MAX9703_V01 [MAXIM]
10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers;
| 型号： | MAX9703_V01 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 10W Stereo/15W Mono, Filterless, Spread-Spectrum, Class D Amplifiers |
| 文件： | 总24页 (文件大小：1931K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
General Description
Features
● Filterless Class D Amplifier
The MAX9703/MAX9704 mono/stereo Class D audio
power amplifiers provide Class AB amplifier performance
with Class D efficiency, conserving board space and
eliminating the need for a bulky heatsink. Using a Class
D architecture, these devices deliver up to 15W while
offering up to 78% efficiency. Proprietary and protected
modulation and switching schemes render the traditional
Class D output filter unnecessary.
● Unique Spread-Spectrum Mode Offers 5dB
Emissions Improvement Over Conventional Methods
● Up to 78% Efficient (R = 8Ω)
L
● Up to 88% Efficient (R = 16Ω)
L
● 15W Continuous Output Power into 8Ω (MAX9703)
● 2x10W Continuous Output Power into 8Ω (MAX9704)
● Low 0.07% THD+N
The MAX9703/MAX9704 offer two modulation schemes:
a fixed-frequency mode (FFM), and a spread-spectrum
mode (SSM) that reduces EMI-radiated emissions due
to the modulation frequency. The device utilizes a fully
differential architecture, a full bridged output, and compre-
hensive click-and-pop suppression.
● High PSRR (80dB at 1kHz)
● 10V to 25V Single-Supply Operation
● Differential Inputs Minimize Common-Mode Noise
● Pin-Selectable Gain Reduces Component Count
● Industry-Leading Click-and-Pop Suppression
● Low Quiescent Current (24mA)
The MAX9703/MAX9704 feature high 80dB PSRR, low
0.07% THD+N, and SNR in excess of 95dB. Short-circuit
and thermal-overload protection prevent the devices from
being damaged during a fault condition. The MAX9703 is
available in a 32-pin TQFN (5mm x 5mm x 0.8mm) pack-
age. The MAX9704 is available in a 32-pin TQFN (7mm x
7mm x 0.8mm) package. Both devices are specified over
the extended -40°C to +85°C temperature range.
● Low-Power Shutdown Mode (0.2μA)
● Short-Circuit and Thermal-Overload Protection
● Available in Thermally Efficient, Space-Saving
Packages
• 32-Pin TQFN (5mm x 5mm x 0.8mm)–MAX9703
• 32-Pin TQFN (7mm x 7mm x 0.8mm)–MAX9704
Ordering Information
Applications
● LCD TVs
● LCD Monitors
● Desktop PCs
● LCD Projectors
PART
PIN-PACKAGE
32 TQFN-EP*
32 TQFN-EP*
AMP
Mono
Stereo
PKG CODE
T3255-4
● Hands-Free Car Phone
MAX9703ETJ+
MAX9704ETJ+
Adapters
T3277-2
Note: All devices specified for over -40°C to +85°C operating
temperature range.
*EP = Exposed paddle.
+Denotes lead-free package.
Block Diagrams
0.47µF
MAX9704
INL+
INL-
OUTL+
OUTL-
MAX9703
H-BRIDGE
H-BRIDGE
0.47µF
0.47µF
IN+
OUT+
H-BRIDGE
0.47µF
IN-
0.47µF
0.47µF
OUT-
INR+
OUTR+
OUTR-
INR-
Pin Configurations appears at end of data sheet.
19-3160; Rev 8; 5/14
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Absolute Maximum Ratings
(All voltages referenced to PGND.)
Continuous Power Dissipation (T = +70°C)
A
V
to PGND, AGND............................................................30V
Single-Layer Board:
DD
OUTR_, OUTL_, C1N.................................-0.3V to (V
+ 0.3V)
MAX9703 32-Pin TQFN (derate 21.3mW/°C
DD
C1P............................................(V
CHOLD........................................................(V
- 0.3V) to (CHOLD + 0.3V)
above +70°C)..........................................................1702.1mW
MAX9704 32-Pin TQFN (derate 27mW/°C
DD
- 0.3V) to +40V
DD
All Other Pins to PGND...........................................-0.3V to +12V
Duration of OUTR_/OUTL_
above +70°C)..........................................................2162.2mW
Multilayer Board:
Short Circuit to PGND, V ................................................10s
MAX9703 32-Pin TQFN (derate 34.5mW/°C
DD
Continuous Input Current (V , PGND) ...............................1.6A
Continuous Input Current......................................................0.8A
Continuous Input Current (all other pins)..........................±20mA
above +70°C)..........................................................2758.6mW
MAX9704 32-Pin TQFN (derate 37mW/°C
DD
above +70°C)..........................................................2963.0mW
Junction Temperature......................................................+150°C
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
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
(V
= 15V, AGND = PGND = 0V, SHDN ≥ V , A = 16dB, C = C = 0.47μF, C
= 0.01μF, C1 = 100nF, C2 = 1μF, FS1 = FS2
REG
DD
IH
V
SS
IN
= PGND (f = 660kHz), R connected between OUTL+ and OUTL- and OUTR+ and OUTR-, T = T
to T
, unless otherwise
S
L
A
MIN
MAX
noted. Typical values are at T = +25°C.) (Notes 1, 2)
A
PARAMETER
GENERAL
SYMBOL
CONDITIONS
Inferred from PSRR test
MIN
TYP
MAX
UNITS
Supply Voltage Range
Quiescent Current
Shutdown Current
Turn-On Time
V
10
25
22
34
1.5
V
DD
MAX9703
MAX9704
14
24
I
R = OPEN
mA
µA
ms
DD
L
I
0.2
100
50
SHDN
C
C
= 470nF
= 180nF
SS
t
ON
SS
Amplifier Output Resistance in
Shutdown
SHDN = PGND
150
330
kΩ
kΩ
A
A
A
A
= 13dB
35
30
58
48
80
65
V
V
V
V
= 16dB
Input Impedance
Voltage Gain
R
IN
= 19.1dB
= 29.6dB
23
39
55
10
15
22
G1 = L, G2 = L
G1 = L, G2 = H
G1 = H, G2 = L
G1 = H, G2 = H
29.4
18.9
12.8
15.9
29.6
19.1
13
29.8
19.3
13.2
16.3
A
dB
V
16
Gain Matching
Between channels (MAX9704)
0.5
±6
%
mV
dB
Output Offset Voltage
Common-Mode Rejection Ratio
V
±30
OS
CMRR
f
= 1kHz, input referred
60
IN
V
= 10V to 25V
54
80
DD
Power-Supply Rejection Ratio
(Note 3)
f
f
= 1kHz
80
PSRR
dB
RIPPLE
200mV
ripple
P-P
= 20kHz
66
RIPPLE
Maxim Integrated
│ 2
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Electrical Characteristics (continued)
(V
= 15V, AGND = PGND = 0V, SHDN ≥ V , A = 16dB, C = C = 0.47μF, C
= 0.01μF, C1 = 100nF, C2 = 1μF, FS1 = FS2
REG
DD
IH
V
SS
IN
= PGND (f = 660kHz), R connected between OUTL+ and OUTL- and OUTR+ and OUTR-, T = T
to T
, unless otherwise
S
L
A
MIN
MAX
noted. Typical values are at T = +25°C.) (Notes 1, 2)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
R = 4Ω
10
15
THD+N = 10%, V
= 16V, f = 1kHz, T =
L
DD
Continuous Output Power
(MAX9703)
A
P
R = 8Ω
W
CONT
CONT
L
+25°C, t
(Note 4)
= 15min
CONT
R = 16Ω, V
= 24V
= 24V
18
L
DD
R = 4Ω
2x5
2x10
2x16
THD+N = 10%, V
= 16V, f = 1kHz, T =
L
DD
Continuous Output Power
(MAX9704)
A
P
R = 8Ω
W
%
L
+25°C, t
(Note 4)
= 15min
CONT
R = 16Ω, V
L
DD
Total Harmonic Distortion Plus
Noise
f
P
= 1kHz, either FFM or SSM, R = 8Ω,
IN L
THD+N
SNR
0.07
= 4W
OUT
FFM
94
88
BW = 22Hz to
22kHz
SSM
FFM
SSM
R = 8Ω, P
10W, f = 1kHz
=
L
OUT
Signal-to-Noise Ratio
Crosstalk
dB
dB
97
A-weighted
91
Left to right, right to left, 8Ω load, f = 10kHz
65
IN
FS1 = L, FS2 = L
FS1 = L, FS2 = H
FS1 = H, FS2 = L
560
670
940
470
800
Oscillator Frequency
f
kHz
OSC
670
±7%
FS1 = H, FS2 = H (spread-spectrum mode)
P
P
= 15W, f = 1kHz, R = 8Ω
78
88
6
OUT
OUT
L
Efficiency
η
%
V
= 10W, f = 1kHz, R = 16Ω
L
Regulator Output
V
REG
DIGITAL INPUTS (SHDN, FS_, G_)
V
2.5
IH
Input Thresholds
V
V
0.8
±1
IL
Input Leakage Current
µA
Note 1: All devices are 100% production tested at +25°C. All temperature limits are guaranteed by design.
Note 2: Testing performed with a resistive load in series with an inductor to simulate an actual speaker load. For R = 8Ω, L = 68μH.
L
For R = 4Ω, L = 33μH.
L
Note 3: PSRR is specified with the amplifier inputs connected to AGND through C
.
IN
Note 4: The MAX9704 continuous 8Ω and 16Ω power measurements account for thermal limitations of the 32-pin TQFN-EP pack-
age. Continuous 4Ω power measurements account for short-circuit protection of the MAX9703/MAX9704 devices.
Maxim Integrated
│ 3
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Typical Operating Characteristics
(33μH with 4Ω, 68μH with 8Ω, part in SSM mode, 136μH with 16Ω, measurement BW = 22Hz to 22kHz, unless otherwise noted.)
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
10
1
10
1
10
1
V
= 15V
V
= 15V
V
= 20V
DD
DD
DD
R = 4Ω
R = 8Ω
R = 8Ω
A = 16dB
V
L
L
L
A
= 16dB
A
= 16dB
V
V
P
OUT
= 8W
P
OUT
= 8W
P
OUT
= 4W
0.1
0.01
0.1
0.01
0.1
0.01
P
= 500mW
OUT
P
= 500mW
1k
OUT
P
= 500mW
OUT
10
100
10k
100k
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
FREQUENCY (Hz)
10k
100k
FREQUENCY (Hz)
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
10
1
100
10
1
10
1
V
= 20V
V
R
A
= 15V
= 4Ω
= 16dB
DD
DD
V
= 15V
DD
R = 8Ω
L
L
R = 8Ω
L
A
P
= 16dB
= 8W
V
V
A
= 16dB
V
OUT
f = 10kHz
SSM
f = 10kHz
f = 1kHz
0.1
0.1
0.01
0.1
FFM
f = 1kHz
f = 100Hz
f = 100Hz
0.01
0.01
3
4
5
10
100
1k
FREQUENCY (Hz)
10k
100k
0
1
2
6
7
8
9
10
9
0
1
2
3
4
5
6
7
8
10 11 12 13 14 15
OUTPUT POWER (W)
OUTPUT POWER (W)
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. OUTPUT POWER
EFFICIENCY vs. OUTPUT POWER
100
10
10
1
100
90
80
70
60
50
40
30
20
10
0
V = 20V
DD
V
= 20V
DD
R = 8Ω
L
R = 8Ω
R = 8Ω
L
L
A = 16dB
A
= 16dB
V
V
f = 10kHz
f = 1kHz
SSM
1
R = 4Ω
L
f = 1kHz
0.1
0.1
V
A
= 12V
= 16dB
DD
FFM (335kHz)
V
f = 100Hz
f = 1kHz
0.01
0.01
2
9
0
4
6
8
10 12 14 16 18 20
0 1 2 3 4 5 6 7 8 9 1011 12 131415 161718 19 20
OUTPUT POWER (W)
0
2
3
4
5
6
7
8
10
1
OUTPUT POWER (W)
OUTPUT POWER (W)
Maxim Integrated
│
4
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Typical Operating Characteristics (continued)
(33μH with 4Ω, 68μH with 8Ω, part in SSM mode, 136μH with 16Ω, measurement BW = 22Hz to 22kHz, unless otherwise noted.)
OUTPUT POWER
OUTPUT POWER
EFFICIENCY vs. OUTPUT POWER
vs. SUPPLY VOLTAGE
vs. LOAD RESISTANCE
20
18
16
14
12
10
8
100
90
80
70
60
50
40
30
20
10
0
20
18
V
A
= 15V
DD
R = 16Ω
L
= 16dB
V
THD+N = 10%
16
14
12
10
8
R = 8Ω
L
R = 8Ω
L
R = 16Ω
L
6
6
THD+N = 1%
4
V
A
= 15V
= 16dB
4
DD
A
= 16dB
V
V
2
2
THD+N = 10%
f = 1kHz
0
0
0
2
4
6
8
10 12 14 16 18 20
1
10
100
10
13
16
19
22
25
OUTPUT POWER (W)
SUPPLY VOLTAGE (V)
LOAD RESISTANCE (Ω)
COMMON-MODE REJECTION RATIO
vs. FREQUENCY
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
OUTPUT POWER
vs. LOAD RESISTANCE
0
-10
-20
-30
-40
-50
-60
-70
-80
0
24
22
20
18
16
14
12
10
8
V
A
= 20V
= 16dB
V
= 15V
A
= 16dB
DD
DD
V
R = 8Ω
R = 8Ω
200mV INPUT
V
THD+N = 10%
L
L
-20
-40
A
= 16dB
V
P-P
= 15V
V
DD
-60
-80
THD+N = 1%
6
-100
4
2
-120
0
1
10
100
10
100
1k
10k
100k
10
100
1k
FREQUENCY (Hz)
10k
100k
LOAD RESISTANCE (Ω)
FREQUENCY (Hz)
OUTPUT FREQUENCY SPECTRUM
OUTPUT FREQUENCY SPECTRUM
CROSSTALK vs. FREQUENCY
0
-20
20
0
20
0
A
= 16dB
FFM MODE
SSM MODE
V
1% THD+N
= 15V
A
V
= 16dB
A = 16dB
V
V
UNWEIGHTED
= 1kHz
UNWEIGHTED
f = 1kHz
IN
DD
8Ω LOAD
-20
f
-20
IN
P
= 5W
P
= 5W
OUT
OUT
-40
-40
-40
R = 8Ω
R = 8Ω
L
L
LEFT TO RIGHT
-60
-60
-60
-80
-80
-80
-100
-120
-140
-100
-120
-140
RIGHT TO LEFT
-100
-120
0
2
4
6
8
10 12 14 16 18 20
10
100
1k
10k
100k
0
2
4
6
8
10 12 14 16 18 20
FREQUENCY (Hz)
FREQUENCY (kHz)
FREQUENCY (kHz)
Maxim Integrated
│ 5
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Typical Operating Characteristics (continued)
(33μH with 4Ω, 68μH with 8Ω, part in SSM mode, 136μH with 16Ω, measurement BW = 22Hz to 22kHz, unless otherwise noted.)
WIDEBAND OUTPUT SPECTRUM
(FFM MODE)
WIDEBAND OUTPUT SPECTRUM
(SSM MODE)
OUTPUT FREQUENCY SPECTRUM
20
0
0
-20
0
-20
SSM MODE
RBW = 10kHz
RBW = 10kHz
A
V
= 16dB
V
DD
= 15V
V
DD
= 15V
A-WEIGHTED
f = 1kHz
IN
-20
P
= 5W
OUT
-40
-40
-40
R = 8Ω
L
-60
-60
-60
-80
-80
-80
-100
-120
-140
-100
-120
-100
-120
100k
1M
10M
100M
100k
1M
10M
100M
0
2
4
6
8
10 12 14 16 18 20
FREQUENCY (kHz)
FREQUENCY (Hz)
FREQUENCY (Hz)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE
TURN-ON/TURN-OFF RESPONSE
MAX9703/04 toc22
35
0.35
C
SS
= 180pF
30
25
0.30
0.25
0.20
0.15
SHDN
5V/div
1V/div
20
15
10
0.10
0.05
OUTPUT
5
0
f = 1kHz
R = 8Ω
L
0
10
13
16
19
22
25
10
12
14
16
18
20
20ms/div
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
Maxim Integrated
│ 6
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Pin Description
PIN
NAME
FUNCTION
MAX9703
MAX9704
1, 2, 23, 24
1, 2, 23, 24
PGND
Power Ground
3, 4, 21, 22
3, 4, 21, 22
V
Power-Supply Input
DD
5
6
7
5
6
7
C1N
C1P
Charge-Pump Flying Capacitor Negative Terminal
Charge-Pump Flying Capacitor Positive Terminal
CHOLD Charge-Pump Hold Capacitor. Connect a 1µF capacitor from CHOLD to V
.
DD
8, 17, 20, 25,
26, 31, 32
8
N.C.
No Connection. Not internally connected.
9
14
13
—
—
12
REG
AGND
IN-
6V Internal Regulator Output. Bypass with a 0.01µF capacitor to AGND.
10
11
12
13
Analog Ground
Negative Input
Positive Input
IN+
SS
Soft-Start. Connect a 0.47µF capacitor from SS to PGND to enable soft-start feature.
Active-Low Shutdown. Connect SHDN to PGND to disable the device. Connect to a
logic-high for normal operation.
14
11
SHDN
15
16
17
18
G1
G2
Gain-Select Input 1
Gain-Select Input 2
18
19
FS1
Frequency-Select Input 1
19
20
FS2
Frequency-Select Input 2
27, 28
29, 30
—
—
OUT-
OUT+
INL-
Negative Audio Output
—
Positive Audio Output
9
Left-Channel Negative Input
Left-Channel Positive Input
Right-Channel Negative Input
Right-Channel Positive Input
Right-Channel Negative Audio Output
Right-Channel Positive Audio Output
Left-Channel Negative Audio Output
Left-Channel Positive Audio Output
Exposed Paddle. Connect to PGND.
—
10
INL+
INR-
—
15
—
16
INR+
OUTR-
OUTR+
OUTL-
OUTL+
EP
—
25, 26
27, 28
29, 30
31, 32
—
—
—
—
—
Maxim Integrated
│ 7
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Table 1. Operating Modes
Detailed Description
The MAX9703/MAX9704 filterless, Class D audio power
amplifiers feature several improvements to switchmode
amplifier technology. The MAX9703 is a mono amplifier,
the MAX9704 is a stereo amplifier. These devices offer
Class AB performance with Class D efficiency, while occu-
pying minimal board space. A unique filterless modulation
scheme and spread-spectrum switching mode create a
compact, flexible, lownoise, efficient audio power ampli-
fier. The differential input architecture reduces common-
mode noise pickup, and can be used without input-cou-
pling capacitors. The devices can also be configured as a
single-ended input amplifier.
SWITCHING MODE
FS1
FS2
(kHz)
L
L
L
H
L
670
940
H
H
470
H
670 ±7%
the speaker and cables. This mode is enabled by setting
FS1 = FS2 = H. In SSM mode, the switching frequency
varies randomly by ±7% around the center frequency
(670kHz). The modulation scheme remains the same, but
the period of the triangle waveform changes from cycle to
cycle. Instead of a large amount of spectral energy pres-
ent at multiples of the switching frequency, the energy
is now spread over a bandwidth that increases with fre-
quency. Above a few megahertz, the wideband spectrum
looks like white noise for EMI purposes (see Figure 1).
Comparators monitor the device inputs and compare the
complementary input voltages to the triangle waveform.
The comparators trip when the input magnitude of the
triangle exceeds their corresponding input voltage.
Operating Modes
Fixed-Frequency Modulation (FFM) Mode
The MAX9703/MAX9704 feature three FFM modes with
different switching frequencies (Table 1). In FFM mode,
the frequency spectrum of the Class D output consists of
the fundamental switching frequency and its associated
harmonics (see the Wideband Output Spectrum (FFM
Mode) graph in the Typical Operating Characteristics).
The MAX9703/ MAX9704 allow the switching frequency
to be changed by ±35%, should the frequency of one or
more of the harmonics fall in a sensitive band. This can be
done at any time and does not affect audio reproduction.
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 currentsteering
switches and consume negligible additional power. Any
power loss associated with the Class D output stage is
2
mostly due to the I R 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
powers. Under normal operating levels (typical music
reproduction levels), efficiency falls below 30%, whereas
the MAX9704 still exhibits >78% efficiency under the
same conditions (Figure 2).
Spread-Spectrum Modulation (SSM) Mode
The MAX9703/MAX9704 feature a unique spread-spec-
trum mode that flattens the wideband spectral compo-
nents, improving EMI emissions that may be radiated by
Maxim Integrated
│ 8
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
V
DD
C
C
IN
L1*
1000pF
L2*
IN
1000pF
L3*
MAX9704
C
C
IN
1000pF
L4*
IN
1000pF
*L1–L4 = 0.05Ω DCR, 70Ω AT 100MHz, 3A FAIR RITE FERRITE BEAD (2512067007Y3).
40
35
30
25
20
15
CE LIMIT
MAX9704 OUTPUT
SPECTRUM
10
5
30
100
200
300
400
500
600
700
800
900
1000
FREQUENCY (MHz)
Figure 1. MAX9704 EMI Spectrum, 9in PC Board trace, 3in Twisted-Pair Speaker Cable
Maxim Integrated
│ 9
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
EFFICIENCY vs. OUTPUT POWER
SS
100
90
80
70
60
50
40
30
20
10
0
MAX9703/
MAX9704
GPIO
MUTE SIGNAL
MAX9704
0.18µF
CLASS AB
Figure 3. MAX9703/MAX9704 Mute Circuit
Applications Information
V
DD
= 15V
f = 1kHz
R = 8Ω
Filterless Operation
L
Traditional class D amplifiers require an output filter to
recover the audio signal from the amplifier’s PWM out-
put. The filters add cost, increase the solution size of the
amplifier, and can decrease efficiency. The traditional
PWM scheme uses large differential output swings (2
2
4
6
8
20
0
10 12 14 16 18
OUTPUT POWER (W)
Figure 2. MAX9704 Efficiency vs. Class AB Efficiency
V
peak-to-peak) and causes large ripple currents. Any
DD
Shutdown
parasitic resistance in the filter components results in a
loss of power, lowering the efficiency.
The MAX9703/MAX9704 have a shutdown mode that
reduces power consumption and extends battery life.
Driving SHDN low places the device in low-power
(0.2μA) shutdown mode. Connect SHDN to a logic high
for normal operation.
The MAX9703/MAX9704 do not require an output fil-
ter. The devices rely on the inherent inductance of the
speaker coil and the natural filtering of both the speaker
and the human ear to recover the audio component of the
square-wave output. Eliminating the output filter results in
a smaller, less-costly, more-efficient solution.
Click-and-Pop Suppression
The MAX9703/MAX9704 feature comprehensive clicka-
nd-pop suppression that eliminates audible transients on
startup and shutdown. While in shutdown, the Hbridge is
pulled to PGND through 330kΩ. 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 Hbridge is subse-
quently enabled. Following startup, a soft-start function
gradually unmutes the input amplifiers. The value of the
soft-start capacitor has an impact on the click/pop levels.
Because the frequency of the MAX9703/MAX9704 output
is well beyond the bandwidth of most speakers, voice
coil movement due to the square-wave frequency is very
small. Although this movement is small, a speaker not
designed to handle the additional power can be dam-
aged. For optimum results, use a speaker with a series
inductance > 30μH. Typical 8Ω speakers exhibit series
inductances in the range of 30μH to 100μH. Optimum
efficiency is achieved with speaker inductances > 60μH.
For optimum performance, C should be at least 0.18μF
with a voltage rating of at least 7V.
SS
Internal Regulator Output (V
)
REG
The MAX9703/MAX9704 feature an internal, 6V regula-
tor output (V ). The MAX9703/MAX9704 REG output
Mute Function
REG
The MAX9703/MA9704 features a clickless/popless mute
mode. When the device is muted, the outputs stop
switching, muting the speaker. Mute only affects the out-
put stage and does not shut down the device. To mute
the MAX9703/MAX9704, drive SS to PGND by using a
MOSFET pulldown (Figure 3). Driving SS to PGND during
the power-up/down or shutdown/turn-on cycle optimizes
click-and-pop suppression.
pin simplifies system design and reduces system cost by
providing a logic voltage high for the MAX9703/ MAX9704
logic pins (G_, FS_). V
is not available as a logic
REG
voltage high in shutdown mode. Do not apply V
as a
REG
6V potential to surrounding system components. Bypass
REG with a 6.3V, 0.01μF capacitor to AGND.
Maxim Integrated
│ 10
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Gain Selection
The MAX9703/MAX9704 feature an internally set, logic-
selectable gain. The G1 and G2 logic inputs set the gain
of the MAX9703/MAX9704 speaker amplifier (Table 2).
0.47µF
SINGLE-ENDED
AUDIO INPUT
IN+
MAX9703/
MAX9704
IN-
Table 2. Gain Selection
0.47µF
G1
0
G2
0
GAIN (dB)
29.6
0
1
19.1
Figure 4. Single-Ended Input
1
0
13
1
1
16
the signal to an optimum DC level. Assuming zero-source
impedance, the -3dB point of the highpass filter is given by:
Output Offset
1
f
=
-
Unlike a Class AB amplifier, the output offset voltage of
Class D amplifiers does not noticeably increase quiescent
current draw when a load is applied. This is due to the
power conversion of the Class D amplifier. For example,
an 8mV DC offset across an 8Ω load results in 1mA extra
current consumption in a class AB device. In the Class
D case, an 8mV offset into 8Ω equates to an additional
power drain of 8μW. Due to the high efficiency of the
Class D amplifier, this represents an additional quiescent
3dB
2πR C
IN IN
Choose C so f
interest. Setting f
is well below the lowest frequency of
too high affects the low-frequency
IN
-3dB
-3dB
response of the amplifier. Use capacitors with dielectrics
that have low-voltage coefficients, such as tantalum or
aluminum electrolytic. Capacitors with highvoltage coef-
ficients, such as ceramics, may result in increased distor-
tion at low frequencies.
current draw of: 8μW/(V /100 x η), which is in the order
DD
of a few microamps.
Charge-Pump Capacitor Selection
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 per-
formance over the extended temperature range, select
capacitors with an X7R dielectric.
Input Amplifier
Differential Input
The MAX9703/MAX9704 feature a differential input struc-
ture, making them compatible with many CODECs, and
offering improved noise immunity over a single-ended
input amplifier. In devices such as PCs, noisy digital sig-
nals can be picked up by the amplifier’s input traces. The
signals appear at the amplifiers’ inputs as commonmode
noise. A differential input amplifier amplifies the difference
of the two inputs, any signal common to both inputs is
canceled.
Flying Capacitor (C1)
The value of the flying capacitor (C1) affects the load
regulation and output resistance of the charge pump. A
C1 value that is too small degrades the device’s ability to
provide sufficient current drive. Increasing the value of C1
improves load regulation and reduces the chargepump
output resistance to an extent. Above 1μF, the onresis-
tance of the switches and the ESR of C1 and C2 dominate.
Single-Ended Input
The MAX9703/MAX9704 can be configured as singleen-
ded input amplifiers by capacitively coupling either input
to AGND and driving the other input (Figure 4).
Hold Capacitor (C2)
The output capacitor value and ESR directly affect the
ripple at CHOLD. Increasing C2 reduces output ripple.
Likewise, decreasing the ESR of C2 reduces both ripple
and output resistance. Lower capacitance values can be
used in systems with low maximum output power levels.
Component Selection
Input Filter
An input capacitor, C , in conjunction with the input
IN
impedance of the MAX9703/MAX9704, forms a highpass
filter that removes the DC bias from an incoming signal.
The AC-coupling capacitor allows the amplifier to bias
Output Filter
The MAX9703/MAX9704 do not require an output filter
and can pass FCC emissions standards with unshielded
speaker cables. However, output filtering can be used if a
Maxim Integrated
│ 11
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
design is failing radiated emissions due to board layout or
cable length, or the circuit is near EMIsensitive devices.
Use a ferrite bead filter when radiated frequencies above
10MHz are of concern. Use an LC filter when radiated
frequencies below 10MHz are of concern, or when long
leads connect the amplifier to the speaker. Refer to the
MAX9704 Evaluation Kit schematic for details of this filter.
Audio content, both music and voice, has a much lower
RMS value relative to its peak output power. Figure
5 shows a sine wave and an audio signal in the time
domain. Both are measured for RMS value by the oscil-
loscope. Although the audio signal has a slightly higher
peak value than the sine wave, its RMS value is almost
half that of the sine wave. Therefore, while an audio sig-
nal may reach similar peaks as a continuous sine wave,
the actual thermal impact on the Class D amplifier is
highly reduced. If the thermal performance 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 performance will be less than
the system’s actual capability.
Sharing Input Sources
In certain systems, a single audio source can be shared
by multiple devices (speaker and headphone ampli-
fiers). When sharing inputs, it is common to mute the
unused device, rather than completely shutting it down,
preventing the unused device inputs from distorting the
input signal. Mute the MAX9703/MAX9704 by driving SS
low through an open-drain output or MOSFET (see the
System Diagram). Driving SS low turns off the Class D
output stage, but does not affect the input bias levels of
the MAX9703/MAX9704. Be aware that during normal
operation, the voltage at SS can be up to 7V, depending
on the MAX9703/MAX9704 supply.
PC Board Thermal Considerations
The exposed pad is the primary route of keeping 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
large copper polygon. Add as much copper as possible
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 capabilities of
the system.
Supply Bypassing/Layout
Proper power-supply bypassing ensures low distortion
operation. For optimum performance, bypass V
to
DD
PGND with a 0.1μF capacitor as close to each V
pin
DD
as possible. A low-impedance, high-current power-supply
connection to V is assumed. Additional bulk capaci-
DD
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 sys-
tem’s constraints for signal routing.
tance should be added as required depending on the
application and power-supply characteristics. AGND and
PGND should be star connected to system ground. Refer
to the MAX9704 Evaluation Kit for layout guidance.
Class D Amplifier Thermal
Considerations
Class D amplifiers provide much better efficiency and ther-
mal performance than a comparable Class AB amplifier.
However, the system’s thermal performance must be consid-
ered with realistic expectations and include consideration of
many parameters. This section examines Class D amplifiers
using general examples to illustrate good design practices.
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 maximum output
power with a continuous sine wave.
20ms/div
Figure 5. RMS Comparison of Sine Wave vs. Audio Signal
Maxim Integrated
│ 12
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
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 of the package, they
do provide a small amount. The total improvement would
not exceed about 10%, but it could make the difference
between acceptable performance and thermal problems.
Decreasing the ambient temperature or reducing θ
will improve the die temperature of the MAX9704. θ
can be reduced by increasing the copper size/weight of
the ground plane connected to the exposed paddle of
JA
JA
the MAX9704 TQFN package. Additionally, θ
can be
JA
reduced by attaching a heatsink, adding a fan, or mount-
ing a vertical PC board.
Auxiliary Heatsinking
Load Impedance
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 costef-
fective location for a heatsink.
The on-resistance of the MOSFET output stage in Class
D amplifiers affects both the efficiency and the peak-
current capability. Reducing the peak current into the load
2
reduces the I R losses in the MOSFETs, thereby increas-
ing efficiency. To keep the peak currents lower, choose
the highest impedance speaker which can still deliver the
desired output power within the voltage swing limits of the
Class D amplifier and its supply voltage.
Although most loudspeakers are either 4Ω or 8Ω, there
are other impedances available which can provide a more
thermally efficient solution.
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:
Another consideration is the load impedance across
the audio frequency band. A loudspeaker is a complex
electromechanical system with a variety of resonances.
In other words, an 8Ω speaker is usually only 8Ω imped-
ance within a very narrow range, and 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
multi-driver audio system.
● T = +40°C
A
● P
= 2x8W = 16W
OUT
● R = 16Ω
L
● Efficiency (η) = 87%
● θ = 27°C/W
JA
First, the Class D amplifier’s power dissipation must be
calculated.
Optimize MAX9703/MAX9704 Efficiency with
Load Impedance and Supply Voltage
P
16W
0.87
OUT
η
P
=
− P
=
OUT
−16W = 2.4W
DISS
To optimize the efficiency of the MAX9703/MAX9704,
load the output stage with 12Ω to 16Ω speakers. The
MAX9703/MAX9704 exhibits highest efficiency perfor-
mance when driving higher load impedance (see the
Typical Operating Characteristics). If a 12Ω to 16Ω load is
not available, select a lower supply voltage when driving
6Ω to 10Ω loads.
Then the power dissipation is used to calculate the die
temperature, T , as follows:
C
T
= T + PDISS x θ
A JA
C
= 40°C + 2.4W x 27°C/W
= 104.8°C
Maxim Integrated
│ 13
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Functional Diagrams
10V TO 25V
100µF*
†
25V
0.1µF
†
0.1µF
†
25V
25V
1
2
3
4
21 22
23 24
PGND
PGND
V
V
DD
DD
0.47µF
0.47µF
IN+
OUT+ 30
OUT+
12
11
29
OUT- 28
MODULATOR
OSCILLATOR
H-BRIDGE
IN-
27
OUT-
18
19
FS1
FS2
V
REG
V
REG
MAX9703
14
SHDN
15 G1
GAIN
CONTROL
V
V
REG
16 G2
REG
6
5
C1P
C1N
C1
0.1µF
25V
13 SS
SHUTDOWN
CONTROL
CHARGE PUMP
CHOLD
0.18µF
10V
V
REG
REG
9
†
0.01µF
10V
10 AGND
7
C2
1µF
†
25V
V
DD
LOGIC INPUTS SHOWN FOR A = 16dB (SSM).
V
V
= LOGIC HIGH > 2.5V.
IN
†
CHOOSE CAPACITOR VOLTAGE RATING V
*SYSTEM-LEVEL REQUIREMENT.
.
DD
Maxim Integrated
│ 14
www.maximintegrated.com
MAX9703/MAX9704
Functional Diagrams (continued)
100µF*
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
10V TO 25V
†
25V
0.1µF
25V
0.1µF
25V
†
†
1
2
3
4
21 22
23 24
PGND
PGND
V
V
DD
DD
0.47µF
10 INL+
OUTL+ 32
OUTL+
31
OUTL- 30
29
MODULATOR
0.47µF
H-BRIDGE
9
INL-
OUTL-
19
20
FS1
FS2
V
REG
OSCILLATOR
MODULATOR
V
REG
0.47µF
0.47µF
INR+
INR-
OUTR+ 28
OUTR+
16
15
27
H-BRIDGE
OUTR- 26
OUTR- 25
11
SHDN
MAX9704
17 G1
18 G2
12 SS
V
REG
GAIN
CONTROL
V
REG
6
5
C1P
C1N
C1
SHUTDOWN
CONTROL
CHARGE PUMP
0.18µF
10V
0.1µF
25V
V
REG
REG
14
†
0.01µF
10V
13 AGND
CHOLD
7
C2
1µF
†
25V
V
DD
LOGIC INPUTS SHOWN FOR A = 16dB (SSM).
V
V
= LOGIC HIGH > 2.5V.
IN
†
CHOOSE CAPACITOR VOLTAGE RATING V
*SYSTEM-LEVEL REQUIREMENT.
.
DD
Maxim Integrated
│ 15
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
System Diagram
V
DD
100µF*
1µF
SHDN
V
DD
0.47µF
OUTL-
INL-
OUTL-
0.47µF
INL+
OUTL+
OUTL+
CODEC
MAX9704
0.47µF
0.47µF
OUTR+
INR+
OUTR+
OUTR-
INR-
SS
OUTR-
5V
100kΩ
0.18µF
SHDN
INL-
1µF
V
DD
MAX9722B
1µF
1µF
15kΩ
15kΩ
OUTL
INL+
OUTR
INR+
1µF
PV
SV
SS
INR-
SS
1µF
C1P
CIN
30kΩ
30kΩ
1µF
LOGIC INPUTS SHOWN FOR A = 16dB (SSM).
V
*BULK CAPACITANCE, IF NEEDED.
Maxim Integrated
│ 16
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Pin Configurations
TOP VIEW
23 22 21 20 19 18 17
23 22 21 20 19 18 17
24
24
N.C. 25
N.C. 26
OUT- 27
OUT- 28
OUT+ 29
OUT+ 30
N.C. 31
16 G2
OUTR- 25
OUTR- 26
OUTR+ 27
OUTR+ 28
OUTL- 29
OUTL- 30
OUTL+ 31
16 INR+
15 INR-
14 REG.
13 AGND
12 SS
15 G1
14 SHDN
13 SS
MAX9704
MAX9703
12 IN+
11 IN-
11 SHDN
10 INL+
10 AGND
N.C.
9
REG.
OUTL+
9
INL-
32
32
2
3
4
5
6
7
8
2
3
4
5
6
7
8
1
1
TQFN (5mm x 5mm)
TQFN (7mm x 7mm)
Chip Information
MAX9703 TRANSISTOR COUNT: 3093
MAX9704 TRANSISTOR COUNT: 4630
PROCESS: BiCMOS
Maxim Integrated
│ 17
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
PACKAGE TYPE
32 TQFN-EP (Mono)
32 TQFN-EP (Stereo)
PACKAGE CODE
T3255-4
OUTLINE NO.
21-0144
LAND PATTERN NO.
90-0012
T3277-2
21-0140
90-0125
Maxim Integrated
│ 18
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Package Information (continued)
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
Maxim Integrated
│ 19
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Package Information (continued)
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
Maxim Integrated
│ 20
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Package Information (continued)
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
Maxim Integrated
│ 21
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Package Information (continued)
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
Maxim Integrated
│ 22
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Package Information (continued)
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
Maxim Integrated
│ 23
www.maximintegrated.com
MAX9703/MAX9704
10W Stereo/15W Mono, Filterless,
Spread-Spectrum, Class D Amplifiers
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
Removed automotive reference in Applications section and corrected
package code
8
5/14
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
©
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
2014 Maxim Integrated Products, Inc.
│ 24
相关型号：
MAX9704ETJ+
Audio Amplifier, 16W, 2 Channel(s), 1 Func, BICMOS, PQCC32, 7 X 7 MM, 0.80 MM HEIGHT, LEAD FREE, MO-220, TQFN-32
MAXIM
MAX9704ETJ+T
Audio Amplifier, 20W, 2 Channel(s), 1 Func, BICMOS, 7 X 7 MM, 0.80 MM HEIGHT, TQFN-32
MAXIM
MAX9704ETJ-T
Audio Amplifier, 20W, 2 Channel(s), 1 Func, BICMOS, 7 X 7 MM, 0.80 MM HEIGHT, MO-220, TQFN-32
MAXIM
MAX9705AETB+
Audio Amplifier, 2.3W, 1 Channel(s), 1 Func, BICMOS, 3 X 3 MM, 0.80 MM HEIGHT, LEAD FREE, MO-229WEED-3, TDFN-10
MAXIM
©2020 ICPDF网 联系我们和版权申明