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PDF MAX9712 Data sheet ( Hoja de datos )
| Número de pieza | MAX9712 | |
| Descripción | Class D Audio Amplifier | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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19-2917; Rev 1; 1/04
500mW, Low EMI, Filterless,
Class D Audio Amplifier
General Description
The MAX9712 mono class D audio power amplifier pro-
vides class AB amplifier performance with class D effi-
ciency, conserving board space, and extending battery
life. Using a class D architecture, the MAX9712 delivers
up to 500mW into an 8Ω load while offering efficiencies
above 85%. A patented, low EMI modulation scheme
renders the traditional class D output filter unnecessary.
www.DataSheet4U.com
The MAX9712 offers two modulation schemes: a fixed-
frequency (FFM) mode, and a spread-spectrum (SSM)
mode that reduces EMI-radiated emissions due to the
modulation frequency. Furthermore, the MAX9712 oscil-
lator can be synchronized to an external clock through
the SYNC input, allowing the switching frequency to be
user defined. The SYNC input also allows multiple
MAX9712s to be cascaded and frequency locked, mini-
mizing interference due to clock intermodulation. The
device utilizes a fully differential architecture, a full-
bridged output, and comprehensive click-and-pop sup-
pression. The gain is internally set to +4V/V, further
reducing external component count.
The MAX9712 features high 72dB PSRR, a low 0.01%
THD+N, and SNR in excess of 90dB. Short-circuit and
thermal-overload protection prevent the device from
damage during a fault condition. The MAX9712 is avail-
able in 10-pin TDFN (3mm ✕ 3mm ✕ 0.8mm), 10-pin
µMAX, and 12-bump UCSP™ (1.5mm ✕ 2mm ✕ 0.6mm)
packages. The MAX9712 is specified over the extended
-40°C to +85°C temperature range.
Cellular Phones
PDAs
Applications
MP3 Players
Portable Audio
Simplified Block Diagram
Features
♦ Filterless Amplifier Passes FCC Radiated
Emissions Standards with 100mm of Cable
♦ Unique Spread-Spectrum Mode Offers 5dB
Emissions Improvement Over Conventional
Methods
♦ Optional External SYNC Input
♦ Simple Master-Slave Setup for Stereo Operation
♦ 85% Efficiency
♦ Up to 500mW into 8Ω
♦ Low 0.01% THD+N
♦ High PSRR (72dB at 217Hz)
♦ Integrated Click-and-Pop Suppression
♦ Low Quiescent Current (4mA)
♦ Low-Power Shutdown Mode (0.1µA)
♦ Short-Circuit and Thermal-Overload Protection
♦ Available in Thermally Efficient, Space-Saving
Packages
10-Pin TDFN (3mm ✕ 3mm ✕ 0.8mm)
10-Pin µMAX
12-Bump UCSP (1.5mm ✕ 2mm ✕ 0.6mm)
PART
MAX9712ETB
MAX9712EUB
MAX9712EBC-T
Ordering Information
TEMP RANGE
PIN/BUMP-
PACKAGE
-40°C to +85°C 10 TDFN
-40°C to +85°C 10 µMAX
-40°C to +85°C 12 UCSP-12
TOP
MARK
AAI
—
ABN
VDD Pin Configurations
DIFFERENTIAL
AUDIO INPUT
SYNC
INPUT
MODULATOR
AND H-BRIDGE
OSCILLATOR
MAX9712
TOP VIEW
VDD 1
IN+ 2
IN- 3
GND 4
SHDN 5
MAX9712
10 PVDD
9 OUT-
8 OUT+
7 PGND
6 SYNC
UCSP is a trademark of Maxim Integrated Products, Inc.
TDFN/µMAX
Pin Configurations continued at end of data sheet.
________________________________________________________________ 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.
1 page  
500mW, Low EMI, Filterless,
Class D Audio Amplifier
Typical Operating Characteristics (continued)
(VDD = 3.3V, VSYNC = GND, TA = +25°C, unless otherwise noted.)
EFFICIENCY vs. SUPPLY VOLTAGE
100
90
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70
RL = 6Ω RL = 8Ω
RL = 16Ω
60
50
40
30
20
10
f = 1kHz
0
2.5 3.0
3.5 4.0 4.5
SUPPLY VOLTAGE (V)
5.0
5.5
100
90
80
70
60
50
40
30
20
10
0
800
EFFICIENCY
vs. SYNC INPUT FREQUENCY
VDD = 3.3V
f = 1kHz
POUT = 300mW
RL = 8Ω
1000 1200 1400 1600 1800 2000
SYNC FREQUENCY (kHz)
OUTPUT POWER
vs. SUPPLY VOLTAGE
1000
f = 1kHz
900
800
700 RL = 16Ω
600
500
400
300 RL = 8Ω
200
100
0
2.5
RL = 6Ω
3.1 3.7 4.3 4.9
SUPPLY VOLTAGE (V)
5.5
OUTPUT POWER
vs. LOAD RESISTANCE
1000
f = 1kHz
900 THD+N = 1%
800
700 VDD = 5V
600
500 VDD = 3.3V
400
300
200
100
0
0 10 20 30 40 50 60 70 80 90 100
LOAD RESISTANCE (Ω)
COMMON-MODE REJECTION RATIO
vs. FREQUENCY
0
-10 INPUT REFERRED
VIN = 200mVP-P
-20
-30
-40
-50
-60
-70
-80
-90
-100
10
100 1k 10k
FREQUENCY (Hz)
100k
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
0
-10 OUTPUT REFERRED
INPUTS AC GROUNDED
-20 VDD = 3.3V
-30
-40
-50
-60
-70
-80
-90
-100
10
100 1k 10k
FREQUENCY (Hz)
100k
GSM POWER-SUPPLY REJECTION
MAX9712TOC19
VDD 500mV/div
OUTPUT FREQUENCY SPECTRUM
0
FFM MODE
-20 VOUT = -60dBV
f = 1kHz
-40
RL = 8Ω
UNWEIGHTED
-60
-80
MAX9712
OUTPUT
100µV/div
-100
-120
f = 217Hz
2ms/div
DUTY CYCLE = 88%
INPUT LOW = 3V
RL = 8Ω
INPUT HIGH = 3.5V
-140
0
5k 10k 15k
FREQUENCY (Hz)
20k
_______________________________________________________________________________________ 5
5 Page 
500mW, Low EMI, Filterless,
Class D Audio Amplifier
50.0
45.0
40.0
35.0
30.0
www.DataSheet4U2.5c.0om
20.0
15.0
10.0
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)
VIN = 0V
OUT-
OUT+
Figure 3. MAX9712 with 76mm of Speaker Cable
VOUT+ - VOUT- = 0V
Figure 4. MAX9712 Outputs with No Input Signal
Shutdown
The MAX9712 has a shutdown mode that reduces power
consumption and extends battery life. Driving SHDN low
places the MAX9712 in a low-power (0.1µA) shutdown
mode. Connect SHDN to VDD for normal operation.
Click-and-Pop Suppression
The MAX9712 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 35ms following startup, a soft-start
function gradually unmutes the input amplifiers.
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. The traditional PWM
scheme uses large differential output swings (2 x VDD
peak-to-peak) and causes large ripple currents. Any
parasitic resistance in the filter components results in a
loss of power, lowering the efficiency.
The MAX9712 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.
EFFICIENCY vs. OUTPUT POWER
100
90
80
70
60 MAX9712
50
40
CLASS AB
30
20
10
0
0
VDD = 3.3V
f = 1kHz
RL - 8Ω
0.1 0.2 0.3 0.4
OUTPUT POWER (W)
0.5
Figure 5. MAX9712 Efficiency vs. Class AB Efficiency
Because the frequency of the MAX9712 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 may be dam-
aged. For optimum results, use a speaker with a series
inductance >10µH. Typical 8Ω speakers exhibit series
inductances in the range of 20µH to 100µH.
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
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet MAX9712.PDF ] | |
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