General Description
The MAX9708 mono/stereo, Class D audio power ampli-
fier delivers up to 2 x 21W into an 8
stereo mode and
1 x 42W into a 4
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.
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
-40C to +85C temperature range.
Applications
LCD TVs
PDP TVs
Automotive
PC/HiFi Audio Solutions
Features
2 x 21W Output Power in Stereo Mode
(8
, THD = 10%)
1 x 42W Output Power in Mono Mode
(4
, 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
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
________________________________________________________________ Maxim Integrated Products
1
CLASS D
MODULATOR
SYNCOUT
TEMP
OUTPUT
PROTECTION
GAIN
CONTROL
FS1, FS2
MAX9708
STEREO MODE
G1, G2
2
SYNC
RIGHT
CHANNEL
LEFT
CHANNEL
MONO
2
TH0, TH1,
TH2
3
PART
TEMP RANGE
PIN-PACKAGE
PKG
CODE
MAX9708ETN
-40C to +85C
56 TQFN-EP**
T5688-3
MAX9708ECB*
-40C to +85C
64 TQFP-EP**
C64E-6
Simplified Block Diagram
Ordering Information
19-3678; Rev 0; 7/05
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.
*Future product--Contact factory for availability.
**EP = Exposed paddle.
Pin Configurations appear at end of data sheet.
EVALUATION KIT
AVAILABLE
CLASS D
MODULATOR
SYNCOUT
TEMP
OUTPUT
PROTECTION
GAIN
CONTROL
FS1, FS2
MAX9708
MONO MODE
G1, G2
2
SYNC
AUDIO
INPUT
V
DIGITAL
MONO
2
TH0, TH1,
TH2
3
MAX9708
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(PV
DD
= V
DD
= +18V, PGND = GND = 0V, C
SS
= 0.47F, C
REG
= 0.01F, C1 = 0.1F, C2 = 1F, 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
= +25C.) (Note 1)
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.
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
= +70C)
56-Pin Thin QFN (derate 47.6mW/C above +70C) ......3.81W
64-Pin TQFP (derate 43.5mW/C above +70C).............3.48W
Operating Temperature Range ...........................-40C to +85C
Storage Temperature Range .............................-65C to +150C
Junction Temperature ......................................................+150C
Thermal Resistance (
JC
)
56-Pin Thin QFN... .......................................................0.6C/W
64-Pin TQFP....................................................................2C/W
Lead Temperature (soldering, 10s) .................................+300C
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Voltage Range
V
DD
Inferred from PSRR test
10
18
V
Shutdown Current
I
SHDN
SHDN = low
0.1
1
A
Shutdown to Full Operation
t
SON
100
ms
Mute to Full Operation
t
MUTE
100
ms
G1 = 0, G2 = 1
50
85
125
G1 = 1, G2 = 1
40
63
90
G1 = 1, G2 = 0
25
43
60
Input Impedance
R
IN
G1= 0, G2 = 0
12
21
30
k
Output Pulldown Resistance
SHDN = GND
600
k
Output Offset Voltage
V
OS
AC-coupled input, measured between
OUT_+ and OUT_-
30
mV
PV
DD
= 10V to 18V
68
90
f
RIPPLE
= 1kHz
90
Power-Supply Rejection Ratio
PSRR
200mV
P-P
ripple
(Note 2)
f
RIPPLE
= 20kHz
50
dB
DC, input referred
50
70
Common-Mode Rejection Ratio
CMRR
f = 20Hz to 20kHz, input referred
70
dB
Switch On-Resistance
R
DS
One power switch
0.3
0.75
FS1
FS2
0
0
180
200
220
1
1 (SSM)
200
1
0
160
Switching Frequency
f
SW
0
1
250
kHz
Oscillator Spread Bandwidth
FS1 = FS2 = high (SSM)
2
%
SYNCIN Lock Range
Equal to f
SW
x 4
600
1200
kHz
MAX9708
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
_______________________________________________________________________________________
3
ELECTRICAL CHARACTERISTICS (continued)
(PV
DD
= V
DD
= +18V, PGND = GND = 0V, C
SS
= 0.47F, C
REG
= 0.01F, C1 = 0.1F, C2 = 1F, 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
= +25C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
G1 = 0, G2 = 1
21.6
22.0
22.3
G1 = 1, G2 = 1
24.9
25.0
25.6
G1 = 1, G2 = 0
29.2
29.5
29.9
Gain
A
V
G1 = 0, G2 = 0
35.9
36.0
36.6
dB
TH2
TH1
TH0
0
0
0
+80
0
0
1
+90
0
1
0
+100
0
1
1
+110
1
0
0
+120
1
0
1
+129
1
1
0
+139
TEMP Flag Threshold
T
FLAG
1
1
1
+150
C
TEMP Flag Accuracy
From +80C to +140C
6
C
TEMP Flag Hysteresis
2
C
STEREO MODE (R
LOAD
= 8
)
MUTE = 1, R
LOAD
=
20
30
Quiescent Current
MUTE = 0
5
11
mA
Output Power
P
OUT
f = 1kHz, THD = 10%, T
A
= +25C,
R
LOAD
= 8
, PV
DD
= 18V
20
21
W
Total Harmonic Distortion Plus
Noise
THD+N
f = 1kHz, BW = 22Hz to 22kHz,
R
LOAD
= 8
, P
OUT
= 8W
0.1
%
22Hz to 22kHz
91
Signal-to-Noise Ratio
SNR
R
LOAD
= 8
, P
OUT
= 10W
A-weighted
96
dB
Efficiency
R
LOAD
= 8
, L > 60H , P
OU T
= 15W + 15W ,
f = 1kHz
87
%
Left-Right Channel Gain
Matching
P
OUT
= 10W
0.02
dB
MAX9708
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
4
_______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(PV
DD
= V
DD
= +18V, PGND = GND = 0V, C
SS
= 0.47F, C
REG
= 0.01F, C1 = 0.1F, C2 = 1F, 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
= +25C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Output Short-Circuit Current
Threshold
I
SC
R
LOAD
= 0
2.4
A
Into shutdown
-63
Click-and-Pop Level
K
CP
Peak voltage, 32
samples/second,
A-weighted (Notes 2, 4)
Out of shutdown
-55
dBV
MONO MODE (R
LOAD
= 4
, MONO = High)
MUTE = 1, R
LOAD
=
20
Quiescent Current
MUTE = 0
5
mA
R
LOAD
= 8
23
Output Power
P
OUT
f = 1kHz,
THD = 10%
R
LOAD
= 4
42
W
Total Harmonic Distortion Plus
Noise
f = 1kHz, BW = 22Hz to 22kHz,
R
LOAD
= 4
, P
OUT
= 17W
0.12
%
20Hz to 20kHz
91
Signal-to-Noise Ratio
SNR
R
LOAD
= 4
,
P
OUT
= 10W
A-weighted
95
dB
Efficiency
R
LOAD
= 4
, L > 40H, P
OUT
= 42W,
f = 1kHz
85
%
Output Short-Circuit Current
Threshold
I
SC
R
LOAD
= 0
4.8
A
Into shutdown
-60
Click-and-Pop Level
K
CP
Peak voltage, 32
samples/second,
A-weighted (Notes 2, 4)
Out of shutdown
-63
dBV
DIGITAL INPUTS (SHDN, MUTE, G1, G2, FS1, FS2, TH0, TH1, TH2, SYNCIN, MONO)
Logic-Input Current
I
IN
0 to 12V
1
A
Logic-Input High Voltage
V
IH
2.5
V
Logic-Input Low Voltage
V
IL
0.8
V
OPEN-DRAIN OUTPUTS (TEMP, SYNCOUT)
Open-Drain Output Low Voltage
V
OL
I
SINK
= 3mA
0.4
V
Leakage Current
I
LEAK
V
PULLUP
= 5.5V
0.2
A
Note 1: All devices are 100% production tested at +25C. 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 8
load.
Note 4: Testing performed with an 8
resistive load in series with a 68H inductive load connected across BTL outputs. Mode tran-
sitions are controlled by SHDN.
MAX9708
20W/40W, Filterless, Spread-Spectrum,
Mono/Stereo, Class D Amplifier
_______________________________________________________________________________________
5
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
MAX9708 toc01
OUTPUT POWER PER CHANNEL (W)
THD+N (%)
25
20
15
10
5
0.1
1
10
100
0.01
0
30
PV
DD
= 18V, 8
STEREO MODE, 1kHz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
MAX9708 toc02
OUTPUT POWER PER CHANNEL (W)
THD+N (%)
10
5
0.1
1
10
100
0.01
0
15
PV
DD
= 12V,
STEREO MODE,
f
IN
= 1kHz
R
L
= 8
R
L
= 4
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX9708 toc03
FREQUENCY (Hz)
THD+N (%)
10k
1k
100
0.1
10
100k
1
0.01
PV
DD
= 18V,
8
STEREO MODE,
P
OUT
= 8.3W PER
CHANNEL
EFFICIENCY vs. OUTPUT POWER
MAX9708 toc04
OUTPUT POWER PER CHANNEL (W)
EFFICIENCY (%)
25
20
15
10
5
20
30
40
50
60
70
80
90
100
10
0
30
PV
DD
= 18V, 8
STEREO MODE
OUTPUT POWER
vs. SUPPLY VOLTAGE
MAX9708 toc05
SUPPLY VOLTAGE (V)
OUTPUT POWER PER CHANNEL (W)
16
14
12
5
10
15
20
25
30
0
10
18
R
L
= 8
STEREO MODE
10% THD+N
1% THD+N
NO-LOAD SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX9708 toc06
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
20
18
16
14
12
12
14
16
18
20
22
24
10
10
22
STEREO MODE
T
A
= +25
C
T
A
= +85
C
T
A
= -40
C
Typical Operating Characteristics
(PV
DD
= V
DD
= +18V, PGND = GND = 0V, C
SS
= 0.47F, C
REG
= 0.01F, C1 = 0.1F, C2 = 1F, 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
= +25C, unless otherwise stated.)
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX9708 toc07
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (nA)
20
18
12
14
16
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0
10
22
SHDN = 0
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
MAX9708 toc08
OUTPUT POWER (W)
THD+N (%)
50
40
30
20
10
0.1
1
10
100
0.01
0
60
PV
DD
= 18V, 4
MONO MODE,
1kHz
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