IRF IRAUDAMP6 User manual

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IRAUDAMP6 REV 1 .0
IRAUDAMP6
250W/8Ω x 2 Channel Class D Audio Power Am lifier
Using the IRS20957S and IRF6785
By
Jun Hon a, Jorge Cerezo an Liwei Zheng
CAUTION:
International Rectifier suggests the following guidelines for safe o eration and handling of
IRAUDAMP6 Demo board;
• Always wear safety glasses whenever o erating Demo Board
• Avoid hysical contact with ex osed metal surfaces when o erating Demo Board
• Turn off Demo Board when lacing or removing measurement robes

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IRAUDAMP6 REV 1 .0
TABLE OF CONTENTS PAGE
INTRODUCTION............................................................................................................................................... 3
SPECIFICATIONS ............................................................................................................................................ 3
CONNECTION SETUP ..................................................................................................................................... 5
CONNECTOR DESCRIPTION ......................................................................................................................... 6
TEST PROCEDURES....................................................................................................................................... 6
PERFORMANCE AND TEST GRAPHS .......................................................................................................... 7
IRAUDAMP6 OVERVIEW .............................................................................................................................. 12
FUNCTIONAL DESCRIPTIONS..................................................................................................................... 13
CLASS D OPERATION..................................................................................................................................... 13
POWER SUPPLIES.......................................................................................................................................... 13
BUS PUMPING ............................................................................................................................................... 14
HOUSE KEEPING POWER SUPPLY................................................................................................................... 14
INPUT............................................................................................................................................................ 15
OUTPUT ........................................................................................................................................................ 15
LOAD IMPEDANCE .......................................................................................................................................... 15
GAIN SETTING / VOLUME CONTROL ................................................................................................................ 16
EFFICIENCY................................................................................................................................................... 16
OUTPUT FILTER DESIGN AND PREAMPLIFIER................................................................................................... 17
SELF-OSCILLATING PWM MODULATOR .......................................................................................................... 17
ADJUSTMENTS OF SELF-OSCILLATING FREQUENCY......................................................................................... 18
SWITCHES AND INDICATORS ........................................................................................................................... 18
STARTUP AND SHUTDOWN ............................................................................................................................. 18
CLICK AND POP NOISE REDUCTION ............................................................................................................... 19
STARTUP AND SHUTDOWN SEQUENCING ........................................................................................................ 20
SELECTABLE DEAD-TIME................................................................................................................................ 23
LEVEL SHIFTERS ........................................................................................................................................... 23
PROTECTION SYSTEM OVERVIEW ................................................................................................................... 24
Over-Current Protection (OCP)............................................................................................................... 24
Over-Voltage Protection (OVP)............................................................................................................... 26
Under-Voltage Protection (UVP) ............................................................................................................. 26
Speaker DC-Voltage Protection (DCP)................................................................................................... 27
O set Null (DC O set) Adjustment ......................................................................................................... 27
Over-Temperature Protection (OTP) ...................................................................................................... 27
Thermal Considerations .......................................................................................................................... 27
Thermal Inter ace Material’s Pressure Control ....................................................................................... 28
AMP6 Thermal pad pressure control calculation .................................................................................... 30
Short Circuit Protection Response.......................................................................................................... 31
IRAUDAMP6 FABRICATION MATERIALS................................................................................................... 37
IRAUDAMP6 PCB SPECIFICATIONS........................................................................................................... 42
REVISION CHANGES DESCRIPTIONS........................................................................................................ 46

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IRAUDAMP6 REV 1 .0
Introduction
The IRAUDAMP6 reference esign is a two-channel, 250W/ch (8Ω) loa half-bri ge Class D au io power
amplifier. This reference esign emonstrates how to use the IRS20957S Class D au io controller an gate
river IC, implement protection circuits, an esign an optimum PCB layout using the IRF6785 DirectFET
MOSFETs. This reference esign oes not require increasing the size of the heatsink or require fan cooling
for normal operation (one-eighth of continuous rate power).The reference esign provi es all the require
housekeeping power supplies for ease of use. The two-channel esign is scalable for power an the number
of channels.
A lications
• AV receivers
• Home theater systems
• Mini component stereos
• Powere speakers
• Sub-woofers
• Musical Instrument amplifiers
Features
Output Power: 250W x 2 channels (8Ω loa ),
Resi ual Noise: 90µV, IHF-A weighte , AES-17 filter
Distortion: 0.005% THD+N @ 125W, 8Ω
Efficiency: 96% @ 250W, 8Ω, single-channel riven, Class D stage
Multiple Protection Features: Over-current protection (OCP), high si e an low si e
Over-voltage protection (OVP),
Un er-voltage protection (UVP), high si e an low si e
DC-protection (DCP),
Over-temperature protection (OTP)
PWM Mo ulator: Self-oscillating half-bri ge topology with optional clock synchronization
S ecifications
General Test Conditions (unless otherwise noted) Notes / Conditions
Supply Voltages ±73.5V
Loa Impe ance 8-4Ω
Self-Oscillating Frequency 400kHz No input signal, A justable
Gain Setting 33 B 1Vrms input yiel s rate power
Electrical Data Ty ical Notes / Conditions
IR Devices Use IRS20957S Au io Controller an Gate-Driver,
IRF6785 DirectFET MOSFETs
Mo ulator Self-oscillating, secon or er sigma- elta mo ulation, analog input
Power Supply Range ± 38V to ±75V Bipolar power supply
Output Power CH1-2: (1% THD+N) 320W 1kHz
Output Power CH1-2: (10% THD+N) 410W 1kHz

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IRAUDAMP6 REV 1 .0
Rate Loa Impe ance 8-4Ω Resistive loa
I ling Supply Current ±85mA No input signal
Total I le Power Consumption 11.9W No input signal
Channel Efficiency 96% Single-channel riven,
250W, Class D stage
.
Audio Performance
* Before
Demodula
tor
Class D
Out ut
Notes / Conditions
THD+N, 1W
THD+N, 10W
THD+N, 60W
THD+N, 100W
THD+N, 200W
0.008%
0.003%
0.0015%
0.002%
0.009%
0.008%
0.004%
0.002%
0.004%
0.009%
1kHz, Single-channel riven
Dynamic Range 117 B 113 B A-weighte , AES-17 filter,
Single-channel operation
Resi ual Noise, 22Hz - 20kHzAES17 70µV
110µV
Self-oscillating – 400kHz
Damping Factor 2000 906 1kHz, relative to 8Ω loa
Channel Separation 92 B
90 B
72 B
92 B
80 B
62 B
100Hz
1kHz
10kHz
Frequency Response : 20Hz-20kHz
: 20Hz-35kHz
N/A ±0.25 B
±1 B 1W, 8Ω Loa
Thermal Performance Ty ical Notes / Conditions
I ling T
C
=30°C
T
PCB
=36°C
No signal input, T
A
=25°C
2ch x 31.25W (1/8 rate power) T
C
=54°C
T
PCB
=65°C
Continuous, T
A
=25°C
2ch x 250W (Rate power) T
C
=80°C
T
PCB
=106°C
At OTP shut own @ 150 sec,
T
A
=25°C
Physical S ecifications
Dimensions 7.76”(L) x 5.86”(W) x 2.2”(H)
192 mm (L) x 149mm (W) x56mm(H)
Weight 0.54kgm

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IRAUDAMP6 REV 1 .0
Connection Setu
Fig 1 Ty ical Test Setu
Volume
J7 J9
J1 J5
J3
R100
S1
S2
CH1 Out ut CH2 Out ut
CH1
In ut
CH2
In ut
G
Protection
Normal
S3
73.5V,8A DC supply
8~4 Ohm 8~4 Ohm
73.5V,8A DC supply
J6
Au io Signal Generator
J8
250W,Non-in uctive Resistors

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IRAUDAMP6 REV 1 .0
Connector Descri tion
CH1 IN J7 Analog input for CH1
CH2 IN J9 Analog input for CH2
POWER J3 Positive an negative supply (+B / -B)
CH1 OUT J1 Output for CH1
CH2 OUT J5 Output for CH2
EXT CLK J6 External clock sync
DCP OUT J8 DC protection relay output
Test Procedures
Test Setu :
1. Connect 8Ω-250 W ummy loa s to output connectors (J1 an J5 as shown on Fig 1) an
parallel it with input of Au io Precision analyzer (AP).
2. Connect the Au io Signal Generator to J7 an J9 for CH1 an CH2 respectively (AP).
3. Set up the ual power supply with voltages of ±73.5V;set current limit to 8A.
4. TURN OFF the ual power supply before connecting to ON of the unit un er test (UUT).
5. Set switch S1 to mi le position (self oscillating).
6. Set volume level knob R130 fully counter-clockwise (minimum volume).
7. Connect the ual power supply to J3. as shown on Fig 1
Power u :
8. Turn ON the ual power supply. The ±B supplies must be applie an remove at the
same time.
9. Re LED (Protection) shoul turn on almost imme iately an turn off after about 3s.
10. Green LED (Normal) then turns on after re LED is extinguishe an shoul stay on.
11. Quiescent current for the positive supply shoul be 84mA ±10mA at +73.5V.
12. Quiescent current for the negative supply shoul be 80mA ±10mA at –73.5V.
13. Push S3 switch(Trip an Reset push-buttom)to restart the sequence of LEDs
in icators,which shoul be the same as note above in steps 9-10.
Switching Frequency test
14. Monitor switching waveform at VS1/J4(pin9-12)of CH1 an VS2/J3(pin1-4)CH2 on
Daughter Boar using an Oscilloscope.
15. For IRAUDAMP6, the self-oscillating switching frequency is pre-calibrate to 400 KHz. To
mo ify the IRAUDAMP6 frequency, change the values of potentiometers R49 an R74 for
CH1 an CH2 respectively.

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IRAUDAMP6 REV 1 .0
Functionality Audio Tests:
16. Apply 1V RMS at 1kHz sinusoi al signal from the Au io Signal Generator.
17. Turn control volume up (R130 clock-wise) to obtain an output rea ing of 250Watts.
18. For all subsequent tests as shown on the Au io Precision graphs below (Fig 2- Fig7), the
measurements are taken across J1 an J5 with an AES-17 Filter. Observe that a 1 V
RMS
input generates an output voltage of 44.7 V
RMS
.
19. Sweep the au io signal voltage from 15 mV
RMS
to 1 V
RMS
.
20. Monitor the output signals at J1/J5 with an oscilloscope. The waveform must be a non
istorte sinusoi al signal.
Test Setu using Audio Precision (A ):
21. Use an unbalance -floating signal from the generator outputs.
22. Use balance inputs taken across output terminals, J1 an J5.
23. Connect Ap frame groun to GND at terminal J7/J9.
24. Select the AES-17 filter(pull- own menu) for all the testing except frequency response.
25. Sweep the input signal voltage from 15 mV
RMS
to 1 V
RMS
.
26. Run Ap test programs for all subsequent tests as shown in Fig 2- Fig 7below.
Performance and test gra hs
C o lo rS w e e p T ra c e L in e S t y l e T h i c k D a t a A x i s C o m m e n t
1 1 B l u e S o li 2 A n l r . T H D + N R a t io L e ft C H 2
1 3 R e S o li 2 A n l r . T H D + N R a t io L e ft C H 1
0.001
1 0
0.002
0.005
0 . 0 1
0 . 0 2
0 . 0 5
0 . 1
0 . 2
0 . 5
1
2
5
%
1 0 0 m 1 k2 0 0 m 5 0 0 m 1 2 5 1 0 2 0 5 0 1 0 0 2 0 0 5 0 0
W
±B Su ly = ±73.5V, 8 Ω Resistive Load
Fig 2 IRAUDAMP6, THD+N versus Power, Stereo, 8 Ω

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IRAUDAMP6 REV 1 .0
8 ohm loa
4 ohm loa
Fig 3 IRAUDAMP6, Frequency res onse

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IRAUDAMP6 REV 1 .0
.
ColorSweep Trace Line Style Thick Data Axis Comment
1 1 Re Soli 2 Anlr.THD+N Ratio Left 125W L
1 2 Blue Soli 2 Anlr.THD+N Ratio Left 125W R
2 1 Magenta Soli 2 Anlr.THD+N Ratio Left 25W L
2 2 Green Soli 1 Anlr.THD+N Ratio Left 25W R
0.0001
100
0.001
0.01
0.1
1
10
%
20 20k50 100 200 500 1k 2k 5k 10k
Hz
Fig 4 THD+N Ratio vs. Frequency

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IRAUDAMP6 REV 1 .0
ColorSweep Trace Line Style Thick Data Axis Comment
1 1 Magenta Soli 1 Fft.Ch.1 Ampl Left
1 2 Blue Soli 1 Fft.Ch.2 Ampl Left
-100
+0
-80
-60
-40
-20
B
V
10 20k20 50 100 200 500 1k 2k 5k 10k
Hz
Fig 5, 1V out ut Frequency S ectrum
ColorSweep Trace Line Style Thick Data Axis Comment
1 1 Re Soli 1 Fft.Ch.1 Ampl Left
1 2 Blue Soli 1 Fft.Ch.2 Ampl Left
-140
+20
-120
-100
-80
-60
-40
-20
+0
B
V
10 20k20 50 100 200 500 1k 2k 5k 10k
Hz
No signal, Self Oscillator @ 400kHz
Fig 6, IRAUDAMP6 Noise Floor