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19-3405; Rev 3; 5/09
KIT
ATION
EVALU
BLE
AVAILA
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
General Description
Features
♦
Filterless Amplifier Passes FCC-Radiated
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
OUT
= 1W, V
DD
= 5.0V)
♦
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
♦
Available in Thermally Efficient, Space-Saving
Packages
10-Pin TDFN (3mm x 3mm x 0.8mm)
12-Bump UCSP (1.5mm x 2mm x 0.6mm)
♦
Pin-for-Pin Compatible with the MAX9700 and
MAX9712
MAX9705
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 spread-spectrum
modulation scheme eliminates the need for output filter-
ing found in traditional Class D devices. These design
concepts reduce an application’s component count and
extend battery life.
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.
The MAX9705 is available in 10-pin TDFN (3mm x 3mm x
0.8mm), 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.
Ordering Information
PART
MAX9705AETB+T
MAX9705AEBC+T
MAX9705BETB+T
TEMP RANGE
-40
o
C to +85
o
C
-40 C to +85 C
-40
o
C to +85
o
C
o
o
o
o
PIN-
PACKAGE
10 TDFN
12 UCSP
10 TDFN
TOP
MARK
ACY
ACH
ACX
MAX9705BEBC+T
-40 C to +85 C 12 UCSP
ACG
Ordering Information continued at end of data sheet.
+Denotes
a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
Applications
Cellular Phones
PDAs
MP3 Players
Portable Audio
AMPLITUDE (dBμV/m)
50.0
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
30.0
FCC EMI LIMIT
EMI Spectrum Diagram
Selector Guide appears at end of data sheet.
UCSP is a trademark of Maxim Integrated Products, Inc.
MAXIM'S NEW ULTRA-LOW
OUTPUT SPECTRUM
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)
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim 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
MAX9705
ABSOLUTE MAXIMUM RATINGS
V
DD
to GND..............................................................................6V
PV
DD
to PGND .........................................................................6V
GND to PGND .......................................................-0.3V to +0.3V
PV
DD
to V
DD
..........................................................-0.3V to +0.3V
All Other Pins to GND.................................-0.3V to (V
DD
+ 0.3V)
Continuous Current Into/Out of PV
DD
/PGND/OUT_........±600mA
Continuous Input Current (all other pins) .........................±20mA
Duration of OUT_ Short Circuit to GND or PV
DD
........Continuous
Duration of Short Circuit Between OUT+ and OUT-.....Continuous
Continuous Power Dissipation (T
A
= +70°C)
10-Pin TDFN (derate 24.4mW/°C above +70°C) .....1951.2mW
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)
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
DD
= PV
DD
= V
SHDN
= 3.3V,
V
GND
= V
PGND
= 0, SYNC = GND (FFM), R
L
=
∞,
R
L
connected between OUT+ and OUT-,
T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Notes 1, 2)
PARAMETER
GENERAL
Supply Voltage Range
Quiescent Current
Shutdown Current
Turn-On Time
Input Resistance
V
DD
I
DD
I
SHDN
t
ON
R
IN
V
BIAS
T
A
= +25°C
Either input
MAX9705A
MAX9705B
MAX9705C
MAX9705D
12
0.88
0.73
0.61
0.48
1.9
3.8
5.7
9.5
Inferred from PSRR test
2.5
5.4
0.3
30
20
1.0
0.83
0.71
0.56
2.0
4.0
6.0
10
±10
56
50
75
75
60
600
950
mW
dB
1.12
0.93
0.81
0.64
2.1
4.2
6.3
10.5
±69
mV
dB
5.5
7
10
V
mA
µA
ms
kΩ
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Input Bias Voltage
V
MAX9705A
Voltage Gain
A
V
MAX9705B
MAX9705C
MAX9705D
Output Offset Voltage
Common-Mode Rejection Ratio
Power-Supply Rejection Ratio
(Note 3)
V
OS
CMRR
PSRR
T
A
= +25°C
f
IN
= 1kHz, input referred
V
DD
= 2.5V to 5.5V, T
A
= +25°C
200mV
P-P
ripple
f
RIPPLE
= 217Hz
f
RIPPLE
= 20kHz
R
L
= 8Ω
Output Power
P
OUT
THD+N = 1%,
f
IN
= 1kHz
R
L
= 4Ω
MAX9705_ETB+T and
MAX9705_EUB+ only
R
L
= 8Ω,
P
OUT
= 450mW
R
L
= 4Ω,
P
OUT
= 375mW
Into shutdown
Out of shutdown
V/V
Total Harmonic Distortion
Plus Noise
THD+N
f
IN
= 1kHz, either
FFM or SSM
Peak voltage,
A-weighted
(Notes 3, 4)
0.02
%
0.025
-68
dB
-60.5
176
V/µs
Click/Pop Level
Output Slew Rate
K
CP
SR
2
_______________________________________________________________________________________
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= PV
DD
= V
SHDN
= 3.3V,
V
GND
= V
PGND
= 0, SYNC = GND (FFM), R
L
=
∞,
R
L
connected between OUT+ and OUT-,
T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Notes 1, 2)
PARAMETER
Rise/Fall Time
SYMBOL
t
RISE
, t
FALL
10% to 90%
BW = 22Hz
to 22kHz
A-weighted
SYNC = GND
Oscillator Frequency
SYNC Frequency Lock Range
Efficiency
DIGITAL INPUTS (SHDN, SYNC)
Input Thresholds
SHDN
Input Leakage Current
SYNC Input Current
(Note 5)
V
IH
V
IL
0.1
-1.25
2
0.8
±10
±10
V
µA
µA
η
P
OUT
= 800mW, f
IN
= 1kHz, R
L
= 8Ω
f
OSC
SYNC = V
DD
(SSM mode)
800
89
FFM
SSM
FFM
SSM
980
CONDITIONS
MIN
TYP
15
91
89
93
91
1100
1220
±120
2000
1220
kHz
kHz
%
dB
MAX
UNITS
ns
MAX9705
Signal-to-Noise Ratio
SNR
V
OUT
= 2V
RMS
ELECTRICAL CHARACTERISTICS
(V
DD
= PV
DD
= V
SHDN
= 5V,
V
GND
= V
PGND
= 0, SYNC = GND (FFM), R
L
=
∞,
R
L
connected between OUT+ and OUT-,
T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Notes 1, 2)
PARAMETER
Quiescent Current
Shutdown Current
Power-Supply Rejection Ratio
SYMBOL
I
DD
I
SHDN
PSRR
200mV
P-P
ripple
f = 217Hz
f = 20kHz
R
L
= 16Ω
Output Power
P
OUT
THD+N = 1%,
f = 1kHz
R
L
= 8Ω
R
L
= 4Ω
MAX9705_ETB+T and
MAX9705_EUB+ only
R
L
= 8Ω, P
OUT
= 1.0W
R
L
= 4Ω, P
OUT
= 1.75W
FFM
SSM
FFM
SSM
CONDITIONS
MIN
TYP
7
0.55
75
60
750
1400
mW
2300
0.02
0.05
94
91
97
93
dB
MAX
UNITS
mA
µA
dB
Total Harmonic Distortion
Plus Noise
THD+N
f = 1kHz, either
FFM or SSM
V
OUT
=
3V
RMS
%
Signal-to-Noise Ratio
SNR
BW = 22Hz to
22kHz
A-weighted
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
L
= 4Ω, L = 33µH.
For R
L
= 8Ω, L = 68µH. For R
L
= 16Ω, L = 136µH.
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
CP
level is calculated as 20 x log[(peak voltage under normal operation at rated power
level)/(peak voltage during mode transition, no input signal)]. Units are expressed in dB.
Note 5:
SYNC has a 1MΩ resistor to V
REF
= 1.25V.
_______________________________________________________________________________________
3
2.3W, Ultra-Low-EMI, Filterless,
Class D Audio Amplifier
MAX9705
Typical Operating Characteristics
(V
DD
= 3.3V, SYNC = V
DD
(SSM), differential input, T
A
= +25°C, unless otherwise noted.
Typical Operating Characteristics
for 4Ω
load condition apply to the MAX9705_ETB+T only.)
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9705toc01
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9705toc02
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9705toc03
100
f
IN
= 1kHz
100
100
10
10
10
THD+N (%)
THD+N (%)
THD+N (%)
1
1
1
0.1
0.1
0.1
0.01
V
DD
= 3.3V
R
L
= 8Ω
0.001
0
0.2
0.4
0.6
0.8
1.0
1.2
OUTPUT POWER (W)
0.01
f
IN
= 1kHz
0.001
0
0.5
1.0
OUTPUT POWER (W)
1.5
2.0
V
DD
= 5.0V
R
L
= 8Ω
0.01
0.001
0
0.2
f
IN
= 1kHz
V
DD
= 2.5V
R
L
= 4Ω
0.4
OUTPUT POWER (W)
0.6
0.8
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9705toc04
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX9705toc05
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
V
DD
= 3.3V
R
L
= 8Ω
f
IN
= 1kHz
MAX9705toc06
100
100
100
10
10
10
THD+N (%)
1
THD+N (%)
THD+N (%)
1
1
SSM
0.1
FFM
0.1
0.1
0.01
0.001
0
0.5
f
IN
= 1kHz
0.01
V
DD
= 3.3V
R
L
= 4Ω
0.001
1.0
1.5
0
0.5
1.0
1.5
2.0
2.5
3.0
f
IN
= 1kHz
V
DD
= 5.0V
R
L
= 4Ω
0.01
0.001
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
MAX9705toc07
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX9705toc08
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
V
DD
= 2.5V
R
L
= 4Ω
MAX9705toc09
100
V
DD
= 3.3V
R
L
= 8Ω
10
THD+N (%)
100
V
DD
= 5.0V
R
L
= 8Ω
10
THD+N (%)
100
10
THD+N (%)
P
OUT
= 50mW
1
P
OUT
= 300mW
0.1
1
P
OUT
= 100mW
1
P
OUT
= 250mW
0.1
P
OUT
= 450mW
0.1
P
OUT
= 1W
0.01
10
100
1k
FREQUENCY (Hz)
10k
100k
0.01
10
100
1k
FREQUENCY (Hz)
10k
100k
0.01
10
100
1k
FREQUENCY (Hz)
10k
100k
4
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