH2 27
CSH1
16
VB1
17
IN+1
8
VN2 22
NC 29
VP1
19
VS2 23
COM
15
VS1
18
VSS
6
IN-1
9
COMP1
10
IN+2
4
CSD
11
FAULT
12
NC
13
VCC
14
VN1 21
VB2 26
COM 28
VAA
7-B 31
OO
IC1
IR4312
C5 10uF,10V
C10 10uF,10V
R27
10K
VAA
DS1
DS2
R26
10K
VAA
D3
1N4148 D5
1N4148
C20
0.1uF
C19
0.1uF
C16
22uF,16V
R29
10K
DS3
R35
470R 1W
1
23
MJD44H11 T4 G
Q1
R34 4.7k
Z3
11V
CP5
22uF
+B
R45 2.2k
R43
10, 1W
LCH
D6
CT_PGND
1
2
P1
D7
C33
0.1uF, 63V
R46 2.2k
R44
10, 1W
RCH
CT_PGND
1
2
P2
C34
0.1uF, 63V
D9
D8
CT_SGND
C12
2.2nF,50V
R19 180R
R24
180R
C7
2.2nF,50V
R22 180R
VSS
R21 180R
C13
2.2nF,50V
R20 180R
R23
180R
C8
2.2nF,50V
R1100k
R3
330 C1
1nF
R4
330 C2
1nF
R11
*3.01k 1%
R15 47.5k 1%
R12
*3.01k 1%
R16 47.5k 1%
CT_SGND
CT_SGND
INPUT GND
R2100k
R5
330 C3
1nF
R6
330 C4
1nF
R13
*3.01k 1%
R17 47.5k 1%
R14
*3.01k 1%
R18 47.5k 1%
CT_SGND
CT_SGND
R48 10k, 1/2WR4910k, 1/2W
C36
0.1uF,100V
+
-
C37
0.1uF,100V
+B
GND
+B
GND 1
2
P3
R53
10k
Z5
16V
Z4
33V
R51
47k
R52
10k R55
47k
R56
10k
R57
47k
12
3
54
6
S1
SW SPDT
C35
0.1uF
Q2
MMBT5551
Q3
MMBT5551
+B
SD
OVP
UVP
+B
GND
GND
OFF
ON
CT_SGND CT_PGND
CT_PGND
GND
GND
INPUT GND
R50
10R0
CT_PGND GND
R8
220R 1W
R7
220R 1W
Z1
5.1V
GND
Z2
5.1V
+B
R47
NM
GND
+B
GND
GND
R25
47K
D10
L1
22uH
L2
22uH
C21
0.1uF,16V
VCC R32
2.7K
R33
2.7K
C31
0.47uF, 400V
C32
0.47uF, 400V
2
1
3
5
4
CN1
CP1
2.2uF
CP2
2.2uF
CP3
2.2uF
CP4
2.2uF
C38
2200uF, 25V
C39
2200uF, 25V
18V-31V Version
Fig 8
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IRAUDAMP18 REV 1.0
Bill of Materials
No Digikey P/N Designator Description Quantity Vender
1 399-1082-1-ND
C1, C2, C3, C4, C15,
C17
CAP CER 1000PF 50V 10% X7R
0603 6 Digikey
2 587-2668-1-ND C5, C10 CAP CER 10UF 10V 10% X7R 0805 2 Digikey
3 490-1500-1-ND
C6, C7, C8, C9, C11,
C12, C13, C14
CAP CER 2200PF 50V 10% X7R
0603 8 Digikey
4 587-1433-1-ND C16 CAP CER 22UF 16V 20% X5R 1206 1 Digikey
5 490-5519-1-ND C18 CAP CER 10UF 16V 10% X6S 0805 1 Digikey
6 311-1140-1-ND C19, C20 CAP CER 0.1UF 50V 10% X7R 0805 2 Digikey
7 311-1142-1-ND C21 CAP CER 0.1UF 16V 10% X7R 0805 1 Digikey
8 445-1418-1-ND C25, C26
CAP CER 0.1UF 100V 10% X7R
0805 2 Digikey
9 445-1377-1-ND C27, C28, C36, C37
CAP CER 0.1UF 100V 10% X7R
1206 4 Digikey
10 495-1315-ND C31, C32 CAP FILM 0.47UF 400VDC RADIAL 2 Digikey
11 BC2054-ND C33, C34 CAP FILM 0.1UF 63VDC RADIAL 2 Digikey
12 445-1418-1-ND C35
CAP CER 0.1UF 100V 10% X7R
0805 1 Digikey
13 565-1064-ND C38, C39
CAP ALUM 2200UF 25V 20%
RADIAL 2 Digikey
14 CP1-3545N-ND CN1
CONN JACK STEREO R/A 5PIN
3.5MM 1 Digikey
15 565-1103-ND CP1, CP2, CP3, CP4 CAP ALUM 2.2UF 50V 20% RADIAL 4 Digikey
16 565-1056-ND CP5 CAP ALUM 22UF 25V 20% RADIAL 1 Digikey
17 1N4148W-FDICT-ND
D1, D2, D3, D4, D5,
D10
DIODE SWITCH 100V 400MW
SOD123 6 Digikey
18 160-1181-1-ND DS1 LED RED CLEAR 0603 SMD 1 Digikey
19 160-1183-1-ND DS2 LED GREEN CLEAR 0603 SMD 1 Digikey
20 160-1646-1-ND DS3 LED BLUE CLEAR 0603 SMD 1 Digikey
21 IR4312 IC1
2 CH PowIRaudio integrated Class D
IC 1 IR
22 Sagami 7G14A-220M-R L1, L2
Power Inductors Class D Inductor
22uH 2
Inductors,
Inc
23 281-1414-ND P1, P2, P3
CONN TERM BLOCK PCB 5.0MM
2POS 3 Digikey
24 MJD44H11T4GOSCT-ND Q1 TRANS PWR NPN 8A 80V DPAK 1 Digikey
25 MMBT5551FSCT-ND Q2, Q3 TRANSISTOR NPN 160V SOT-23 2 Digikey
26 RMCF0603JT100KCT-ND R1, R2
RES 100K OHM 1/10W 5% 0603
SMD 2 Digikey
27 RMCF0603JT330RCT-ND R3, R4, R5, R6 RES 330 OHM 1/10W 5% 0603 SMD 4 Digikey
28 RMCF2512JT220RCT-ND R7, R8 RES 220 OHM 1W 5% 2512 SMD 2 Digikey
29 RHM3.01KCRCT-ND R11, R12, R13, R14 RES 3.01K OHM 1/8W 1% 0805 SMD 4 Digikey
30 311-47.5KCRCT-ND R15, R16, R17, R18 RES 47.5K OHM 1/8W 1% 0805 SMD 4 Digikey
31 RHM180GCT-ND
R19, R20, R21, R22,
R23, R24 RES 180 OHM 1/10W 5% 0603 SMD 6 Digikey
32 RHM47KGCT-ND R25 RES 47K OHM 1/10W 5% 0603 SMD 1 Digikey
33 RHM10KGCT-ND R26, R27, R29 RES 10K OHM 1/10W 5% 0603 SMD 3 Digikey
34 RMCF0603JT4R70CT-ND R28, R30, R31 RES TF 1/10W 4.7 OHM 5% 0603 3 Digikey
35 RHM2.7KGCT-ND R32, R33 RES 2.7K OHM 1/10W 5% 0603 SMD 2 Digikey
36 311-4.7KARCT-ND R34 RES 4.7K OHM 1/8W 5% 0805 SMD 1 Digikey
37 PT470XCT-ND R35 RES 470 OHM 1W 5% 2512 SMD 1 Digikey
38 P1.0ACT-ND R41, R42 RESISTOR 1.0 OHM 1/8W 5% 0805 2 Digikey
39 541-10.0AFCT-ND R43, R44 RES 10.0 OHM 1W 1% 2512 SMD 2 Digikey
40 RMCF0805JT2K20CT-ND R45, R46 RES 2.2K OHM 1/8W 5% 0805 SMD 2 Digikey
41 541-10KVCT-ND R48, R49 RES 10K OHM 1/2W 5% 1210 SMD 2 Digikey
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IRAUDAMP18 REV 1.0
42 RMCF0805JT10R0CT-ND R50 RES 10 OHM 1/8W 5% 0805 SMD 1 Digikey
43 RHM47KARCT-ND R51, R55, R57 RES 47K OHM 1/8W 5% 0805 SMD 3 Digikey
44 RHM10KARCT-ND R52, R53, R56 RES 10K OHM 1/8W 5% 0805 SMD 3 Digikey
45 360-1758-ND S1
SWITCH TOGGLE SPDT .4VA SEAL
PCB 1 Digikey
46 DDZ5V1BDICT-ND Z1, Z2
DIODE ZENER 5.1V 500MW SOD-
123 2 Digikey
47 BZT52C11-FDICT-ND Z3 DIODE ZENER 11V 500MW SOD123 1 Digikey
48 568-3766-1-ND Z4
DIODE ZENER 33V 375MW
SOD123F 1 Digikey
49 BZT52C16-FDICT-ND Z5
DIODE ZENER 16V 500MW SOD-
123 1 Digikey
PCB Specifications
PCB:
1. Two Layers SMT PCB with through holes
2. 1/16 thickness
3. 2/0 OZ Cu
4. FR4 material
5. 10 mil lines and spaces
6. Solder Mask to be Green enamel EMP110 DBG (CARAPACE) or Enthone Endplate
DSR-3241or equivalent.
7. Silk Screen to be white epoxy non conductive per IPC–RB 276 Standard.
8. All exposed copper must finished with TIN-LEAD Sn 60 or 63 for 100u inches thick.
9. Tolerance of PCB size shall be 0.010 –0.000 inches
10. Tolerance of all Holes is -.000 + 0.003”
11. PCB acceptance criteria as defined for class II PCB’S standards.
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IRAUDAMP18 REV 1.0
PCB Layout
Top side:
Fig9
Bottom side:
Fig10
Note: Refer to AN1170 for footprint and board mounting details.
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IRAUDAMP18 REV 1.0
Revision changes descriptions
Revision Changes description Date
Rev 1.0 Released May 11, 16 2012
WORLD HEADQUARTERS: 101 N. Sepulveda Blvd., El Segundo, California 90245 Tel: (310) 252-7105
Data and specifications subject to change without notice. 05/16/2012
