MAX9705DEUB+ [MAXIM]
2.3W, Ultra-Low-EMI, Filterless, Class D Audio Amplifier; 2.3W ，超低EMI ，无需滤波的D类音频放大器
| 型号： | MAX9705DEUB+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 2.3W, Ultra-Low-EMI, Filterless, Class D Audio Amplifier |
| 文件： | 总20页 (文件大小：2358K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-3405; Rev 0; 7/05
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
General Description
Features
♦ Filterless Amplifier Passes FCC-Radiated
The MAX9705 3rd-generation, ultra-low EMI, mono, Class
D audio power amplifier provides Class AB performance
with Class D efficiency. The MAX9705 delivers 2.3W into
a 4Ω load and offers efficiencies above 85%. Active
emissions limiting (AEL) circuitry greatly reduces EMI by
actively controlling the output FET gate transitions under
all possible transient output-voltage conditions. AEL pre-
vents high-frequency emissions resulting from conven-
tional Class D free-wheeling behavior in the presence of
an inductive load. Zero dead time (ZDT) technology
maintains state-of-the-art efficiency and THD+N perfor-
mance by allowing the output FETs to switch simultane-
ously without cross-conduction. A patented spread-
spectrum modulation scheme eliminates the need for out-
put filtering found in traditional Class D devices. These
design concepts reduce an application’s component
count and extend battery life.
Emissions Standards with 24in of Cable
♦ Unique Spread-Spectrum Mode and Active
Emissions Limiting (AEL) Achieves Better than
20dB Margin Under FCC Limits
♦ Zero Dead Time (ZDT) H-Bridge Maintains State-
of-the-Art Efficiency and THD+N
♦ Simple Master-Slave Setup for Stereo Operation
♦ Up to 90% Efficiency
♦ 2.3W into 4Ω (1% THD+N)
♦ Low 0.02% THD+N (P
= 1W, V
= 5.0V)
OUT
DD
♦ High PSRR (75dB at 217Hz)
♦ Integrated Click-and-Pop Suppression
♦ Low Quiescent Current (5.4mA)
♦ Low-Power Shutdown Mode (0.3µA)
♦ Short-Circuit and Thermal-Overload Protection
The MAX9705 offers two modulation schemes: a fixed-
frequency (FFM) mode and a spread-spectrum (SSM)
mode that further reduces EMI-radiated emissions due to
the modulation frequency. The MAX9705 oscillator can
be synchronized to an external clock through the SYNC
input, allowing the switching frequency to be externally
defined. The SYNC input also allows multiple MAX9705s
to be cascaded and frequency locked, minimizing inter-
ference due to clock intermodulation. The device utilizes
a fully differential architecture, a full-bridged output, and
comprehensive click-and-pop suppression. The gain of
the MAX9705 is set internally (MAX9705A: 6dB,
MAX9705B: 12dB, MAX9705C: 15.6dB, MAX9705D:
20dB), further reducing external component count.
♦ Available in Thermally Efficient, Space-Saving
Packages
10-Pin TDFN (3mm x 3mm x 0.8mm)
10-Pin µMAX
12-Bump UCSP (1.5mm x 2mm x 0.6mm)
♦ Pin-for-Pin Compatible with the MAX9700 and
MAX9712
Ordering Information
PIN-
PACKAGE
TOP
MARK
PART
TEMP RANGE
MAX9705AETB+T
MAX9705AEUB+
MAX9705AEBC+T
MAX9705BETB+T
MAX9705BEUB+
MAX9705BEBC+T
-40oC to +85oC 10 TDFN-10
-40oC to +85oC 10 µMAX
-40oC to +85oC 12 UCSP-12
-40oC to +85oC 10 TDFN-10
-40oC to +85oC 10 µMAX
-40oC to +85oC 12 UCSP-12
ACY
—
The MAX9705 is available in 10-pin TDFN (3mm x 3mm x
ACH
ACX
—
®
0.8mm), 10-pin µMAX , and 12-bump UCSP™ (1.5mm x
2mm x 0.6mm) packages. The MAX9705 is specified over
the extended -40°C to +85°C temperature range.
ACG
Ordering Information continued at end of data sheet.
+Denotes lead-free package.
Applications
EMI Spectrum Diagram
Cellular Phones
PDAs
MP3 Players
Portable Audio
50.0
45.0
40.0
FCC EMI LIMIT
35.0
30.0
25.0
20.0
15.0
10.0
5.0
Selector Guide appears at end of data sheet.
MAXIM'S NEW ULTRA-LOW
OUTPUT SPECTRUM
30.0
60.0 80.0 100.0 120.0 140.0 160.0 180.0 200.0 220.0 240.0 260.0 280.0 300.0
FREQUENCY (MHz)
µMAX is a registered trademark and UCSP is a trademark of
Maxim Integrated Products, Inc.
________________________________________________________________ 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.
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
ABSOLUTE MAXIMUM RATINGS
V
to GND..............................................................................6V
Continuous Power Dissipation (T = +70°C)
A
DD
PV
to PGND .........................................................................6V
10-Pin TDFN (derate 24.4mW/°C above +70°C) .....1951.2mW
DD
o
GND to PGND .......................................................-0.3V to +0.3V
PV to V ..........................................................-0.3V to +0.3V
10-Pin µMAX (derate 5.6mW/ C above +70°C).........444.4mW
12-Bump UCSP (derate 6.1mW/°C above +70°C)........484mW
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
Bump Temperature (soldering)
DD
DD
All Other Pins to GND.................................-0.3V to (V
+ 0.3V)
DD
Continuous Current Into/Out of PV /PGND/OUT_........ 600mA
DD
Continuous Input Current (all other pins) ......................... 20mA
Duration of OUT_ Short Circuit to GND or PV ........Continuous
DD
Duration of Short Circuit Between OUT+ and OUT-.....Continuous
Reflow ..........................................................................+235°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
to T
= PV
= SHDN = 3.3V, GND = PGND = 0V, SYNC = GND (FFM), R = ∞, R connected between OUT+ and OUT-, T = T
DD L L A MIN
DD
, unless otherwise noted. Typical values are at T = +25°C.) (Notes 1, 2)
MAX
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
GENERAL
Supply Voltage Range
Quiescent Current
Shutdown Current
Turn-On Time
V
Inferred from PSRR test
2.5
5.5
7
V
DD
I
5.4
0.3
30
mA
µA
ms
kΩ
DD
I
10
SHDN
t
ON
Input Resistance
R
T
A
= +25°C
12
20
IN
MAX9705A
MAX9705B
MAX9705C
MAX9705D
0.88
0.73
0.61
0.48
1.9
1.0
1.12
0.93
0.81
0.64
2.1
0.83
0.71
0.56
2.0
Input Bias Voltage
Voltage Gain
V
Either input
V
BIAS
MAX9705A
MAX9705B
MAX9705C
MAX9705D
3.8
5.7
9.5
4.0
6.0
10
4.2
6.3
10.5
69
A
V/V
V
Output Offset Voltage
V
T
A
= +25°C
10
mV
dB
OS
Common-Mode Rejection Ratio
CMRR
f
= 1kHz, input referred
56
IN
V
= 2.5V to 5.5V, T = +25°C
50
75
DD
A
Power-Supply Rejection Ratio
(Note 3)
PSRR
dB
f
f
= 217Hz
= 20kHz
75
RIPPLE
RIPPLE
200mV
ripple
P-P
60
R = 8Ω
600
950
L
THD+N = 1%,
Output Power
P
mW
OUT
f
IN
= 1kHz
R = 4Ω
L
R = 8Ω,
L
0.02
P
= 450mW
OUT
Total Harmonic Distortion
Plus Noise
f
= 1kHz, either FFM or
IN
THD+N
%
SSM
R = 4Ω,
L
0.025
P
= 375mW
OUT
Into shutdown
-68
Peak voltage,
A-weighted (Notes 3, 4)
Click/Pop Level
K
dB
CP
Out of shutdown
-60.5
2
_______________________________________________________________________________________
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
ELECTRICAL CHARACTERISTICS (continued)
(V
to T
= PV
= SHDN = 3.3V, GND = PGND = 0V, SYNC = GND (FFM), R = ∞, R connected between OUT+ and OUT-, T = T
DD L L A MIN
DD
, unless otherwise noted. Typical values are at T = +25°C.) (Notes 1, 2)
MAX
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
176
15
MAX
UNITS
Output Slew Rate
Rise/Fall Time
SR
V/µs
ns
t
, t
10% to 90%
RISE FALL
FFM
SSM
FFM
SSM
91
BW = 22Hz
to 22kHz
89
Signal-to-Noise Ratio
Oscillator Frequency
SNR
V
= 2V
dB
OUT
RMS
93
A-weighted
91
SYNC = GND
SYNC = float
980
1100
1450
1220
1650
1250
f
kHz
OSC
1220
120
SYNC = V
(SSM mode)
DD
SYNC Frequency Lock Range
Efficiency
800
2
2000
kHz
%
η
P
= 800mW, f = 1kHz, R = 8Ω
89
OUT
IN
L
DIGITAL INPUTS (SHDN, SYNC)
V
V
IH
IL
Input Thresholds
V
0.8
10
10
SHDN Input Leakage Current
0.1
µA
µA
SYNC Input Current
(Note 5)
-1.25
ELECTRICAL CHARACTERISTICS
(V
= PV
= SHDN = 5V, GND = PGND = 0V, SYNC = GND (FFM), R = ∞, R connected between OUT+ and OUT-, T = T
to
DD
DD
L
L
A
MIN
T
, unless otherwise noted. Typical values are at T = +25°C.) (Notes 1, 2)
MAX
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
7
MAX
UNITS
mA
Quiescent Current
Shutdown Current
I
DD
I
0.55
75
µA
SHDN
f = 217Hz
Power-Supply Rejection Ratio
PSRR
200mV
ripple
dB
mW
%
P-P
f = 20kHz
R = 16Ω
60
750
1400
2300
0.02
0.05
94
L
THD+N = 1%,
f = 1kHz
Output Power
P
R = 8Ω
L
OUT
R = 4Ω
L
R = 8Ω, P
R = 4Ω, P
L
= 1.0W
Total Harmonic Distortion
Plus Noise
f = 1kHz, either
FFM or SSM
L
OUT
THD+N
SNR
= 1.75W
OUT
FFM
SSM
FFM
SSM
BW = 22Hz to
22kHz
91
V
=
OUT
Signal-to-Noise Ratio
dB
3V
RMS
97
A-weighted
93
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 = 4Ω, L = 33µH.
L
For R = 8Ω, L = 68µH. For R = 16Ω, L = 136µH.
L
L
Note 3: Inputs AC-coupled to GND.
Note 4: Testing performed with 8Ω resistive load in series with 68µH inductive load connected across BTL output. Mode transitions
are controlled by SHDN pin. K level is calculated as 20 x log[(peak voltage under normal operation at rated power
CP
level)/(peak voltage during mode transition, no input signal)]. Units are expressed in dB.
Note 5: SYNC has a 1MΩ resistor to V
= 1.25V.
REF
_______________________________________________________________________________________
3
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
Typical Operating Characteristics
(V
= 3.3V, SYNC = V
(SSM), differential input, T = +25°C, unless otherwise noted.)
DD
DD A
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
100
100
10
1
100
10
1
f
= 1kHz
IN
10
1
0.1
0.1
0.1
f = 1kHz
IN
0.01
0.01
0.01
V
= 3.3V
V
= 5.0V
V
= 2.5V
DD
L
DD
L
DD
L
f
= 1kHz
IN
R = 8Ω
R = 8Ω
R = 4Ω
0.001
0.001
0.001
0
0.2
0.4
0.6
0.8
1.0
1.2
0
0.5
1.0
OUTPUT POWER (W)
1.5
2.0
0
0.2
0.4
OUTPUT POWER (W)
0.6
0.8
OUTPUT POWER (W)
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
100
10
1
100
10
1
100
V
= 3.3V
DD
R = 8Ω
L
f
= 1kHz
IN
10
1
SSM
FFM
0.1
0.1
0.1
0.01
0.01
0.01
f
= 1kHz
IN
f
= 1kHz
IN
V
= 3.3V
V
= 5.0V
DD
DD
R = 4Ω
L
R = 4Ω
L
0.001
0.001
0.001
0
0.5
1.0
1.5
0
0.5
1.0
1.5
2.0
2.5
3.0
0
0.2
0.4
0.6
0.8
1.0
1.2
OUTPUT POWER (W)
OUTPUT POWER (W)
OUTPUT POWER (W)
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
100
10
100
10
100
10
V
= 2.5V
V
= 3.3V
V
= 5.0V
DD
R = 8Ω
DD
DD
R = 4Ω
R = 8Ω
L
L
L
P
= 50mW
OUT
P
= 100mW
P
= 250mW
OUT
OUT
1
1
1
P
= 300mW
OUT
P
= 450mW
P
= 1W
0.1
0.01
0.1
0.01
0.1
0.01
OUT
OUT
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
FREQUENCY (Hz)
10k
100k
4
_______________________________________________________________________________________
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
Typical Operating Characteristics (continued)
(V
= 3.3V, SYNC = V
(SSM), differential input, T = +25°C, unless otherwise noted.)
DD
DD A
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
100
100
10
100
10
V
= 3.3V
V
= 5.0V
V
= 3.3V
DD
DD
DD
R = 4Ω
R = 4Ω
R = 8Ω
L
L
L
P
= 450mW
OUT
10
1
P
= 250mW
OUT
P
= 100mW
OUT
1
1
FFM
SSM
P
= 800mW
OUT
P
= 1.75W
OUT
0.1
0.01
0.1
0.01
0.1
0.01
10
100
1k
FREQUENCY (Hz)
10k
100k
10
100
1k
10k
100k
10
100
1k
10k
100k
FREQUENCY (Hz)
FREQUENCY (Hz)
EFFICIENCY
vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION PLUS
NOISE vs. COMMON-MODE VOLTAGE
EFFICIENCY
vs. OUTPUT POWER
100
100
100
V
= 3.3V to 5V
DD
R = 8Ω
90
80
70
60
50
40
30
20
10
0
L
R = 8Ω
L
90
80
70
60
50
40
30
20
10
0
f
IN
= 1kHz
P
= 500mW
OUT
10
1
GAIN = 6dB
R = 8Ω
L
R = 4Ω
R = 4Ω
L
L
0.1
0.01
V
= 3.3V
= 1kHz
DD
V
= 5.0V
= 1kHz
DD
f
IN
f
IN
0.001
0
0.2
0.4
0.6
0.8
1.0
0
0.5
1.0
1.5
2.0
2.5
0
0.5
1.0
1.5
2.0
2.5
3.0
OUTPUT POWER (W)
COMMON-MODE VOLTAGE (V)
OUTPUT POWER (W)
EFFICIENCY
vs. SUPPLY VOLTAGE
EFFICIENCY
vs. SYNC FREQUENCY
EFFICIENCY
vs. SYNC FREQUENCY
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
R = 8Ω
L
R = 8Ω
R = 8Ω
L
L
R = 4Ω
L
R = 4Ω
L
R = 4Ω
L
V
f
= 3.3V
= 1kHz
DD
IN
V
= 5.0V
DD
f
= 1kHz
IN
f = 1kHz
IN
THD+N = 1%
THD+N = 1%
THD+N = 1%
2.5
3.0
3.5
4.0
4.5
5.0 5.5
800 1000 1200 1400 1600 1800 2000
SYNC FREQUENCY (kHz)
800 1000 1200 1400 1600 1800 2000
SYNC FREQUENCY (kHz)
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
5
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
Typical Operating Characteristics (continued)
(V
= 3.3V, SYNC = V
(SSM), differential input, T = +25°C, unless otherwise noted.)
DD
DD A
OUTPUT POWER
vs. SUPPLY VOLTAGE
OUTPUT POWER
vs. SUPPLY VOLTAGE
OUTPUT POWER
vs. LOAD RESISTANCE
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
f
Z
= 1kHz
IN
= 33µH IN
LOAD
SERIES WITH R
THD+N = 1%
L
5.0V
THD+N = 10%
THD+N = 10%
3.3V
THD+N = 1%
THD+N = 1%
f
= 1kHz
IN
f
= 1kHz
IN
R = 8Ω
L
R = 4Ω
L
2.5
3.0
3.5
4.0
4.5
5.0
5.5
2.5
3.0
3.5
4.0
4.5
5.0
5.5
1
10
100
1000
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
LOAD RESISTANCE (Ω)
FIXED-FREQUENCY-MODE OUTPUT
SPECTRUM vs. FREQUENCY
POWER-SUPPLY REJECTION
RATIO vs. FREQUENCY
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
20
0
R = 8Ω
L
V
V
= 3.3V
DD
IN
L
V
= 5.0V
DD
= 200mV
P-P
f
IN
= 1kHz
R = 8Ω
BW = 22Hz to 22kHz
-20
-40
-60
-80
-100
-120
-140
10
100
1k
FREQUENCY (Hz)
10k
100k
0
5
10
FREQUENCY (kHz)
15
20
SPREAD-SPECTRUM-MODE OUTPUT
SPECTRUM vs. FREQUENCY
SPREAD-SPECTRUM-MODE OUTPUT
SPECTRUM vs. FREQUENCY
20
0
20
0
R = 8Ω
DD
L
R = 8Ω
DD
L
V
= 5.0V
V
= 5.0V
f
IN
= 1kHz
f = 1kHz
IN
BW = 22Hz to 22kHz
-20
-40
-60
-80
-100
-120
-140
A-WEIGHTED
-20
-40
-60
-80
-100
-120
-140
0
5
10
FREQUENCY (kHz)
15
20
0
5
10
15
20
FREQUENCY (kHz)
6
_______________________________________________________________________________________
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
Typical Operating Characteristics (continued)
(V
= 3.3V, SYNC = V
(SSM), differential input, T = +25°C, unless otherwise noted.)
DD
DD
A
WIDEBAND OUTPUT SPECTRUM
FIXED-FREQUENCY MODE
WIDEBAND OUTPUT SPECTRUM
SPREAD-SPECTRUM MODE
0
-20
0
-20
-40
-40
-60
-60
-80
-80
-100
-100
-120
-140
R = 8Ω
DD
INPUTS AC GROUNDED
L
V
R = 8Ω
L
= 5.0V
-120
-140
V
= 5.0V
DD
INPUTS AC GROUNDED
0
10
100
1000
0
10
100
1000
FREQUENCY (MHz)
FREQUENCY (MHz)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
SUPPLY CURRENT
vs. TEMPERATURE
10
7.00
6.75
6.50
6.25
6.00
5.75
5.50
5.25
5.00
V
= 3.3V
DD
NO LOAD
INPUTS AC GROUNDED
9
8
7
6
5
4
SYNC = V (SSM)
DD
SYNC = FLOAT (FFM)
SYNC = FLOAT (FFM)
SYNC = V (SSM)
DD
SYNC = GND (FFM)
NO LOAD
SYNC = GND (FFM))
INPUTS AC GROUNDED
2.5
3.5
4.5
5.5
-40
-15
10
35
60
85
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE
TURN-ON/TURN-OFF RESPONSE
MAX9705 toc31
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0
3V
SHDN
T
= -40°C
A
T
= +85°C
A
0V
T
= +25°C
A
MAX9705
OUTPUT
250mV/div
NO LOAD
INPUTS AC GROUNDED
SHDN = GND
2.5
3.0
3.5
4.0
4.5
5.0
5.5
10ms/div
f = 1kHz
R = 8Ω
SUPPLY VOLTAGE (V)
L
_______________________________________________________________________________________
7
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
Functional Diagram
2.5V TO 5.5V
1µF
1
10
6
(A1)
(B4)
(A3)
V
DD
PV
DD
SYNC
5
(B2)
SHDN
UVLO/POWER
MANAGEMENT
CLICK-AND-POP
SUPPRESSION
OSCILLATOR
PV
DD
LOW-EMI
DRIVER
2
(B1)
1µF
1µF
8
(A4)
IN+
IN-
OUT+
OUT-
PGND
CLASS D
MODULATOR
3
(C1)
PV
DD
9
(C4)
LOW-EMI
DRIVER
MAX9705
PGND
GND
PGND
7
4
(B3)
(C2)
( ) UCSP BUMP.
FIGURE SHOWS MAX9705 CONFIGURED FOR SPREAD-SPECTRUM OPERATION.
8
_______________________________________________________________________________________
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
Pin Description
PIN
BUMP
UCSP
A1
NAME
FUNCTION
TDFN/µMAX
1
2
3
4
5
V
Analog Power Supply
Noninverting Audio Input
Inverting Audio Input
Analog Ground
DD
B1
IN+
IN-
C1
C2
GND
SHDN
B2
Active-Low Shutdown Input. Connect to V
for normal operation.
DD
Frequency Select and External Clock Input.
SYNC = GND: Fixed-frequency mode with f = 1100kHz.
S
6
A3
SYNC
SYNC = Float: Fixed-frequency mode with f = 1450kHz.
S
SYNC = V : Spread-spectrum mode with f = 1220kHz 120kHz.
DD
S
SYNC = Clocked: Fixed-frequency mode with f = external clock frequency.
S
7
8
B3
A4
C4
B4
PGND
OUT+
OUT-
Power Ground
Amplifier-Output Positive Phase
Amplifier-Output Negative Phase
H-Bridge Power Supply
9
10
PV
DD
Comparators monitor the MAX9705 inputs and com-
Detailed Description
pare the complementary input voltages to the sawtooth
waveform. The comparators trip when the input magni-
tude of the sawtooth exceeds their corresponding input
voltage. Both comparators reset at a fixed time after the
rising edge of the second comparator trip point, gener-
The MAX9705 ultra-low-EMI, filterless, Class D audio
power amplifier features several improvements to switch-
mode amplifier technology. The MAX9705 features output
driver active emissions limiting circuitry to reduce EMI.
Zero dead time technology maintains state-of-the-art effi-
ciency and THD+N performance by allowing the output
FETs to switch simultaneously without cross-conduction.
A unique filterless modulation scheme, synchronizable
switching frequency, and spread-spectrum mode create
a compact, flexible, low-noise, efficient audio power
amplifier while occupying minimal board space. The dif-
ferential input architecture reduces common-mode noise
pickup with or without the use of input-coupling capaci-
tors. The MAX9705 can also be configured as a single-
ended input amplifier without performance degradation.
ating a minimum-width pulse t
at the output of
ON(MIN)
the second comparator (Figure 1). As the input voltage
increases or decreases, the duration of the pulse at one
output increases (the first comparator to trip), while the
other output pulse duration remains at t
. This
OUT+
ON(MIN)
causes the net voltage across the speaker (V
-
V
) to change.
OUT-
Operating Modes
Fixed-Frequency Modulation (FFM) Mode
The MAX9705 features two FFM modes. The FFM
modes are selected by setting SYNC = GND for a
1.1MHz switching frequency, and SYNC = FLOAT for a
1.45MHz switching frequency. In FFM mode, the fre-
quency spectrum of the Class D output consists of the
fundamental switching frequency and its associated
harmonics (see the Wideband FFT graph in the Typical
Operating Characteristics). The MAX9705 allows the
switching frequency to be changed by +32%, 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.
Thermal-overload and short-circuit protection prevent the
MAX9705 from being damaged during a fault condition.
The amplifier is disabled if the die temperature reaches
+150°C. The die must cool by 10°C before normal opera-
tion can continue. The output of the MAX9705 shuts down
if the output current reaches approximately 2A. Each out-
put FET has its own short-circuit protection. This protec-
tion scheme allows the amplifier to survive shorts to either
supply rail. After a thermal overload or short circuit, the
device remains disabled for a minimum of 50µs before
attempting to return to normal operation. The amplifier will
shut down immediately and wait another 50µs before turn-
ing on if the fault condition is still present. This operation
will cause the output to pulse during a persistent fault.
Spread-Spectrum Modulation (SSM) Mode
The MAX9705 features a unique, patented spread-spec-
trum mode that flattens the wideband spectral components,
_______________________________________________________________________________________
9
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
t
SW
V
IN-
V
IN+
OUT-
OUT+
t
ON(MIN)
V
OUT+
- V
OUT-
Figure 1. MAX9705 Outputs with an Input Signal Applied
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 (see the EMI Spectrum Diagram).
Table 1. Operating Modes
SYNC INPUT
GND
MODE
FFM with f = 1100kHz
S
FLOAT
FFM with f = 1450kHz
S
External Clock Mode
The SYNC input allows the MAX9705 to be synchronized
to a system clock moving the spectral components of the
switching harmonics to insensitive frequency bands.
Applying an external TTL clock of 800kHz to 2MHz to
SYNC synchronizes the switching frequency of the
MAX9705. The period of the SYNC clock can be ran-
domized, enabling the MAX9705 to be synchronized to
another MAX9705 operating in SSM mode.
V
SSM with f = 1220kHz 120kHz
S
DD
Clocked
FFM with f = external clock frequency
S
improving EMI emissions by 5dB. Proprietary techniques
ensure that the cycle-to-cycle variation of the switching
period does not degrade audio reproduction or efficiency
(see the Typical Operating Characteristics). Select SSM
mode by setting SYNC = V . In SSM mode, the switch-
DD
ing frequency varies randomly by 120kHz around the
center frequency (1.22MHz). The modulation scheme
remains the same, but the period of the sawtooth wave-
form changes from cycle to cycle (Figure 2). Instead of a
large amount of spectral energy present at multiples of
Filterless Modulation/Common-Mode Idle
The MAX9705 uses Maxim’s unique, patented modula-
tion scheme that eliminates the LC filter required by
traditional Class D amplifiers, improving efficiency,
reducing component count, and conserving board
10 ______________________________________________________________________________________
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
t
t
t
t
SW
SW
SW
SW
V
IN-
V
IN+
OUT-
OUT+
t
ON(MIN)
V
- V
OUT-
OUT+
Figure 2. MAX9705 Output with an Input Signal Applied (SSM Mode)
space and system cost. Conventional Class D amplifiers
output a 50% duty cycle square wave when no signal is
present. With no filter, the square wave appears across
the load as a DC voltage, resulting in a finite load cur-
rent, increasing power consumption. When no signal is
present at the input of the MAX9705, the outputs switch
as shown in Figure 3. Because the MAX9705 drives the
speaker differentially, the two outputs cancel each other,
resulting in no net idle-mode voltage across the speak-
er, minimizing power consumption.
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 powers. Under normal operating levels (typical
music reproduction levels), efficiency falls below 30%,
whereas the MAX9705 still exhibits >70% efficiencies
under the same conditions (Figure 4).
Shutdown
The MAX9705 has a shutdown mode that reduces power
consumption and extends battery life. Driving SHDN low
places the MAX9705 in a low-power (0.3µA) shutdown
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
mode. Connect SHDN to V
for normal operation.
DD
______________________________________________________________________________________ 11
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
EFFICIENCY vs. OUTPUT POWER
V
= 0V
100
90
80
70
60
50
40
30
20
10
0
IN
MAX9705
OUT-
CLASS AB
OUT+
V
= 3.3V
DD
f
= 1kHz
IN
R = 8Ω
L
0
0.2
0.4
0.6
0.8
1.0
OUTPUT POWER (W)
V
- V = 0V
OUT+ OUT-
Figure 3. MAX9705 Outputs with No Input Signal
Figure 4. MAX9705 Efficiency vs. Class AB Efficiency
designed to handle the additional power can be dam-
aged. For optimum results, use a speaker with a series
inductance >10µH. Typical 8Ω speakers exhibit series
inductances in the 20µH to 100µH range.
Click-and-Pop Suppression
The MAX9705 features comprehensive click-and-pop
suppression that eliminates audible transients on start-
up and shutdown. While in shutdown, the H-bridge is in
a high-impedance state. During startup or power-up,
the input amplifiers are muted and an internal loop sets
the modulator bias voltages to the correct levels, pre-
venting clicks and pops when the H-bridge is subse-
quently enabled. For 30ms following startup, a soft-start
function gradually unmutes the input amplifiers.
Power-Conversion Efficiency
Unlike a class AB amplifier, the output offset voltage of
a Class D amplifier does not noticeably increase quies-
cent-current draw when a load is applied. This is due to
the power conversion of the Class D amplifier. For exam-
ple, 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 addi-
tional power drain of 8µW. Due to the high efficiency of
the Class D amplifier, this represents an additional quies-
Applications Information
Filterless Operation
Traditional Class D amplifiers require an output filter to
recover the audio signal from the amplifier’s output. The
filters add cost, increase the solution size of the amplifi-
er, and can decrease efficiency and THD+N perfor-
mance. The traditional PWM scheme uses large
cent-current draw of 8µW/(V /100η), which is on the
DD
order of a few microamps.
Input Amplifier
differential output swings (2 x V
peak-to-peak) and
Differential Input
The MAX9705 features a differential input structure,
making it compatible with many CODECs, and offering
improved noise immunity over a single-ended input
amplifier. In devices such as cellular phones, high-fre-
quency signals from the RF transmitter can be picked
up by the amplifier’s input traces. The signals appear at
the amplifier’s inputs as common-mode noise. A differ-
ential input amplifier amplifies the difference of the two
inputs; any signal common to both inputs is canceled.
DD
causes large ripple currents. Any parasitic resistance in
the filter components results in a loss of power, lower-
ing the efficiency.
The MAX9705 does not require an output filter. The
device relies 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.
Single-Ended Input
The MAX9705 can be configured as a single-ended
input amplifier by capacitively coupling either input to
GND and driving the other input (Figure 5).
Because the frequency of the MAX9705 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
12 ______________________________________________________________________________________
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
Note that the single-ended voltage range of the
1µF
MAX9705A is 3V . This limits the achievable output
P-P
SINGLE-ENDED
AUDIO INPUT
power for this device. Use higher gain versions
(MAX9705B, MAX9705C, MAX9705D) if higher output
power is desired in a single-ended application.
IN+
IN-
MAX9705
DC-Coupled Input
The input amplifier can accept DC-coupled inputs that
are biased within the amplifier’s common-mode range
(see the Typical Operating Characteristics). DC cou-
pling eliminates the input-coupling capacitors, reduc-
ing component count to potentially one external
component (see the System Diagram). However, the
low-frequency rejection of the capacitors is lost, allow-
ing low-frequency signals to feed through to the load.
1µF
Figure 5. Single-Ended Input
Output Filter
The MAX9705 does not require an output filter. The
device passes FCC emissions standards with 24in of
unshielded twisted-pair speaker cables. However, an
output filter can be used if a design is failing radiated
emissions due to board layout or excessive cable
length, or the circuit is near EMI-sensitive devices.
Component Selection
Input Filter
An input capacitor, C , in conjunction with the input
IN
resistance of the MAX9705 forms a highpass filter that
removes the DC bias from an incoming signal. The AC-
coupling capacitor allows the amplifier to bias the sig-
nal to an optimum DC level. Assuming zero source
impedance, the -3dB point of the highpass filter is
given by:
Supply Bypassing/Layout
Proper power-supply bypassing ensures low-distortion
operation. For optimum performance, bypass V
to
DD
GND and PV
to PGND with separate 1µF capacitors
DD
as close to each pin as possible. A low-impedance,
high-current power-supply connection to PV is
DD
1
f−
=
assumed. Additional bulk capacitance should be added
as required depending on the application and power-
supply characteristics. GND and PGND should be star
connected to system ground. Refer to the MAX9705
evaluation kit for layout guidance.
3dB
2π R
C
IN
IN
Choose C so f
is well below the lowest frequency
-3dB
IN
-3dB
of interest. Setting f
too high affects the low-
frequency response of the amplifier. Use capacitors
whose dielectrics 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.
Stereo Configuration
Two MAX9705s can be configured as a stereo amplifier
(Figure 6). Device U1 is the master amplifier; its unfil-
tered output drives the SYNC input of the slave device
(U2), synchronizing the switching frequencies of the two
devices. Synchronizing two MAX9705s ensures that no
beat frequencies occur within the audio spectrum. This
configuration works when the master device is in either
FFM or SSM mode. There is excellent THD+N perfor-
mance and minimal crosstalk between devices due to
the SYNC connection (Figures 7 and 8). U2 locks onto
only the frequency present at SYNC, not the pulse
width. The internal feedback loop of device U2 ensures
that the audio component of U1’s output is rejected.
Other considerations when designing the input filter
include the constraints of the overall system and the
actual frequency band of interest. Although high-fidelity
audio calls for a flat gain response between 20Hz and
20kHz, portable voice-reproduction devices such as
cellular phones and two-way radios need only concen-
trate on the frequency range of the spoken human
voice (typically 300Hz to 3.5kHz). In addition, speakers
used in portable devices typically have a poor response
below 150Hz. Taking these two factors into considera-
tion, the input filter may not need to be designed for a
20Hz to 20kHz response, saving both board space and
cost due to the use of smaller capacitors.
______________________________________________________________________________________ 13
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
Designing with Volume Control
The MAX9705 can easily be driven by single-ended
sources (Figure 5), but extra care is needed if the
source impedance “seen” by each differential input is
unbalanced, such as the case in Figure 9a, where the
MAX9705 is used with an audio taper potentiometer
acting as a volume control. Functionally, this configura-
tion works well, but can suffer from click-pop transients
at power-up (or coming out of SHDN) depending on the
volume-control setting. As shown, the click-pop perfor-
mance is fine for either max or min volume, but worsens
at other settings.
V
DD
1µF
V
DD
PV
DD
MAX9705
IN+
IN-
OUT+
RIGHT-CHANNEL
DIFFERENTIAL
AUDIO INPUT
OUT-
One solution is the configuration shown in Figure 9b. The
potentiometer is connected between the differential
inputs, and these “see” identical RC paths when the
device powers up. The variable resistive element appears
between the two inputs, meaning the setting affects both
inputs the same way. The potentiometer is audio taper, as
in Figure 9a. This significantly improves transient perfor-
mance on power-up or release from SHDN. A similar
approach can be applied when the MAX9705 is driven
differentially and a volume control is required.
SYNC
1µF
V
DD
PV
DD
MAX9705
IN+
IN-
OUT+
LEFT-CHANNEL
DIFFERENTIAL
AUDIO INPUT
UCSP Applications Information
OUT-
For the latest application details on UCSP construction,
dimensions, tape carrier information, PC board tech-
niques, bump-pad layout, and recommended reflow tem-
perature profile, as well as the latest information on
reliability testing results, refer to Application Note:
UCSP—A Wafer-Level Chip-Scale Package available on
Maxim’s website at www.maxim-ic.com/ucsp.
SYNC
Figure 6. Master-Slave Stereo Configuration
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
CROSSTALK vs. FREQUENCY
0
100
V
= 3.3V
V
V
f
= 3.3V
DD
DD
IN
IN
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
SLAVE DEVICE
= 1kHz
SYNC = GND (FFM)
= 500mV
P-P
f
IN
= 1kHz
SYNC = GND (FFM)
R = 8Ω
10
R = 8Ω
L
L
1
0.1
MASTER TO SLAVE
0.01
0.001
SLAVE TO MASTER
10
100
1k
10k
100k
0
0.2
0.4
OUTPUT POWER (W)
0.6
0.8
FREQUENCY (Hz)
Figure 7. Master-Slave THD+N
Figure 8. Master-Slave Crosstalk
14 ______________________________________________________________________________________
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
1µF
22kΩ
CW
1µF
IN-
IN-
IN+
50kΩ
CW
50kΩ
MAX9705
MAX9705
1µF
IN+
22kΩ
1µF
Figure 9a. Single-Ended Drive of MAX9705 Plus Volume
Figure 9b. Improved Single-Ended Drive of MAX9705 Plus
Volume
Pin Configurations
Selector Guide
PART
PIN-PACKAGE
10 TDFN-10
10 µMAX
GAIN (dB)
TOP VIEW
+
MAX9705AETB+T
MAX9705AEUB+
MAX9705AEBC+T
MAX9705BETB+T
MAX9705BEUB+
MAX9705BEBC+T
MAX9705CETB+T
MAX9705CEUB+
MAX9705CEBC+T
MAX9705DETB+T
MAX9705DEUB+
MAX9705DEBC+T
6
6
V
1
2
3
4
5
10 PV
DD
DD
IN+
IN-
9
8
7
6
OUT-
OUT+
PGND
SYNC
MAX9705
12 UCSP-12
10 TDFN-10
10 µMAX
6
GND
SHDN
12
12
µMAX
12 UCSP-12
10 TDFN-10
10 µMAX
12
15.6
15.6
15.6
20
10
9
8
7
6
12 UCSP-12
10 TDFN-10
10 µMAX
20
MAX9705
12 UCSP-12
20
+
Ordering Information (continued)
1
2
3
4
5
PIN-
PACKAGE
TOP
MARK
PART
TEMP RANGE
TDFN
MAX9705CETB+T
MAX9705CEUB+
MAX9705CEBC+T
MAX9705DETB+T
MAX9705DEUB+
MAX9705DEBC+T
-40oC to +85oC 10 TDFN-10
-40oC to +85oC 10 µMAX
-40oC to +85oC 12 UCSP-12
-40oC to +85oC 10 TDFN-10
-40oC to +85oC 10 µMAX
-40oC to +85oC 12 UCSP-12
ACZ
—
TOP VIEW
MAX9705
2
(BUMP SIDE DOWN)
1
3
4
ACI
ADA
—
V
SYNC
PGND
OUT+
DD
A
B
IN+
SHDN
GND
PV
DD
ACJ
+Denotes lead-free package.
IN-
OUT-
C
UCSP
______________________________________________________________________________________ 15
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
System Diagram
V
DD
1µF
V
DD
0.1µF
2.2kΩ
V
DD
PV
DD
AUX_IN
BIAS
OUT+
IN+
MAX9705
IN-
OUT-
OUT
OUT
SHDN
SYNC
CODEC/
BASEBAND
PROCESSOR
2.2kΩ
0.1µF
MAX4063
IN+
IN-
V
DD
0.1µF
1µF
V
DD
SHDN
INL
1µF
1µF
OUTL
OUTR
MAX9722
INR
µCONTROLLER
PV
SV
SS
SS
C1P
CIN
1µF
1µF
Chip Information
TRANSISTOR COUNT: 3595
PROCESS: BiCMOS
16 ______________________________________________________________________________________
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio 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.)
PACKAGE OUTLINE, 4x3 UCSP
1
21-0104
F
1
______________________________________________________________________________________ 17
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio 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.)
D2
D
A2
PIN 1 ID
N
0.35x0.35
b
[(N/2)-1] x e
REF.
PIN 1
INDEX
AREA
E
E2
DETAIL A
e
A1
k
C
C
L
L
A
L
L
e
e
PACKAGE OUTLINE, 6,8,10 & 14L,
TDFN, EXPOSED PAD, 3x3x0.80 mm
1
-DRAWING NOT TO SCALE-
21-0137
G
2
18 ______________________________________________________________________________________
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio 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.)
COMMON DIMENSIONS
SYMBOL
MIN.
0.70
2.90
2.90
0.00
0.20
MAX.
0.80
3.10
3.10
0.05
0.40
A
D
E
A1
L
k
0.25 MIN.
0.20 REF.
A2
PACKAGE VARIATIONS
DOWNBONDS
ALLOWED
PKG. CODE
T633-1
N
6
D2
E2
e
JEDEC SPEC
MO229 / WEEA
MO229 / WEEA
MO229 / WEEC
MO229 / WEEC
MO229 / WEEC
b
[(N/2)-1] x e
1.90 REF
1.90 REF
1.95 REF
1.95 REF
1.95 REF
2.00 REF
2.40 REF
2.40 REF
1.50 0.10 2.30 0.10 0.95 BSC
1.50 0.10 2.30 0.10 0.95 BSC
1.50 0.10 2.30 0.10 0.65 BSC
1.50 0.10 2.30 0.10 0.65 BSC
1.50 0.10 2.30 0.10 0.65 BSC
0.40 0.05
0.40 0.05
0.30 0.05
0.30 0.05
0.30 0.05
NO
NO
T633-2
6
T833-1
8
NO
T833-2
8
NO
T833-3
8
YES
NO
T1033-1
T1433-1
T1433-2
10
14
14
1.50 0.10 2.30 0.10 0.50 BSC MO229 / WEED-3 0.25 0.05
1.70 0.10 2.30 0.10 0.40 BSC
1.70 0.10 2.30 0.10 0.40 BSC
- - - -
- - - -
0.20 0.05
0.20 0.05
YES
NO
PACKAGE OUTLINE, 6,8,10 & 14L,
TDFN, EXPOSED PAD, 3x3x0.80 mm
2
-DRAWING NOT TO SCALE-
21-0137
G
2
______________________________________________________________________________________ 19
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio 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.)
e
4X S
10
10
INCHES
MAX
MILLIMETERS
MAX
1.10
0.15
0.95
3.05
3.00
3.05
3.00
5.05
0.70
DIM MIN
MIN
-
A
-
0.043
0.006
0.037
0.120
0.118
0.120
0.118
0.199
A1
A2
D1
D2
E1
E2
H
0.002
0.030
0.116
0.114
0.116
0.114
0.187
0.05
0.75
2.95
2.89
2.95
2.89
4.75
0.40
H
Ø0.50 0.1
0.6 0.1
L
0.0157 0.0275
0.037 REF
L1
b
0.940 REF
0.007
0.0106
0.177
0.270
0.200
1
1
e
0.0197 BSC
0.500 BSC
0.6 0.1
c
0.0035 0.0078
0.0196 REF
0.090
BOTTOM VIEW
0.498 REF
S
α
TOP VIEW
0°
6°
0°
6°
D2
E2
GAGE PLANE
A2
c
A
E1
b
L
α
A1
D1
L1
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE, 10L uMAX/uSOP
APPROVAL
DOCUMENT CONTROL NO.
REV.
1
21-0061
I
1
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.
20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2005 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
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