19-3678; Rev 2; 3/06
KIT
ATION
EVALU
BLE
AVAILA
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
General Description
The MAX9708 mono/stereo, Class D audio power amplifi-
er 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 amplifi-
er performance with the benefits of Class D efficiency,
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 configuration.
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.
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.
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.
Features
♦
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)
♦
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
♦
Available in Thermally Efficient, Space-Saving
Packages: 56-Pin TQFN and 64-Pin TQFP
MAX9708
Ordering Information
PART
MAX9708ETN+
MAX9708ECB*
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
56 TQFN-EP**
64 TQFP-EP**
PKG
CODE
T5688-3
C64E-6
Applications
LCD TVs
Automotive
PDP TVs
PC/HiFi Audio Solutions
Pin Configurations appear at end of data sheet.
+Denotes
lead-free package.
*Future
product—Contact factory for availability.
**EP
= Exposed paddle.
Simplified Block Diagram
FS1, FS2
SYNC
RIGHT
CHANNEL
LEFT
CHANNEL
MONO
2
2
MAX9708
SYNCOUT
FS1, FS2
SYNC
AUDIO
INPUT
2
MAX9708
SYNCOUT
CLASS D
MODULATOR
GAIN
CONTROL
OUTPUT
PROTECTION
CLASS D
MODULATOR
GAIN
CONTROL
2
3
TEMP
OUTPUT
PROTECTION
V
DIGITAL
MONO
3
TEMP
G1, G2
TH0, TH1,
TH2
G1, G2
TH0, TH1,
TH2
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
MAX9708
ABSOLUTE MAXIMUM RATINGS
PV
DD
, V
DD
to PGND, GND .......................................-0.3 to +30V
PV
DD
to V
DD
..........................................................-0.3V to +0.3V
OUTR+, OUTR-, OUTL+,
OUTL- to PGND, GND...........................-0.3V to (PV
DD
+ 0.3V)
C1N to GND .............................................-0.3V to (PV
DD
+ 0.3V)
C1P to GND..............................(PV
DD
- 0.3V) to (CPV
DD
+ 0.3V)
CPV
DD
to GND ..........................................(PV
DD
- 0.3V) to +40V
All Other Pins to GND.............................................-0.3V to +12V
Continuous Input Current (except PV
DD
, V
DD
, OUTR+,
OUTR-, OUTL+, and OUTL-) ...........................................20mA
Continuous Power Dissipation (T
A
= +70°C)
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
Thermal Resistance (θ
JC
)
56-Pin Thin QFN… .......................................................0.6°C/W
64-Pin TQFP….................................................................2°C/W
Lead Temperature (soldering, 10s) .................................+300°C
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
DD
= V
DD
= +18V, PGND = GND = 0V, C
SS
= 0.47µF, C
REG
= 0.01µF, C1 = 0.1µF, C2 = 1µF, R
LOAD
=
∞,
MONO = low (stereo
mode),
SHDN
=
MUTE
= high, G1 = low, G2 = high (A
V
= 22dB), FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (R
L
) are
connected between OUT_+ and OUT_-, unless otherwise stated. T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Supply Voltage Range
Shutdown Current
Shutdown to Full Operation
Mute to Full Operation
SYMBOL
V
DD
I
SHDN
t
SON
t
MUTE
G1 = 0, G2 = 1
Input Impedance
R
IN
G1 = 1, G2 = 1
G1 = 1, G2 = 0
G1= 0, G2 = 0
Output Pulldown Resistance
Output Offset Voltage
V
OS
SHDN
= GND
AC-coupled input, measured between
OUT_+ and OUT_-
PV
DD
= 10V to 18V
Power-Supply Rejection Ratio
PSRR
200mV
P-P
ripple
(Note 2)
DC, input referred
f = 20Hz to 20kHz, input referred
One power switch
FS1
0
Switching Frequency
f
SW
1
1
0
Oscillator Spread Bandwidth
SYNCIN Lock Range
Equal to f
SW
x 4
FS2
0
1 (SSM)
0
1
600
180
200
200
160
250
±2
1200
%
kHz
220
kHz
f
RIPPLE
= 1kHz
f
RIPPLE
= 20kHz
50
68
90
90
50
70
70
0.3
0.75
dB
Ω
dB
50
40
25
12
SHDN
= low
CONDITIONS
Inferred from PSRR test
MIN
10
0.1
100
100
85
63
43
21
600
±30
125
90
60
30
kΩ
mV
kΩ
TYP
MAX
18
1
UNITS
V
µA
ms
ms
Common-Mode Rejection Ratio
Switch On-Resistance
CMRR
R
DS
FS1 = FS2 = high (SSM)
2
_______________________________________________________________________________________
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
ELECTRICAL CHARACTERISTICS (continued)
(PV
DD
= V
DD
= +18V, PGND = GND = 0V, C
SS
= 0.47µF, C
REG
= 0.01µF, C1 = 0.1µF, C2 = 1µF, R
LOAD
=
∞,
MONO = low (stereo
mode),
SHDN
=
MUTE
= high, G1 = low, G2 = high (A
V
= 22dB), FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (R
L
) are
connected between OUT_+ and OUT_-, unless otherwise stated. T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
G1 = 0, G2 = 1
Gain
A
V
G1 = 1, G2 = 1
G1 = 1, G2 = 0
G1 = 0, G2 = 0
TH2
0
0
0
TEMP
Flag Threshold
T
FLAG
0
1
1
1
1
TEMP
Flag Accuracy
TEMP
Flag Hysteresis
STEREO MODE (R
LOAD
= 8Ω)
Quiescent Current
MUTE
= 1, R
LOAD
=
∞
MUTE
= 0
P
OUT
f = 1kHz, THD = 10%, T
A
= +25°C,
R
LOAD
= 8Ω, PV
DD
= 18V
f = 1kHz, BW = 22Hz to 22kHz,
R
LOAD
= 8Ω, P
OUT
= 8W
R
LOAD
= 8Ω, P
OUT
= 10W
22Hz to 22kHz
A-weighted
20
20
5
21
30
11
mA
TH1
0
0
1
1
0
0
1
1
TH0
0
1
0
1
0
1
0
1
+80
+90
+100
+110
+120
+129
+139
+150
±6
2
°C
°C
°C
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
dB
UNITS
MAX9708
From +80°C to +140°C
Output Power
W
Total Harmonic Distortion Plus
Noise
Signal-to-Noise Ratio
Efficiency
Left-Right Channel Gain
Matching
THD+N
SNR
η
0.1
91
96
87
0.02
%
dB
%
dB
R
LOAD
= 8Ω, L > 60µH, P
OUT
= 15W + 15W,
f = 1kHz
P
OUT
= 10W
_______________________________________________________________________________________
3
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
MAX9708
ELECTRICAL CHARACTERISTICS (continued)
(PV
DD
= V
DD
= +18V, PGND = GND = 0V, C
SS
= 0.47µF, C
REG
= 0.01µF, C1 = 0.1µF, C2 = 1µF, R
LOAD
=
∞,
MONO = low (stereo
mode),
SHDN
=
MUTE
= high, G1 = low, G2 = high (A
V
= 22dB), FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (R
L
) are
connected between OUT_+ and OUT_-, unless otherwise stated. T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Output Short-Circuit Current
Threshold
Click-and-Pop Level
SYMBOL
I
SC
R
LOAD
= 0Ω
Peak voltage, 32
samples/second,
A-weighted (Notes 2, 4)
MUTE
= 1, R
LOAD
=
∞
MUTE
= 0
P
OUT
f = 1kHz,
THD = 10%
R
LOAD
= 8Ω
R
LOAD
= 4Ω
Into shutdown
Out of shutdown
CONDITIONS
MIN
TYP
2.4
-63
dBV
-55
MAX
UNITS
A
K
CP
MONO MODE (R
LOAD
= 4Ω, MONO = High)
Quiescent Current
Output Power
Total Harmonic Distortion Plus
Noise
Signal-to-Noise Ratio
Efficiency
Output Short-Circuit Current
Threshold
Click-and-Pop Level
SNR
η
I
SC
20
5
23
42
0.12
91
95
85
4.8
Into shutdown
Out of shutdown
-60
dBV
-63
1
2.5
0.8
I
SINK
= 3mA
V
PULLUP
= 5.5V
0.2
0.4
µA
V
V
V
µA
mA
W
%
dB
%
A
f = 1kHz, BW = 22Hz to 22kHz,
R
LOAD
= 4Ω, P
OUT
= 17W
R
LOAD
= 4Ω,
P
OUT
= 10W
20Hz to 20kHz
A-weighted
R
LOAD
= 4Ω, L > 40µH, P
OUT
= 42W,
f = 1kHz
R
LOAD
= 0Ω
Peak voltage, 32
samples/second,
A-weighted (Notes 2, 4)
K
CP
DIGITAL INPUTS (SHDN,
MUTE,
G1, G2, FS1, FS2, TH0, TH1, TH2, SYNCIN, MONO)
Logic-Input Current
I
IN
0 to 12V
Logic-Input High Voltage
Logic-Input Low Voltage
Open-Drain Output Low Voltage
Leakage Current
V
IH
V
IL
V
OL
I
LEAK
OPEN-DRAIN OUTPUTS (TEMP, SYNCOUT)
Note 1:
Note 2:
Note 3:
Note 4:
All devices are 100% production tested at +25°C. All temperature limits are guaranteed by design.
Inputs AC-coupled to GND.
The device is current limited. The maximum output power is obtained with an 8Ω load.
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
MAX9708
Typical Operating Characteristics
(PV
DD
= V
DD
= +18V, PGND = GND = 0V, C
SS
= 0.47µF, C
REG
= 0.01µF, C1 = 0.1µF, C2 = 1µF, R
LOAD
=
∞,
SHDN
= high, MONO
= low,
MUTE
= high, G1 = low, G2 = high, FS1 = FS2 = high (SSM), SYNCIN = low. All load resistors (R
L
) are between OUT_+ and
OUT_-, T
A
= +25°C, unless otherwise stated.)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
MAX9708 toc01
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
MAX9708 toc02
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
PV
DD
= 18V,
8Ω STEREO MODE,
P
OUT
= 8.3W PER
CHANNEL
THD+N (%)
MAX9708 toc03
100
PV
DD
= 18V, 8Ω
STEREO MODE, 1kHz
10
THD+N (%)
100
PV
DD
= 12V,
STEREO MODE,
f
IN
= 1kHz
R
L
= 8Ω
1
1
10
THD+N (%)
1
0.1
0.1
0.1
R
L
= 4Ω
0.01
0
5
10
15
20
25
30
OUTPUT POWER PER CHANNEL (W)
0.01
0
5
10
15
OUTPUT POWER PER CHANNEL (W)
0.01
10
100
1k
FREQUENCY (Hz)
10k
100k
EFFICIENCY vs. OUTPUT POWER
MAX9708 toc04
OUTPUT POWER
vs. SUPPLY VOLTAGE
MAX9708 toc05
NO-LOAD SUPPLY CURRENT
vs. SUPPLY VOLTAGE
STEREO MODE
22
SUPPLY CURRENT (mA)
20
18
16
14
12
10
T
A
= -40°C
T
A
= +85°C
T
A
= +25°C
MAX9708 toc06
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
5
10
15
20
25
PV
DD
= 18V, 8Ω
STEREO MODE
30
OUTPUT POWER PER CHANNEL (W)
25
20
15
10
R
L
= 8Ω
STEREO MODE
24
10% THD+N
1% THD+N
5
0
30
10
12
14
SUPPLY VOLTAGE (V)
16
18
10
12
14
16
18
20
22
OUTPUT POWER PER CHANNEL (W)
SUPPLY VOLTAGE (V)
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX9708 toc07
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
PV
DD
= 18V, 4Ω MONO MODE,
1kHz
10
THD+N (%)
MAX9708 toc08
4.0
3.5
SUPPLY CURRENT (nA)
3.0
2.5
2.0
1.5
1.0
0.5
0
10
12
14
16
18
20
SHDN = 0
100
1
0.1
0.01
22
0
10
20
30
40
50
60
SUPPLY VOLTAGE (V)
OUTPUT POWER (W)
_______________________________________________________________________________________
5
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