MAX9708ECB [MAXIM]
20W/40W, Filterless, Spread-Spectrum, Mono/Stereo, Class D Amplifier; 20W / 40W ，无需滤波，扩频，单声道/立体声D类放大器
| 型号： | MAX9708ECB |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 20W/40W, Filterless, Spread-Spectrum, Mono/Stereo, Class D Amplifier |
| 文件： | 总24页 (文件大小：779K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-3678; Rev 0; 7/05
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
General Description
Features
The MAX9708 mono/stereo, Class D audio power ampli-
fier delivers up to 2 x 21W into an 8Ω stereo mode and
1 x 42W into a 4Ω load in mono mode while offering up
to 87% efficiency. The MAX9708 provides Class AB
amplifier performance with the benefits of Class D effi-
ciency, eliminating the need for a bulky heatsink and
conserving power. The MAX9708 operates from a single
+10V to +18V supply, driving the load in a BTL configu-
ration.
♦ 2 x 21W Output Power in Stereo Mode
(8Ω, THD = 10%)
♦ 1 x 42W Output Power in Mono Mode
(4Ω, THD = 10%)
♦ High Efficiency: Up to 87%
♦ Filterless Class D Amplifier
♦ Unique Patented Spread-Spectrum Mode
♦ Programmable Gain (+22dB, +25dB, +29.5dB,
+36dB)
The MAX9708 offers two modulation schemes: a fixed-
frequency modulation (FFM) mode, and a spread-spec-
trum modulation (SSM) mode that reduces
EMI-radiated emissions. The MAX9708 can be synchro-
nized to an external clock from 600kHz to 1.2MHz. A
synchronized output allows multiple units to be cascad-
ed in the system.
♦ High PSRR (90dB at 1kHz)
♦ Differential Inputs Suppress Common-Mode
Noise
♦ Shutdown and Mute Control
♦ Integrated Click-and-Pop Suppression
♦ Low 0.1% THD+N
♦ Current Limit and Thermal Protection
♦ Programmable Thermal Flag
♦ SYNC Input/Output
Features include fully differential inputs, comprehensive
click-and-pop suppression, and four selectable-gain set-
tings (22dB, 25dB, 29.5dB, and 36dB). A pin-program-
mable thermal flag provides seven different thermal
warning thresholds. Short-circuit and thermal-overload
protection prevent the device from being damaged
during a fault condition.
♦ Available in Thermally Efficient, Space-Saving
Packages: 56-Pin TQFN and 64-Pin TQFP
The MAX9708 is available in 56-pin TQFN (8mm x 8mm
x 0.8mm) and 64-pin TQFP (10mm x 10mm x 1.4mm)
packages, and is specified over the extended
-40°C to +85°C temperature range.
Ordering Information
PKG
PART
TEMP RANGE PIN-PACKAGE
CODE
MAX9708ETN
-40°C to +85°C 56 TQFN-EP**
T5688-3
C64E-6
Applications
PDP TVs
MAX9708ECB* -40°C to +85°C 64 TQFP-EP**
LCD TVs
*Future product—Contact factory for availability.
**EP = Exposed paddle.
Automotive
PC/HiFi Audio Solutions
Pin Configurations appear at end of data sheet.
Simplified Block Diagram
2
MAX9708
2
SYNCOUT
SYNCOUT
MAX9708
FS1, FS2
SYNC
FS1, FS2
SYNC
RIGHT
CHANNEL
AUDIO
INPUT
CLASS D
MODULATOR
CLASS D
MODULATOR
LEFT
CHANNEL
GAIN
V
DIGITAL
GAIN
CONTROL
OUTPUT
CONTROL
OUTPUT
PROTECTION
MONO
PROTECTION
MONO
G1, G2
2
2
G1, G2
3
3
TH0, TH1,
TH2
TH0, TH1,
TH2
TEMP
TEMP
STEREO MODE
MONO MODE
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
ABSOLUTE MAXIMUM RATINGS
PV , V
to PGND, GND.......................................-0.3 to +30V
Continuous Power Dissipation (T = +70°C)
A
DD DD
PV
to V ..........................................................-0.3V to +0.3V
56-Pin Thin QFN (derate 47.6mW/°C above +70°C) ......3.81W
64-Pin TQFP (derate 43.5mW/°C above +70°C).............3.48W
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Junction Temperature......................................................+150°C
DD
DD
OUTR+, OUTR-, OUTL+,
OUTL- to PGND, GND...........................-0.3V to (PV
C1N to GND .............................................-0.3V to (PV
+ 0.3V)
+ 0.3V)
+ 0.3V)
DD
DD
DD
C1P to GND..............................(PV
- 0.3V) to (CPV
DD
CPV to GND ..........................................(PV - 0.3V) to +40V
All Other Pins to GND.............................................-0.3V to +12V
Thermal Resistance (θ
)
DD
DD
JC
56-Pin Thin QFN… .......................................................0.6°C/W
64-Pin TQFP….................................................................2°C/W
Lead Temperature (soldering, 10s) .................................+300°C
Continuous Input Current (except PV , V , OUTR+,
DD DD
OUTR-, OUTL+, and OUTL-) ...........................................20mA
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(PV
= V
= +18V, PGND = GND = 0V, C = 0.47µF, C
= 0.01µF, C1 = 0.1µF, C2 = 1µF, R
= ∞, MONO = low (stereo
DD
DD
SS
REG
LOAD
mode), SHDN = MUTE = high, G1 = low, G2 = high (A = 22dB), FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (R ) are
V
L
connected between OUT_+ and OUT_-, unless otherwise stated. T = T
to T
, unless otherwise noted. Typical values are at T
A
MIN
MAX
A
= +25°C.) (Note 1)
PARAMETER
Supply Voltage Range
Shutdown Current
SYMBOL
CONDITIONS
Inferred from PSRR test
MIN
TYP
MAX
18
UNITS
V
10
V
DD
I
t
SHDN = low
0.1
100
100
85
1
µA
ms
ms
SHDN
Shutdown to Full Operation
Mute to Full Operation
t
SON
MUTE
G1 = 0, G2 = 1
G1 = 1, G2 = 1
G1 = 1, G2 = 0
G1= 0, G2 = 0
SHDN = GND
50
40
25
12
125
90
63
Input Impedance
R
kΩ
IN
43
60
21
30
Output Pulldown Resistance
Output Offset Voltage
600
kΩ
AC-coupled input, measured between
OUT_+ and OUT_-
V
30
mV
OS
PV
= 10V to 18V
68
50
90
90
50
70
70
0.3
DD
Power-Supply Rejection Ratio
PSRR
dB
f
f
= 1kHz
RIPPLE
RIPPLE
200mV
(Note 2)
ripple
P-P
= 20kHz
DC, input referred
Common-Mode Rejection Ratio
Switch On-Resistance
CMRR
dB
f = 20Hz to 20kHz, input referred
One power switch
R
0.75
220
Ω
DS
FS1
0
FS2
0
180
600
200
200
160
250
2
Switching Frequency
f
1
1 (SSM)
kHz
SW
1
0
1
0
Oscillator Spread Bandwidth
SYNCIN Lock Range
FS1 = FS2 = high (SSM)
Equal to f x 4
%
1200
kHz
SW
2
_______________________________________________________________________________________
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
ELECTRICAL CHARACTERISTICS (continued)
(PV
= V
= +18V, PGND = GND = 0V, C = 0.47µF, C
= 0.01µF, C1 = 0.1µF, C2 = 1µF, R
= ∞, MONO = low (stereo
DD
DD
SS
REG
LOAD
mode), SHDN = MUTE = high, G1 = low, G2 = high (A = 22dB), FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (R ) are
V
L
connected between OUT_+ and OUT_-, unless otherwise stated. T = T
to T
, unless otherwise noted. Typical values are at T
A
MIN
MAX
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
21.6
24.9
29.2
35.9
TYP
22.0
25.0
29.5
36.0
MAX
22.3
25.6
29.9
36.6
UNITS
G1 = 0, G2 = 1
G1 = 1, G2 = 1
Gain
A
dB
V
G1 = 1, G2 = 0
G1 = 0, G2 = 0
TH2
0
TH1
0
TH0
0
+80
+90
0
0
1
0
1
0
+100
+110
+120
+129
+139
+150
TEMP Flag Threshold
T
0
1
1
°C
FLAG
1
0
0
1
0
1
1
1
0
1
1
1
TEMP Flag Accuracy
TEMP Flag Hysteresis
From +80°C to +140°C
6
°C
°C
2
STEREO MODE (R
= 8Ω)
LOAD
MUTE = 1, R
MUTE = 0
= ∞
20
5
30
11
LOAD
Quiescent Current
mA
W
f = 1kHz, THD = 10%, T = +25°C,
A
Output Power
P
20
21
OUT
R
= 8Ω, PV = 18V
DD
LOAD
Total Harmonic Distortion Plus
Noise
f = 1kHz, BW = 22Hz to 22kHz,
THD+N
SNR
η
0.1
%
dB
%
R
= 8Ω, P
= 8W
LOAD
OUT
22Hz to 22kHz
A-weighted
91
96
Signal-to-Noise Ratio
Efficiency
R
= 8Ω, P
= 10W
LOAD
OUT
R
= 8Ω, L > 60µH, P
= 15W + 15W,
LOAD
OUT
87
f = 1kHz
Left-Right Channel Gain
Matching
P
= 10W
0.02
dB
OUT
_______________________________________________________________________________________
3
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
ELECTRICAL CHARACTERISTICS (continued)
(PV
= V
= +18V, PGND = GND = 0V, C = 0.47µF, C
= 0.01µF, C1 = 0.1µF, C2 = 1µF, R
= ∞, MONO = low (stereo
DD
DD
SS
REG
LOAD
mode), SHDN = MUTE = high, G1 = low, G2 = high (A = 22dB), FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (R ) are
V
L
connected between OUT_+ and OUT_-, unless otherwise stated. T = T
to T
, unless otherwise noted. Typical values are at T
A
MIN
MAX
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Output Short-Circuit Current
Threshold
I
R
= 0Ω
LOAD
2.4
A
SC
Peak voltage, 32
samples/second,
A-weighted (Notes 2, 4)
Into shutdown
-63
-55
Click-and-Pop Level
K
CP
dBV
Out of shutdown
MONO MODE (R
= 4Ω, MONO = High)
LOAD
MUTE = 1, R
MUTE = 0
= ∞
20
5
LOAD
Quiescent Current
Output Power
mA
W
R
R
= 8Ω
23
42
LOAD
LOAD
f = 1kHz,
THD = 10%
P
OUT
= 4Ω
Total Harmonic Distortion Plus
Noise
f = 1kHz, BW = 22Hz to 22kHz,
0.12
%
R
LOAD
= 4Ω, P = 17W
OUT
20Hz to 20kHz
A-weighted
91
95
R
= 4Ω,
= 10W
LOAD
Signal-to-Noise Ratio
Efficiency
SNR
dB
%
P
OUT
R
LOAD
= 4Ω, L > 40µH, P
= 42W,
OUT
η
85
f = 1kHz
Output Short-Circuit Current
Threshold
I
R
= 0Ω
4.8
A
SC
LOAD
Peak voltage, 32
samples/second,
A-weighted (Notes 2, 4)
Into shutdown
-60
-63
Click-and-Pop Level
K
CP
dBV
Out of shutdown
DIGITAL INPUTS (SHDN, MUTE, G1, G2, FS1, FS2, TH0, TH1, TH2, SYNCIN, MONO)
Logic-Input Current
I
0 to 12V
1
µA
V
IN
Logic-Input High Voltage
Logic-Input Low Voltage
V
2.5
IH
V
0.8
0.4
V
IL
OPEN-DRAIN OUTPUTS (TEMP, SYNCOUT)
Open-Drain Output Low Voltage
Leakage Current
V
I
= 3mA
SINK
V
OL
I
V
= 5.5V
PULLUP
0.2
µA
LEAK
Note 1: All devices are 100% production tested at +25°C. All temperature limits are guaranteed by design.
Note 2: Inputs AC-coupled to GND.
Note 3: The device is current limited. The maximum output power is obtained with an 8Ω load.
Note 4: Testing performed with an 8Ω resistive load in series with a 68µH inductive load connected across BTL outputs. Mode tran-
sitions are controlled by SHDN.
4
_______________________________________________________________________________________
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Typical Operating Characteristics
(PV
= V
= +18V, PGND = GND = 0V, C = 0.47µF, C
= 0.01µF, C1 = 0.1µF, C2 = 1µF, R
= ∞, SHDN = high, MONO
DD
DD
SS
REG
LOAD
= low, MUTE = high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (R ) are between OUT_+ and
L
OUT_-, T = +25°C, unless otherwise stated.)
A
TOTAL HARMONIC DISTORTION PLUS NOISE
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
100
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
1
vs. OUTPUT POWER
100
PV = 18V, 8Ω
PV = 12V,
DD
STEREO MODE,
PV = 18V,
DD
DD
STEREO MODE, 1kHz
8Ω STEREO MODE,
f
= 1kHz
P
= 8.3W PER
OUT
IN
10
1
10
CHANNEL
R = 8Ω
L
1
0.1
0.1
R = 4Ω
L
0.1
0.01
0.01
0.01
0
5
10
15
0
5
10
15
20
25
30
10
100
1k
10k
100k
OUTPUT POWER PER CHANNEL (W)
OUTPUT POWER PER CHANNEL (W)
FREQUENCY (Hz)
OUTPUT POWER
vs. SUPPLY VOLTAGE
NO-LOAD SUPPLY CURRENT
vs. SUPPLY VOLTAGE
EFFICIENCY vs. OUTPUT POWER
30
25
20
15
10
5
24
22
20
18
16
14
12
10
100
90
80
70
60
50
40
30
20
10
R = 8Ω
L
STEREO MODE
STEREO MODE
T
= +25°C
A
T
A
= +85°C
10% THD+N
T
A
= -40°C
1% THD+N
PV = 18V, 8Ω
DD
STEREO MODE
0
10
12
14
SUPPLY VOLTAGE (V)
16
18
10
12
14
16
18
20
22
0
5
10
15
20
25
30
SUPPLY VOLTAGE (V)
OUTPUT POWER PER CHANNEL (W)
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
100
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
PV = 18V, 4Ω MONO MODE,
DD
SHDN = 0
1kHz
10
1
0.1
0.01
0
10
20
30
40
50
60
10
12
14
16
18
20
22
OUTPUT POWER (W)
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
5
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Typical Operating Characteristics (continued)
(PV
= V
= +18V, PGND = GND = 0V, C = 0.47µF, C
= 0.01µF, C1 = 0.1µF, C2 = 1µF, R
= ∞, SHDN = high, MONO
DD
DD
SS
REG
LOAD
= low, MUTE = high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (R ) are between OUT_+ and
L
OUT_-, T = +25°C, unless otherwise stated.)
A
TOTAL HARMONIC DISTORTION PLUS NOISE
WIDEBAND OUTPUT SPECTRUM
(SSM MODE)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
vs. OUTPUT POWER
100
30
20
1
PV = 12V,
DD
MONO MODE,
PV = 18V,
DD
10kHz RBW
4Ω MONO MODE,
f
= 1kHz
10
P
= 18W
OUT
IN
L
10
1
R = 4Ω
0
-10
-20
-30
-40
-50
-60
-70
0.1
0.1
0.01
0.01
0
5
10
15
20
25
100k
1M
10M
100M
10
100
1k
10k
100k
OUTPUT POWER (W)
FREQUENCY (Hz)
FREQUENCY (Hz)
WIDEBAND OUTPUT SPECTRUM
(FFM MODE)
OUTPUT FREQUENCY SPECTRUM
(FFM MODE)
OUTPUT FREQUENCY SPECTRUM
(SSM MODE)
30
20
0
-20
0
-20
10kHz RBW
10
0
-40
-40
-10
-20
-30
-40
-50
-60
-70
-60
-60
-80
-80
-100
-120
-100
-120
100k
1M
10M
100M
0
4
8
12
16
20
24
0
4
8
12
16
20
24
FREQUENCY (Hz)
FREQUENCY (kHz)
FREQUENCY (kHz)
6
_______________________________________________________________________________________
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Typical Operating Characteristics (continued)
(PV
= V
= +18V, PGND = GND = 0V, C = 0.47µF, C
= 0.01µF, C1 = 0.1µF, C2 = 1µF, R
= ∞, SHDN = high, MONO
DD
DD
SS
REG
LOAD
= low, MUTE = high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (R ) are between OUT_+ and
L
OUT_-, T = +25°C, unless otherwise stated.)
A
OUTPUT POWER
vs. LOAD RESISTANCE
OUTPUT POWER
vs. SUPPLY VOLTAGE
EFFICIENCY vs. OUTPUT POWER
100
60
50
40
30
20
10
0
60
50
40
30
20
10
0
MONO MODE,
10% THD+N,
PV = 18V
DD
R = 4Ω,
L
90
80
70
60
50
40
30
MONO MODE,
10% THD+N
PV = 18V,
DD
4Ω MONO MODE
20
10
0
10
20
30
40
50
60
10
12
14
SUPPLY VOLTAGE (V)
16
18
4
6
8
10
12
OUTPUT POWER (W)
LOAD RESISTANCE (Ω)
OUTPUT POWER
vs. LOAD RESISTANCE
MUTE RESPONSE
SHUTDOWN RESPONSE
MAX9708 toc19
MAX9708 toc20
30
25
20
15
10
5
STEREO MODE,
10% THD+N,
PV = 18V
DD
SHDN
5V/div
MUTE
5V/div
OUTPUT
50mV/div
OUTPUT
50mV/div
0
7
8
9
10
11
12
40ms/div
40ms/div
LOAD RESISTANCE (Ω)
_______________________________________________________________________________________
7
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Typical Operating Characteristics (continued)
(PV
= V
= +18V, PGND = GND = 0V, C = 0.47µF, C
= 0.01µF, C1 = 0.1µF, C2 = 1µF, R
= ∞, SHDN = high, MONO
DD
DD
SS
REG
LOAD
= low, MUTE = high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (R ) are between OUT_+ and
L
OUT_-, T = +25°C, unless otherwise stated.)
A
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
COMMON-MODE REJECTION RATIO
CROSSTALK vs. FREQUENCY
vs. FREQUENCY
-40
-50
-30
-40
-60
INPUT REFERRED
-65
-70
-75
-60
-50
-70
-60
-80
-80
-70
-85
-90
-90
-80
-95
-100
-110
-120
-90
-100
-105
-110
-100
-110
10
100
1k
10k
100k
10
100
1k
10k
100k
10
100
1k
10k
100k
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
MAXIMUM STEADY-STATE OUTPUT POWER
vs. TEMPERATURE
MAXIMUM STEADY-STATE OUTPUT POWER
vs. TEMPERATURE
40
70
PV = 18V, 8Ω
DD
PV = 18V, 4Ω
DD
35
30
25
20
15
10
5
STEREO MODE, 1kHz,
FS1 = FS2 = 1
TH0 = TH1 = 1
TH2 = 0
60
50
40
30
MONO MODE, 1kHz,
FS1 = FS2 = 1
TH0 = TH1 = 1
TH2 = 0
20
10
MEASURED WITH THE EV KIT (TQFN
PACKAGE), JUNCTION TEMPERATURE
MAINTAINED AT +110°C
MEASURED WITH THE EV KIT (TQFN
PACKAGE), JUNCTION TEMPERATURE
MAINTAINED AT +110°C
0
0
50
30
40
60
70
60
AMBIENT TEMPERATURE (°C)
30
40
50
70
AMBIENT TEMPERATURE (°C)
Pin Description
PIN
NAME
FUNCTION
TQFP
TQFN
1, 8, 13, 16,
17, 32, 33, 41, 1, 12, 42, 43,
N.C.
No Connection. Not internally connected.
Power Ground
44, 55, 56
48, 49, 50, 55,
58, 63, 64
2, 3, 4, 45, 46,
47, 56, 57
2, 3, 4, 39,
40, 41, 49, 50
PGND
5, 6, 7,
42, 43, 44
5, 6, 7,
36, 37, 38
Positive Power Supply. Bypass to PGND with a 0.1µF and a 47µF capacitor with the
smallest capacitor placed as close to pins as possible.
PV
DD
8
_______________________________________________________________________________________
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Pin Description (continued)
PIN
NAME
FUNCTION
TQFP
9
TQFN
8
9
C1N
C1P
Charge-Pump Flying Capacitor C1, Negative Terminal
Charge-Pump Flying Capacitor C1, Positive Terminal
10
Charge-Pump Power Supply. Bypass to PV
as possible.
with a 1µF capacitor as close to the pin
DD
11
12
14
10
11
13
CPV
DD
SYNCOUT Open-Drain, Slew-Rate Limited Clock Output. Pullup with a 10kΩ resistor to REG.
Clock Synchronization Input. Allows for synchronization of the internal oscillator with an
SYNCIN
external clock. SYNCIN is internally pulled up to V
with a 100kΩ resistor.
REG
15
18
19
20
14
15
16
17
FS2
FS1
Frequency Select 2
Frequency Select 1
INL-
INL+
Left-Channel Negative Input (Stereo Mode Only)
Left-Channel Positive Input (Stereo Mode Only)
Mono/Stereo Mode Input. Drive logic-high for mono mode. Drive logic-low for stereo
mode.
21
18
MONO
22, 23, 24
25, 26
27
19, 20, 21
22, 23
24
REG
GND
SS
Internal Regulator Output Voltage (6V). Bypass with a 0.01µF capacitor to GND.
Analog Ground
Soft-Start. Connect a 0.47µF capacitor to GND to utilize soft-start power-up sequence.
Analog Power Supply. Bypass to GND with a 0.1µF capacitor as close to pin as
possible.
28
25
V
DD
29
30
31
34
26
27
28
29
INR-
INR+
G1
Right-Channel Positive Input. In mono mode, INR+ is the positive input.
Right-Channel Negative Input. In mono mode, INR- is the negative input.
Gain Select Input 1
G2
Gain Select Input 2
Active-Low Shutdown Input. Drive SHDN high for normal operation. Drive SHDN low to
place the device in shutdown mode.
35
30
SHDN
MUTE
Active-Low Mute Input. Drive logic-low to place the device in mute. In mute mode,
Class D output stage is no longer switching. Drive high for normal operation. MUTE is
36
31
internally pulled up to V
with a 100kΩ resistor.
REG
37
38
32
33
TEMP
TH2
Thermal Flag Output, Open Drain. Pull up with a 10kΩ resistor to REG.
Temperature Flag Threshold Select Input 2
Temperature Flag Threshold Select Input 1
Temperature Flag Threshold Select Input 0
Right-Channel Negative Output
39
34
TH1
40
35
TH0
51, 52
53, 54
59, 60
61, 62
EP
45, 46
47, 48
51, 52
53, 54
EP
OUTR-
OUTR+
OUTL-
OUTL+
EP
Right-Channel Positive Output
Left-Channel Negative Output
Left-Channel Positive Output
Exposed Paddle. Connect to GND with multiple vias for best heat dissipation.
_______________________________________________________________________________________
9
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Typical Application Circuits/Functional Diagrams
V
DD
PV
DD
0.1µF
47µF*
V
DIGITAL
22, 23
(25, 26)
5–7, 36–38
(5–7, 42-44)
2–4, 39–41 49–50
(2–4, 45–47, 56–57)
25 (28)
V
DIGITAL
GND
V
DD
PV
DD
PGND
10kΩ
15 (18)
FS1
11 (12)
SYNCOUT
14 (15) FS2
CONTROL
13 (14)
SYNCIN
R
F
MAX9708
PV
DD
V
BIAS
1µF
R
R
IN
17 (20)
16 (19)
INL+
INL-
+
-
OUTL+ 53, 54 (61, 62)
OUTL- 51, 52 (59, 60)
CLASS D
MODULATOR
AND H-BRIDGE
LEFT
CHANNEL
1µF
IN
R
F
R
F
PV
DD
1µF
1µF
R
R
IN
27 (30)
26 (29)
INR+
INR-
+
47, 48 (53, 54)
OUTR+
CLASS D
MODULATOR
AND H-BRIDGE
RIGHT
CHANNEL
MUX
OUTR- 45, 46 (51, 52)
IN
-
C2
1µF
V
BIAS
CPV
10 (11)
C1P 9 (10)
C1N
DD
PV
DD
30 (35)
31 (36)
V
DIGITAL
SHDN
R
MUTE
G2
F
C1
0.1µF
CHARGE
PUMP
28 (31)
29 (34)
8 (9)
GAIN
CONTROL
G1
REG 19, 20, 21 (22, 23, 24)
18 (21)
MONO
REGULATOR
C
REG
0.01µF
TEMP 32 (37)
THERMAL SENSOR
10kΩ
SS
TH0
34 (39)
TH1
TH2
35 (40)
33 (38)
24 (27)
C
SS
V
DIGITAL
0.47µF
V
DIGITAL
CONFIGURATION: TQFN STEREO MODE, SSM, INTERNAL OSCILLATOR, GAIN = 22dB, THERMAL SETTING = +120°C
( ) TQFP PACKAGE
*ADDITIONAL BULK CAPACITANCE
Figure 1. Typical Application and Functional Diagram in Stereo Mode
10 ______________________________________________________________________________________
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Typical Application Circuits/Functional Diagrams (continued)
V
DD
PV
DD
47µF*
0.1µF
0.1µF
V
DIGITAL
22, 23
5–7, 36–38
(5–7, 42–44)
2–4, 39–41 49–50
(2–4, 45–47, 56–57)
(25, 26)
25 (28)
V
DIGITAL
GND
V
DD
PV
DD
PGND
10kΩ
FS1
FS2
15 (18)
11 (12)
SYNCOUT
14 (15)
CONTROL
R
13 (14)
SYNCIN
F
MAX9708
PV
DD
V
BIAS
1µF
R
R
IN
17 (20)
16 (19)
INR+
INR-
+
-
OUTL+ 53, 54 (61, 62)
OUTL- 51, 52 (59, 60)
CLASS D
MODULATOR
AND H-BRIDGE
AUDIO
INPUT
1µF
IN
PV
DD
R
F
47, 48 (53, 54)
OUTR+
CLASS D
MODULATOR
AND H-BRIDGE
MUX
OUTR- 45, 46 (51, 52)
C2
1µF
CPV
10 (11)
C1P 9 (10)
C1N
DD
PV
30 (35)
31 (36)
28 (31)
DD
SHDN
V
V
DIGITAL
MUTE
G1
C1
0.1µF
CHARGE
PUMP
8 (9)
GAIN
CONTROL
29 (34)
18 (21)
G2
REG 19, 20, 21 (22, 23, 24)
MONO
REGULATOR
DIGITAL
C
REG
0.01µF
32 (37)
TEMP
THERMAL SENSOR
10kΩ
SS
TH0
34 (39)
TH1
TH2
35 (40)
33 (38)
24 (27)
C
SS
V
DIGITAL
0.47µF
V
DIGITAL
CONFIGURATION: TQFN MONO MODE, SSM, INTERNAL OSCILLATOR, GAIN = 22dB, THERMAL SETTING = +120°C
( ) TQFP PACKAGE
*ADDITIONAL BULK CAPACITANCE
Figure 2. Typical Application and Functional Diagram in Mono Mode
______________________________________________________________________________________ 11
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
powers. Under normal operating levels (typical music
Detailed Description
reproduction levels), efficiency falls below 30%, where-
as the MAX9708 still exhibits 87% efficiency under the
same conditions.
The MAX9708 filterless, Class D audio power amplifier
features several improvements to switch-mode amplifi-
er technology. The MAX9708 is a two-channel, stereo
amplifier with 21W output power on each channel. The
amplifier can be configured to output 42W output
power in mono mode. The device offers Class AB per-
formance with Class D efficiency, while occupying min-
imal board space. A unique filterless modulation
scheme and spread-spectrum switching mode create a
compact, flexible, low-noise, efficient audio power
amplifier. The differential input architecture reduces
common-mode noise pickup, and can be used without
input-coupling capacitors. The device can also be con-
figured as a single-ended input amplifier.
Shutdown
The MAX9708 features a shutdown mode that reduces
power consumption and extends battery life. Driving
SHDN low places the device in low-power (0.1µA) shut-
down mode. Connect SHDN to digital high for normal
operation.
Mute Function
The MAX9708 features a clickless/popless mute mode.
When the device is muted, the outputs stop switching,
muting the speaker. Mute only affects the output stage
and does not shut down the device. To mute the
MAX9708, drive MUTE to logic-low. Driving MUTE low
during the power-up/down or shutdown/turn-on cycle
optimizes click-and-pop suppression.
Mono/Stereo Configuration
The MAX9708 features a mono mode that allows the
right and left channels to operate in parallel, achieving
up to 42W of output power. The mono mode is enabled
by applying logic-high to MONO. In this mode, an
audio signal applied to the right channel (INR+/INR-) is
routed to the H-bridge of both channels, while a signal
applied to the left channel (INL+/INL-) is ignored.
OUTL+ must be connected to OUTR+ and OUTL- must
be connected to OUTR- using heavy PC board traces
as close to the device as possible (see Figure 2).
Click-and-Pop Suppression
The MAX9708 features comprehensive click-and-pop
suppression that eliminates audible transients on start-
up and shutdown. While in shutdown, the H-bridge is
pulled to GND through a 330kΩ resistor. During startup
or power-up, the input amplifiers are muted and an
internal loop sets the modulator bias voltages to the
correct levels, preventing clicks and pops when the H-
bridge is subsequently enabled. Following startup, a
soft-start function gradually un-mutes the input ampli-
fiers. The value of the soft-start capacitor has an impact
on the click-and-pop levels as well as startup time.
When the device is placed in mono mode on a PC
board with outputs wired together, ensure that the
MONO pin can never be driven low when the device is
enabled. Driving the MONO pin low (stereo mode)
while the outputs are wired together in mono mode may
trigger the short circuit or thermal protection or both,
and may even damage the device.
Thermal Sensor
The MAX9708 features an on-chip temperature sensor
that monitors the die temperature. When the junction
temperature exceeds a programmed level, TEMP is
pulled low. This flags the user to reduce power or shut
down the device. TEMP may be connected to SS or
MUTE for automatic shutdown during overheating. If
TEMP is connected to MUTE, during thermal-protection
mode, the audio is muted and the device is in mute
mode. If TEMP is connected to SS, during thermal-pro-
tection mode, the device is shut down but the thermal
sensor is still active.
Efficiency
Efficiency of a Class D amplifier is attributed to the
region of operation of the output stage transistors. In a
Class D amplifier, the output transistors act as current-
steering switches and consume negligible additional
power. Any power loss associated with the Class D out-
put stage is mostly due to the I2R loss of the MOSFET
on-resistance and quiescent current overhead. The
theoretical best efficiency of a linear amplifier is 78%;
however, that efficiency is only exhibited at peak output
12 ______________________________________________________________________________________
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Operating Modes
TEMP returns high once the junction temperature cools
below the set threshold minus the thermal hysteresis. If
TEMP is connected to either MUTE or SS, the audio
output resumes. The temperature threshold is set by
the TH0, TH1, and TH2 inputs as shown in Table 1. An
RC filter may be used to eliminate any transient at the
TEMP output as shown in Figure 3.
Fixed-Frequency Modulation (FFM) Mode
The MAX9708 features three switching frequencies in
the FFM mode (Table 3). In this mode, the frequency
spectrum of the Class D output consists of the funda-
mental switching frequency and its associated harmon-
ics (see the Wideband Output Spectrum graph in the
Typical Operating Characteristics). Select one of the
three fixed switching frequencies such that the harmon-
ics do not fall in a sensitive band. The switching fre-
quency can be changed at any time without affecting
audio reproduction.
Gain Selection
The MAX9708 features four pin-selectable gain settings;
see Table 2.
Spread-Spectrum Modulation (SSM) Mode
The MAX9708 features a unique, patented spread-
spectrum (SSM) mode that flattens the wideband spec-
tral components, improving EMI emissions that may be
radiated by the speaker and cables. This mode is
enabled by setting FS1 = FS2 = high. In SSM mode, the
switching frequency varies randomly by 4% around
the center frequency (200kHz). The modulation scheme
remains the same, but the period of the triangle wave-
form changes from cycle to cycle. Instead of a large
amount of spectral energy present at multiples of the
switching frequency, the energy is now spread over a
bandwidth that increases with frequency. Above a few
megahertz, the wideband spectrum looks like white
noise for EMI purposes. SSM mode reduces EMI com-
pared to fixed-frequency mode. This can also help to
randomize visual artifacts caused by radiated or sup-
ply-borne interference in displays.
V
DIGITAL
10kΩ
10kΩ
TO DIGITAL
INPUT
TEMP
0.1µF
Figure 3. An RC Filter Eliminates Transient During Switching
Table 1. MAX9708 Junction Temperature
Threshold Setting
JUNCTION
Synchronous Switching Mode
The MAX9708 SYNCIN input allows the Class D amplifi-
er to switch at a frequency defined by an external clock
frequency. Synchronizing the amplifier with an external
clock source may confine the switching frequency to a
less sensitive band. The external clock frequency range
is from 600kHz to 1.2MHz and can have any duty cycle,
but the minimum pulse must be greater than 100ns.
TEMPERATURE
(°C)
TH2
TH1
TH0
80
Low
Low
Low
Low
High
High
High
High
Low
Low
High
High
Low
Low
High
High
Low
High
Low
High
Low
High
Low
High
90
100
110
120
129
139
150
SYNCOUT is an open-drain clock output for synchro-
nizing external circuitry. Its frequency is four times the
amplifier’s switching frequency, and it is active in either
internal or external oscillator mode.
Table 3. Switching Frequencies
Table 2. MAX9708 Gain Setting
SYNCOUT
FS1
FS2
MODULATION
FREQUENCY (kHz)
G1
G2
GAIN (dB)
Low
High
High
Low
High
High
Low
Low
22
25
0
0
1
1
0
1
0
1
200
250
160
Fixed-Frequency
Fixed-Frequency
Fixed-Frequency
Spread-Spectrum
29.5
36
200
4
______________________________________________________________________________________ 13
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Linear Regulator (REG)
The supply voltage range for the MAX9708 is from 10V
1µF
to 18V to achieve high-output power. An internal linear
INR+
regulator reduces this voltage to 6.3V for use with
small-signal and digital circuitry that does not require a
high-voltage supply. Bypass a 0.01µF capacitor from
REG to GND.
MAX9708
Applications Information
INR-
Logic Inputs
All of the digital logic inputs and output have an
absolute maximum rating of +12V. If the MAX9708 is
operating with a supply voltage between 10V and 12V,
1µF
digital inputs can be connected to PV
or V . If
DD
DD
Figure 4. Single-Ended Input Connections
PV
and V
are greater than 12V, digital inputs and
DD
DD
outputs must connected to a digital system supply
lower than 12V.
Choose C so that f
is well below the lowest fre-
-3dB
IN
quency of interest. Setting f
too high affects the
-3dB
Input Amplifier
low-frequency response of the amplifier. Use capaci-
tors with dielectrics that have low-voltage coefficients,
such as tantalum or aluminum electrolytic. Capacitors
with high-voltage coefficients, such as ceramics, may
result in increased distortion at low frequencies.
Differential Input
The MAX9708 features a differential input structure,
making them compatible with many CODECs, and
offering improved noise immunity over a single-ended
input amplifier. In devices such as flat-panel displays,
noisy digital signals can be picked up by the amplifier’s
inputs. These signals appear at the amplifiers’ inputs as
common-mode noise. A differential input amplifier
amplifies only the difference of the two inputs, while any
signal common to both inputs is attenuated.
Output Filter
The MAX9708 does not require an output filter.
However, output filtering can be used if a design is fail-
ing radiated emissions due to board layout or cable
length, or the circuit is near EMI-sensitive devices.
Refer to the MAX9708 Evaluation Kit for suggested filter
topologies. The tuning and component selection of the
filter should be optimized for the load. A purely resistor
load (8Ω) used for lab testing will require different com-
ponents than a real, complex load-speaker load.
Single-Ended Input
The MAX9708 can be configured as a single-ended
input amplifier by capacitively coupling either input to
GND and driving the other input (Figure 4).
Charge-Pump Capacitor Selection
The MAX9708 has an internal charge-pump converter
that produces a voltage level for internal circuitry. It
requires a flying capacitor (C1) and a holding capacitor
(C2). Use capacitors with an ESR less than 100mΩ for
optimum performance. Low-ESR ceramic capacitors
minimize the output resistance of the charge pump. For
best performance over the extended temperature
range, select capacitors with an X7R dielectric. The
capacitors’ voltage rating must be greater than 36V.
Component Selection
Input Filter
An input capacitor, C , in conjunction with the input
IN
impedance of the MAX9708, forms a highpass filter that
removes the DC bias from an incoming signal. The AC-
coupling capacitor allows the amplifier to bias the signal
to an optimum DC level. Assuming zero-source imped-
ance, the -3dB point of the highpass filter is given by:
1
f−3dB
=
2π R
C
IN IN
14 ______________________________________________________________________________________
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Continuous Sine Wave vs. Music
When a Class D amplifier is evaluated in the lab, often
a continuous sine wave is used as the signal source.
While this is convenient for measurement purposes, it
represents a worst-case scenario for thermal loading
on the amplifier. It is not uncommon for a Class D
amplifier to enter thermal shutdown if driven near maxi-
mum output power with a continuous sine wave. The
PC board must be optimized for best dissipation (see
the PC Board Thermal Considerations section).
Sharing Input Sources
In certain systems, a single audio source can be
shared by multiple devices (speaker and headphone
amplifiers). When sharing inputs, it is common to mute
the unused device, rather than completely shutting it
down, preventing the unused device inputs from dis-
torting the input signal. Mute the MAX9708 by driving
MUTE low. Driving MUTE low turns off the Class D out-
put stage, but does not affect the input bias levels of
the MAX9708.
Audio content, both music and voice, has a much lower
RMS value relative to its peak output power. Therefore,
while an audio signal may reach similar peaks as a
continuous sine wave, the actual thermal impact on the
Class D amplifier is highly reduced. If the thermal per-
formance of a system is being evaluated, it is important
to use actual audio signals instead of sine waves for
testing. If sine waves must be used, the thermal perfor-
mance will be less than the system’s actual capability
for real music or voice.
Frequency Synchronization
The MAX9708 outputs up to 21W on each channel in
stereo mode. If higher output power or a 2.1 solution is
needed, two MAX9708s can be used. Each MAX9708
is synchronized by connecting SYNCOUT from the first
MAX9708 to SYNCIN of the second MAX9708 (see
Figure 5).
Supply Bypassing/Layout
Proper power-supply bypassing ensures low-distortion
operation. For optimum performance, bypass PV
to
DD
DD
PC Board Thermal Considerations
The exposed pad is the primary route for conducting
heat away from the IC. With a bottom-side exposed
pad, the PC board and its copper becomes the primary
heatsink for the Class D amplifier. Solder the exposed
pad to a copper polygon. Add as much copper as pos-
sible from this polygon to any adjacent pin on the Class
D amplifier as well as to any adjacent components, pro-
vided these connections are at the same potential.
These copper paths must be as wide as possible. Each
of these paths contributes to the overall thermal capa-
bilities of the system.
PGND with a 0.1µF capacitor as close to each PV
pin as possible. A low-impedance, high-current power-
supply connection to PV is assumed. Additional bulk
DD
capacitance should be added as required depending
on the application and power-supply characteristics.
GND and PGND should be star-connected to system
ground. For the TQFN package, solder the exposed
paddle (EP) to the ground plane using multiple-plated
through-hole vias. The exposed paddle must be sol-
dered to the ground plane for rated power dissipation
and good ground return. Use wider PC board traces to
lower the parasitic resistance for the high-power output
pins (OUTR+, OUTR-, OUTL+, OUTL-). Refer to the
MAX9708 Evaluation Kit for layout guidance.
The copper polygon to which the exposed pad is
attached should have multiple vias to the opposite side
of the PC board, where they connect to another copper
polygon. Make this polygon as large as possible within
the system’s constraints for signal routing.
Thermal Considerations
Class D amplifiers provide much better efficiency and
thermal performance than a comparable Class AB
amplifier. However, the system’s thermal performance
must be considered with realistic expectations along
with its many parameters.
Additional improvements are possible if all the traces
from the device are made as wide as possible.
Although the IC pins are not the primary thermal path
out of the package, they do provide a small amount.
The total improvement would not exceed approximately
10%, but it could make the difference between accept-
able performance and thermal problems.
______________________________________________________________________________________ 15
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Auxiliary Heatsinking
If operating in higher ambient temperatures, it is possible
to improve the thermal performance of a PC board with
the addition of an external heatsink. The thermal resis-
tance to this heatsink must be kept as low as possible to
maximize its performance. With a bottom-side exposed
pad, the lowest resistance thermal path is on the bottom
of the PC board. The topside of the IC is not a significant
thermal path for the device, and therefore is not a cost-
effective location for a heatsink. If an LC filter is used in
the design, placing the inductor in close proximity to the
IC can help draw heat away from the MAX9708.
Another consideration is the load impedance across
the audio frequency band. A loudspeaker is a complex
electro-mechanical system with a variety of resonance.
In other words, an 8Ω speaker usually has 8Ω imped-
ance within a very narrow range. This often extends
well below 8Ω, reducing the thermal efficiency below
what is expected. This lower-than-expected impedance
can be further reduced when a crossover network is
used in a multidriver audio system.
Systems Application Circuit
The MAX9708 can be configured into multiple amplifier
systems. One concept is a 2.1 audio system (Figure 5)
where a stereo audio source is split into three channels.
The left- and right-channel inputs are highpass filtered
to remove the bass content, and then amplified by the
MAX9708 in stereo mode. Also, the left- and right-chan-
nel inputs are summed together and lowpass filtered to
remove the high-frequency content, then amplified by a
second MAX9708 in mono mode.
Thermal Calculations
The die temperature of a Class D amplifier can be esti-
mated with some basic calculations. For example, the
die temperature is calculated for the below conditions:
• T = +40°C
A
• P
= 16W
OUT
• Efficiency (η) = 87%
The conceptual drawing of Figure 5 can be applied to
either single-ended or differential systems. Figure 6
illustrates the circuitry required to implement a fully
differential filtering system. By maintaining a fully differ-
ential path, the signal-to-noise ratio remains uncompro-
mised and noise pickup is kept very low. However,
keeping a fully differential signal path results in almost
twice the component count, and therefore performance
must be weighed against cost and size.
• θ = 21°C/W
JA
First, the Class D amplifier’s power dissipation must be
calculated:
P
16W
OUT
η
0.87 −16W = 2.4W
P
=
− P =
OUT
DISS
Then the power dissipation is used to calculate the die
temperature, T , as follows:
The highpass and lowpass filters should have different
cutoff frequencies to ensure an equal power response
at the crossover frequency. The filters should be at
-6dB amplitude at the crossover frequency, which is
known as a Linkwitz-Riley alignment. In the example
circuit of Figure 6, the -3dB cutoff frequency for the
highpass filters is 250Hz, and the -3dB cutoff frequency
for the lowpass filter is 160Hz. Both the highpass filters
and the lowpass filters are at a -6dB amplitude at
approximately 200Hz. If the filters were to have the
same -3dB cutoff frequency, a measurement of sound
pressure level (SPL) vs. frequency would have a peak
at the crossover frequency.
C
T = T +P
× θ = 40°C + 24W × 21°C/ W = 90.4°C
C
A
DISS
JA
Load Impedance
The on-resistance of the MOSFET output stage in Class
D amplifiers affects both the efficiency and the peak-cur-
rent capability. Reducing the peak current into the load
reduces the I2R losses in the MOSFETs, which increases
efficiency. To keep the peak currents lower, choose the
highest impedance speaker that can still deliver the
desired output power within the voltage swing limits of
the Class D amplifier and its supply voltage.
The circuit in Figure 6 uses inverting amplifiers for their
ease in biasing. Note the phase labeling at the outputs
has been reversed. The resistors should be 1% or better
in tolerance and the capacitors 5% tolerance or better.
Although most loudspeakers fall either 4Ω or 8Ω, there
are other impedances available that can provide a
more thermally efficient solution.
16 ______________________________________________________________________________________
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Mismatch in the components can cause discrepancies
The left and right drivers should be at an 8Ω to 12Ω
impedance, whereas the subwoofer can be 4Ω to 12Ω
depending on the desired output power, the available
power-supply voltage, and the sensitivity of the individ-
ual speakers in the system. The four gain settings of
the MAX9708 allow gain adjustments to match the sen-
sitivity of the speakers.
between the nominal transfer function and actual perfor-
mance. Also, the mismatch of the input resistors (R15,
R17, R19, and R21 in Figure 6) of the summing amplifier
and lowpass filter will cause some high-frequency sound
to be sent to the subwoofer.
The circuit in Figure 6 drives a pair of MAX9708 devices
similar to the circuit in Figure 5. The inputs to the
MAX9708 still require AC-coupling to prevent compro-
mising the click-and-pop performance of the MAX9708.
8Ω
INR+
INR-
RIGHT
AUDIO
HIGHPASS
FILTER
OUTR+
OUTR-
FULL-
RANGE
SPEAKER
MONO
MAX9708
8Ω
INL+
INL-
HIGHPASS
FILTER
LEFT
AUDIO
OUTL+
OUTL-
FULL-
RANGE
SPEAKER
SYNCOUT
SYNCIN
4Ω OR 8Ω
WOOFER
INR+
INR-
OUTR+
OUTR-
LOWPASS
FILTER
Σ
MAX9708
V
DIGITAL
MONO
INL+
OUTL+
OUTL-
INL-
Figure 5. Multiple Amplifiers Implement a 2.1 Audio System
______________________________________________________________________________________ 17
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
R1
56.2kΩ
R2, 56.2kΩ
C1
C2
R3
28kΩ
47nF
47nF
2
3
U1A
1
MAX4478
R4
28kΩ
RIGHT
AUDIO
INPUT
BIAS
R5
56.2kΩ
RIGHT
AUDIO
OUTPUT
R6, 56.2kΩ
C3
47nF
C4
47nF
R7
28kΩ
6
5
U1B
7
MAX4478
BIAS
R8
56.2kΩ
RIGHT AND LEFT OUTPUTS
ARE AC-COUPLED TO A
MAX9708 CONFIGURED AS
A STEREO AMPLIFIER
R9, 56.2kΩ
C5
47nF
C6
47nF
R10
28kΩ
9
U1C
8
MAX4478
R11
28kΩ
10
LEFT
AUDIO
INPUT
BIAS
R12
56.2kΩ
LEFT
AUDIO
OUTPUT
R13, 56.2kΩ
C7
47nF
C8
47nF
R14
28kΩ
13
12
U1D
14
MAX4478
R15
R16
BIAS
BIAS
BIAS
26.1kΩ
13kΩ
SUBWOOFER OUTPUT IS
AC-COUPLED TO A
MAX9708 CONFIGURED AS
A MONO AMPLIFIER
C9, 47nF
R17
26.1kΩ
R18
7.5kΩ
2
3
U2A
1
C10
47nF
MAX4478
R19
26.1kΩ
R20
13kΩ
SUBWOOFER
AUDIO
OUTPUT
C11, 47nF
R21
28kΩ
R22
7.5kΩ
6
5
U2B
7
MAX4478
NOTE:
OP-AMP POWER PINS OMITTED FOR CLARITY.
ALL RESISTORS ARE 1% OR BETTER.
ALL CAPACITORS ARE 5% OR BETTER.
Figure 6. Fully Differential Crossover Filters
18 ______________________________________________________________________________________
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Pin Configurations
TOP VIEW
42 41 40 39 38 37 36 35
34 33 32 31 30 29
N.C. 43
44
28 G1
N.C.
27 INR+
OUTR- 45
OUTR- 46
OUTR+ 47
OUTR+ 48
PGND 49
26 INR-
25
V
DD
24 SS
23 GND
22 GND
PGND 50
OUTL- 51
OUTL- 52
21 REG
20 REG
19 REG
MAX9708
MONO
OUTL+ 53
OUTL+ 54
18
17 INL+
N.C. 55
N.C. 56
16 INL-
15
FS1
1
2
3
4
5
6
7
8
9
10 11 12 13 14
THIN QFN
______________________________________________________________________________________ 19
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Pin Configurations (continued)
TOP VIEW
64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49
N.C.
PGND
PGND
PGND
1
2
3
4
5
6
7
8
9
48 N.C.
47 PGND
46 PGND
45 PGND
PV
DD
PV
DD
PV
DD
44 PV
43 PV
42 PV
DD
DD
DD
N.C.
C1N
41 N.C.
40 TH0
39 TH1
38 TH2
37 TEMP
36 MUTE
35 SHDN
34 G2
MAX9708
C1P 10
CPV 11
DD
SYNCOUT 12
N.C. 13
SYNCIN 14
FS2 15
N.C. 16
33 N.C.
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
TQFP
Chip Information
PROCESS: BiCMOS
20 ______________________________________________________________________________________
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages.)
______________________________________________________________________________________ 21
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages.)
22 ______________________________________________________________________________________
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages.)
PACKAGE OUTLINE,
64L TQFP, 10x10x1.4mm
1
21-0083
B
2
______________________________________________________________________________________ 23
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages.)
PACKAGE OUTLINE,
64L TQFP, 10x10x1.4mm
2
21-0083
B
2
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
24 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2005 Maxim Integrated Products
Freed
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
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