MAX9756 [MAXIM]
2.3W Stereo Speaker Amplifiers and DirectDrive Headphone Amplifiers with Automatic Level Control;型号: | MAX9756 |
厂家: | MAXIM INTEGRATED PRODUCTS |
描述: | 2.3W Stereo Speaker Amplifiers and DirectDrive Headphone Amplifiers with Automatic Level Control |
文件: | 总31页 (文件大小:790K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
19-3782; Rev 1; 1/06
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
General Description
Features
♦ Automatic Level Control—Protects Speakers
The MAX9756/MAX9757/MAX9758 combine dual, 2.3W,
bridge tied load (BTL) stereo audio power amplifiers and
a DirectDriveTM headphone amplifier in a single device.
These devices feature single-supply voltage operation,
shutdown mode, logic-selectable gain, a headphone
sense input, a 31-step analog volume control, and indus-
try-leading click-and-pop suppression. The headphone
amplifier uses Maxim’s DirectDrive architecture that pro-
duces a ground-referenced output from a single supply,
eliminating the need for large DC-blocking capacitors.
♦ Analog Volume Control
♦ 120mW DirectDrive Headphone Amplifiers (16Ω)
♦ 150mA Adjustable LDO
♦ Class AB, 2.3W, Stereo BTL Speaker Amplifiers
(3Ω)
♦ High 95dB PSRR
♦ Low-Power Shutdown Mode
♦ Industry-Leading Click-and-Pop Suppression
♦ Short-Circuit and Thermal Protection
♦ Beep Input
The MAX9756/MAX9757 feature automatic level control
(ALC) that automatically limits output power to the speak-
er in the event of an overpowered output.
The MAX9756/MAX9758s’ 150mA internal linear regula-
tor provides a complete solution for DAC- or CODEC-
based designs.
The MAX9756/MAX9757/MAX9758 are offered in space-
saving, thermally efficient 32-pin (5mm x 5mm x 0.8mm)
and 36-pin thin QFN (6mm x 6mm x 0.8mm) packages.
All devices are specified over the extended -40°C to
+85°C temperature range.
Ordering Information
PART
ALC
√
LDO
√
PIN-PACKAGE
36 Thin QFN-EP*
32 Thin QFN-EP*
32 Thin QFN-EP*
MAX9756ETX+
MAX9757ETJ+
MAX9758ETJ+
√
—
√
—
Applications
Note: All devices specified for -40°C to +85°C operating
Notebook PCs
Tablet PCs
Flat-Panel TVs
PC Displays
temperature range.
+Denotes lead-free package.
*EP = Exposed paddle.
Portable DVD
Players
LCD Projectors
Portable Audio
Simplified Block Diagrams
SINGLE SUPPLY 4.5V TO 5.5V
ALC
SINGLE SUPPLY 4.5V TO 5.5V
SINGLE SUPPLY 4.5V TO 5.5V
ALC
ALC
ALC
VOL
BEEP
HPS
VOL
BEEP
HPS
VOL
BEEP
HPS
1.2V TO 5V
LDO
1.2V TO 5V
LDO
MAX9757
MAX9756
MAX9758
________________________________________________________________ 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 Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (V , PV , HPV , CPV , IN to GND) ....+6V
Continuous Input Current (all other pins) ......................... 20mA
DD
DD
DD
DD
PGND, CPGND to GND...................................................... 0.3V
CPV , C1N, V to GND......................................-6.0V to +0.3V
Continuous Power Dissipation (T = +70°C, single-layer board)
A
32-Pin Thin QFN (derate 18.6mW/°C above +70°C).....1490mW
36-Pin Thin QFN (derate 20.4mW/°C above +70°C).....1633mW
Continuous Power Dissipation (T =+70°C, multilayer board)
A
32-Pin Thin QFN (derate 24.9mW/°C above +70°C).....1990mW
36-Pin Thin QFN (derate 27.7mW/°C above +70°C).....2180mW
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
SS
SS
HP_ to GND ........................................................................... 3V
Any Other Pin .............................................-0.3V to (V + 0.3V)
DD
Duration of OUT_ Short Circuit to GND or PV ........Continuous
DD
Duration of OUT_+ Short Circuit to OUT_-.................Continuous
Duration of HP_ Short Circuit to GND,
V , or HPV .........................................................Continuous
SS DD
Duration of OUT Short Circuit to GND........................Continuous
Continuous Current (PV , OUT_, PGND) ...........................1.7A
DD
Continuous Current (CPV , C1N, CPGND, C1P, CPV
,
SS
DD
V
SS
, HPV , HP_, IN, OUT).............................................0.85A
DD
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 = PV
= HPV
= CPV = IN = +5.0V, GND = PGND = CPGND = 0, SHDN = V , REGEN = V , DR = SET = GND, C
DD
DD
DD DD DD DD BIAS
= 1µF, C
= 1µF, C1 = C2 = 1µF, PREF = unconnected, speaker loads terminated between OUT_+ and OUT_-, headphone load
PVSS
terminated between HP_ and GND, GAIN1 = GAIN2 = GAIN3 = VOL = 0 (A
= 15dB, A
= 0dB), T = -40°C to +85°C, unless
V(HP) A
V(SP)
otherwise noted. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
GENERAL
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Voltage Range
V
, PV
Inferred from PSRR test
4.5
3.0
5.5
5.5
V
V
DD
DD
Headphone Supply Voltage
HPV
Inferred from PSRR test
DD
HPS = GND, speaker
14
7
29
13
mode, R = ∞
I
I
= I
HPVDD
+
L
DD
VDD
+ I
Quiescent Supply Current
I
mA
DD
HPS = 5V, headphone
CPVDD
mode, R = ∞
L
Shutdown Supply Current
Bias Voltage
I
SHDN = REGEN = GND
0.2
2.43
10
5
µA
V
SHDN
V
2.2
10
2.65
BIAS
Switching Time
t
Gain or input switching
INL and INR
µs
kΩ
ms
SW
Input Resistance
Turn-On Time
R
20
30
15
IN
t
25
SON
SPEAKER AMPLIFIERS (HPS = GND)
Measured between OUT_+ and OUT_-,
Output Offset Voltage
V
0.4
mV
dB
OS
T
A
= +25°C
PV
= 4.5V to 5.5V, T = +25°C
75
95
83
DD
A
Power-Supply Rejection Ratio
(Note 2)
PSRR
f = 1kHz, V
= 200mV
RIPPLE
P-P
f = 10kHz, V
= 200mV
68
RIPPLE
P-P
R = 8Ω
0.9
1.3
L
THD+N = 1%, f = 1kHz
(T = +25°C)
R = 4Ω
L
2.0
Output Power (Note 3)
P
W
OUT
A
R = 3Ω
L
2.3
R = 8Ω, BTL P
= 1W, f = 1kHz
0.009
0.015
L
OUT
OUT
OUT
Total Harmonic Distortion Plus
Noise
THD+N
SNR
%
R = 4Ω, BTL P
L
= 1W, f = 1kHz
R = 8Ω, BTL P
= 1W, BW = 22Hz to
L
92
95
22kHz, unweighted
Signal-to-Noise Ratio
dB
R = 8Ω, BTL P
L
= 1W, A weighted
OUT
2
_______________________________________________________________________________________
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
ELECTRICAL CHARACTERISTICS (continued)
(V = PV
= HPV
= CPV = IN = +5.0V, GND = PGND = CPGND = 0, SHDN = V , REGEN = V , DR = SET = GND, C
DD
DD
DD DD DD DD BIAS
= 1µF, C
= 1µF, C1 = C2 = 1µF, PREF = unconnected, speaker loads terminated between OUT_+ and OUT_-, headphone load
PVSS
terminated between HP_ and GND, GAIN1 = GAIN2 = GAIN3 = VOL = 0 (A
= 15dB, A
= 0dB), T = -40°C to +85°C, unless
V(HP) A
V(SP)
otherwise noted. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
µV
BW = 22Hz to 22kHz, unweighted,
measured at output, input at AC GND
Noise
V
71
n
RMS
Capacitive-Load Drive
Crosstalk
C
No sustained oscillations
200
80
pF
dB
L
L to R, R to L, f = 10kHz
Slew Rate
SR
Measured between OUT_+ and OUT_-
1.3
V/µs
GAIN3 = 0
GAIN3 = 0
GAIN3 = 0
GAIN3 = 0
GAIN3 = 1
GAIN3 = 1
GAIN3 = 1
GAIN3 = 1
GAIN2 = 0
GAIN2 = 0
GAIN2 = 1
GAIN2 = 1
GAIN2 = 0
GAIN2 = 0
GAIN2 = 1
GAIN2 = 1
GAIN1 = 0
GAIN1 = 1
GAIN1 = 0
GAIN1 = 1
GAIN1 = 0
GAIN1 = 1
GAIN1 = 0
GAIN1 = 1
15
16.5
18
19.5
21
Gain (Maximum Volume Settings)
(Note 4)
A
VMAX
(SPKR)
dB
22.5
24.0
25.5
Into
shutdown
Out of
shutdown
65
Peak voltage, 32
samples/second,
A weighted (Note 5)
Click-and-Pop Level
K
dBV
CP
38.5
HEADPHONE AMPLIFIERS (HPS = V
)
DD
Output Offset Voltage
V
T
= +25°C
2
90
7
mV
dB
OS(HP)
A
HPV
= 3V to 5.5V, T = +25°C
70
40
DD
A
Power-Supply Rejection Ratio
(Note 2)
PSRR
f = 1kHz, V
= 200mV
72
RIPPLE
P-P
f = 10kHz, V
= 200mV
70
RIPPLE
P-P
R = 32Ω
L
68
THD+N = 1%, f = 1kHz
(T = +25°C)
Output Power (Note 3)
P
mW
%
OUT
A
R = 16Ω
L
130
0.02
0.04
R = 32Ω, V
= 1V
= 1V
, f = 1kHz
, f = 1kHz
L
OUT
RMS
Total Harmonic Distortion Plus
Noise
THD+N
SNR
R = 16Ω, V
L
OUT
RMS
R = 32Ω, BTL P
BW = 22Hz to 22kHz, unweighted
= 65mW,
L
OUT
97
Signal-to-Noise Ratio
dB
R = 32Ω, BTL P = 65W,
BW = 22Hz to 22kHz, A weighted
L
OUT
100
Noise
V
BW = 22Hz to 22kHz
20.4
200
60
µV
RMS
n
Capacitive-Load Drive
Crosstalk
C
No sustained oscillations
L to R, R to L, f = 10kHz
pF
dB
L
Slew Rate
SR
1.4
0
V/µs
GAIN2 = 0, HPS = 1
GAIN2 = 1, HPS = 1
Gain (Maximum Volume Settings)
(Note 6)
A
dB
VMAX(HP)
3.0
Peak voltage, 32
samples/second,
A weighted (Note 4)
Into shutdown
Out of shutdown
62
50
Click-and-Pop Level
K
dBV
CP
_______________________________________________________________________________________
3
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
ELECTRICAL CHARACTERISTICS (continued)
(V = PV
= HPV
= CPV = IN = +5.0V, GND = PGND = CPGND = 0, SHDN = V , REGEN = V , DR = SET = GND, C
DD
DD
DD DD DD DD BIAS
= 1µF, C
= 1µF, C1 = C2 = 1µF, PREF = unconnected, speaker loads terminated between OUT_+ and OUT_-, headphone load
PVSS
terminated between HP_ and GND, GAIN1 = GAIN2 = GAIN3 = VOL = 0 (A
= 15dB, A
= 0dB), T = -40°C to +85°C, unless
V(HP) A
V(SP)
otherwise noted. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
CHARGE PUMP
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Charge-Pump Frequency
VOLUME CONTROL
VOL Input Impedance
VOL Input Hysteresis
f
500
550
600
kHz
OSC
R
100
10
MΩ
VOL
mV
0.858 x
Full Mute Voltage
(Note 7)
= 1kHz
V
HPV
DD
Full Mute Attenuation
Input Impedance
f
-85
dB
IN
R
VOL_
Any gain setting
100
0.2
0.3
1.0
MΩ
A
V
A
V
A
V
= +15dB to 0dB
= -2dB to -20dB
= -22dB to -56dB
Channel Matching
dB
BEEP INPUT
T
= +25°C, R = 47kΩ (see BEEP Input
B
A
Beep Signal Amplitude Threshold
0.3
V
section)
Beep Signal Frequency
Threshold
T
A
= +25°C
300
Hz
AUTOMATIC LEVEL CONTROL SPEAKER AMPLIFIER (MAX9756/MAX9757)
PREF Threshold Accuracy
Maximum Gain Compression
Attack Time
R
= 180kΩ
5
8.1
%
PREF
6.0
6.3
15
50
30
9.5
3
dB
ms
ms
C = 1µF (Note 8)
T
Hold Time
Time between attack and release phases
0V < V < (0.3V x V
)
DR
DD
C = 1µF,
T
release from
6dB
Release Time (Note 9)
0.4V < V < (0.6V x V
)
s
DR
DD
0.8V < V < V
DR
DD
DR INPUT (TRI-STATE INPUT)
0.8 x
DR Input Voltage High
V
V
V
V
DRH
DD
V
DD
0.4 x
0.6 x
V
DD
DR Input Voltage Middle
V
DRM
V
DD
0.3 x
DR Input Voltage Low
Input Leakage Current
V
0
V
DRL
V
DD
0V ≤ V ≤ V
1
µA
DR
DD
LOGIC INPUTS (GAIN_, SHDN, REGEN)
Input High Voltage
Input Low Voltage
Input Leakage Current
V
2
V
V
IH
V
0.8
1
IL
I
µA
IN
4
_______________________________________________________________________________________
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
ELECTRICAL CHARACTERISTICS (continued)
(V = PV
= HPV
= CPV = IN = +5.0V, GND = PGND = CPGND = 0, SHDN = V , REGEN = V , DR = SET = GND, C
DD
DD
DD DD DD DD BIAS
= 1µF, C
= 1µF, C1 = C2 = 1µF, PREF = unconnected, speaker loads terminated between OUT_+ and OUT_-, headphone load
PVSS
terminated between HP_ and GND, GAIN1 = GAIN2 = GAIN3 = VOL = 0 (A
= 15dB, A
= 0dB), T = -40°C to +85°C, unless
V(HP) A
V(SP)
otherwise noted. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
LOGIC INPUT HEADPHONE (HPS)
Input High Voltage
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
2
V
V
IH
Input Low Voltage
V
0.8
IL
HPS Pullup Current
35
µA
LOW-DROPOUT LINEAR REGULATOR
Input Voltage Range
V
Inferred from line regulation
3.5
5.5
V
IN
I
I
= 0mA, SHDN = GND
100
350
0.1
160
OUT
OUT
Supply (Ground) Current
I
µA
Q
= 150mA
Shutdown Current
Output Current
I
REGEN = 0V
3
µA
SHDN
I
150
mA
OUT
Fixed Output Voltage Accuracy
Adjustable Output Voltage Range
SET Reference Voltage
I
= 1mA
1.5
4.85
1.23
%
V
OUT
V
SET
V
1.19
1.21
200
20
V
SET
SET Dual-Mode Threshold
SET Input Leakage Current
mV
nA
I
500
50
SET
I
I
= 50mA
25
OUT
V
= 4.65V (fixed
OUT
Dropout Voltage (Note 10)
∆V
mV
OD
output operation)
= 150mA
100
300
20
150
OUT
Output Current Limit
Startup Time
I
mA
µs
LIM
V
= 3.5V to 5.5V, V
= 1mA
= 2.5V,
IN
OUT
Line Regulation
Load Regulation
Ripple Rejection
-0.1
+0.01
+0.1
%/V
%
I
OUT
V
V
= 4.65V, 1mA < I
< 150mA
0.5
60
50
OUT
OUT
f = 1kHz
f = 10kHz
= 200mV
dB
RIPPLE
P-P
20Hz to 22kHz, C
= 2 x 1µF,
= 4.65V
OUT
Output Voltage Noise
100
µV
RMS
I
= 150mA, V
OUT
OUT
Note 1: All devices are 100% production tested at room temperature. All temperature limits are guaranteed by design.
Note 2: PSRR is specified with the amplifier input connected to GND through R and C
.
IN
IN
Note 3: Output power levels are measured with the TQFN’s exposed paddle soldered to the ground plane.
Note 4: Speaker path gain is defined as: A = (V - V )/V ).
VSPKR
OUT+
OUT- IN__
Note 5: Speaker mode testing performed with 8Ω resistive load connected across BTL output. Headphone mode testing per-
formed with 32Ω resistive load connected between HP_ and GND. Mode transitions are controlled by SHDN.
Note 6: Headphone path gain is defined as: A
= V
/V
.
VHP
HP_ IN__
Note 7: See Table 3 for detains on the mute levels.
Note 8: Attack envelope is exponential. Attack time is defined as the 15 x 103 x C .
T
Note 9: Time for the gain to return to within 10% of nominal gain setting after the input signal has fallen below the PREF threshold.
Release is linear in dB. Release time is proportional to magnitude of gain compression.
Note 10: Dropout voltage is defined as (V - V
) when V
is 2% below the value of V
for V = V
+ 1V.
OUT(NOM)
IN
OUT
OUT
OUT
IN
_______________________________________________________________________________________
5
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
Typical Operating Characteristics
(V
= PV
= HPV
= CPV
= IN = +5.0V, GND = PGND = CPGND = 0V, SHDN = V , REGEN = DR = SET = GND, C
=
DD
DD
DD
DD
DD
BIAS
1µF, C
= 1µF, C1 = C2 = 1µF, PREF = unconnected, GAIN1 = 1, GAIN2 = GAIN3 = VOL = 0V, measurement BW = 22Hz to
PVSS
22kHz, T = +25°C, unless otherwise noted.)
A
TOTAL HARMONIC DISTORTION PLUS NOISE
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (HEADPHONE MODE)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (HEADPHONE MODE)
vs. FREQUENCY (HEADPHONE MODE)
10
10
10
V
= 5V
V
= 5V
V
= 5V
DD
DD
DD
R = 3Ω
L
R = 4Ω
L
R = 8Ω
L
1
0.1
1
1
0.1
0.1
OUTPUT POWER = 500mW
OUTPUT POWER = 500mW
OUTPUT POWER = 500mW
0.01
0.001
0.01
0.001
0.01
0.001
OUTPUT POWER = 1.8W
OUTPUT POWER = 1.5W
OUTPUT POWER = 1W
10
100
1k
10k
100k
10
100
1k
10k
100k
10
100
1k
10k
100k
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (SPEAKER MODE)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (SPEAKER MODE)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (SPEAKER MODE)
100
100
100
V
= 5V
V
= 5V
DD
V
= 5V
DD
DD
R = 3Ω
L
R = 8Ω
L
R = 4Ω
L
10
10
10
1
1
1
f
= 10kHz
f
= 10kHz
IN
IN
f
= 10kHz
IN
0.1
0.1
0.1
0.01
0.001
0.01
0.001
0.01
0.001
f
= 100Hz
IN
f
= 1kHz
f
= 1kHz
IN
f = 100Hz
IN
IN
f
= 1kHz
0.5
f
= 100Hz
1.5
IN
IN
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5
OUTPUT POWER (W)
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5
OUTPUT POWER (W)
0
1.0
2.0
OUTPUT POWER (W)
POWER DISSIPATION vs. OUTPUT POWER
(SPEAKER MODE)
OUTPUT POWER
vs. LOAD RESISTANCE (SPEAKER MODE)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY (SPEAKER MODE)
3.0
2.5
2.0
1.5
1.0
0.5
0
3.0
2.5
2.0
1.5
1.0
0.5
0
0
-10
R = 4Ω
L
V
= 200mV
RIPPLE P-P
V
= 5V
DD
R = 8Ω
L
f = 1kHz
-20
-30
-40
THD+N = 10%
-50
R = 8Ω
L
-60
-70
-80
THD+N = 1%
-90
-100
-110
-120
f = 1kHz
P
= P
+ P
OUTL OUTR
OUT
1
10
LOAD RESISTANCE (Ω)
100
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
OUTPUT POWER (W)
10
100
1k
FREQUENCY (Hz)
10k
100k
6
_______________________________________________________________________________________
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
Typical Operating Characteristics (continued)
(V
= PV
= HPV
= CPV
= IN = +5.0V, GND = PGND = CPGND = 0V, SHDN = V , REGEN = DR = SET = GND, C
=
DD
DD
DD
DD
DD
BIAS
1µF, C
= 1µF, C1 = C2 = 1µF, PREF = unconnected, GAIN1 = 1, GAIN2 = GAIN3 = VOL = 0V, measurement BW = 22Hz to
PVSS
22kHz, T = +25°C, unless otherwise noted.)
A
CROSSTALK vs. FREQUENCY
TURN-ON RESPONSE (SPEAKER MODE)
(SPEAKER MODE)
TURN-OFF RESPONSE (SPEAKER MODE)
MAX9756 toc11
MAX9756 toc12
0
V
= 200mV
P-P
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
IN
SHDN
5V/div
SHDN
5V/div
OUT_+
2V/div
RIGHT TO LEFT
OUT_+
2V/div
OUT_-
2V/div
LEFT TO RIGHT
OUT_-
2V/div
OUT_+ - OUT_-
50mV/div
OUT_+ - OUT_-
50mV/div
10
100
1k
FREQUENCY (Hz)
10k
100k
10ms/div
10ms/div
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (HEADPHONE MODE)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (HEADPHONE MODE)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (HEADPHONE MODE)
10
10
10
V
= 5V
V
= 3.3V
DD
V
= 5V
DD
DD
R = 32Ω
L
R = 16Ω
L
R = 16Ω
L
1
1
1
OUTPUT POWER = 100mW
OUTPUT POWER = 80mW
OUTPUT POWER = 20mW
0.1
0.1
0.1
0.01
0.001
0.01
0.001
0.01
0.001
OUTPUT POWER = 40mW
OUTPUT POWER = 20mW
OUTPUT POWER = 60mW
10
100
1k
10k
100k
10
100
1k
10k
100k
10
100
1k
10k
100k
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (HEADPHONE MODE)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (HEADPHONE MODE)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (HEADPHONE MODE)
10
100
100
HPV = 5V
DD
R = 16Ω
L
HPV = 5V
DD
R = 32Ω
L
V
= 3.3V
DD
R = 32Ω
L
10
1
10
1
1
f
= 10kHz
IN
f
= 1kHz
IN
f
= 1kHz
f
= 100Hz
IN
IN
0.1
OUTPUT POWER = 50mW
0.1
0.1
0.01
0.001
0.01
0.001
0.01
0.001
OUTPUT POWER = 20mW
f
= 10kHz
f
= 100Hz
IN
IN
0
20 40 60 80 100 120 140 160 180 200
OUTPUT POWER (mW)
0
10 20 30 40 50 60 70 80 90 100
OUTPUT POWER (mW)
10
100
1k
10k
100k
FREQUENCY (Hz)
_______________________________________________________________________________________
7
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
Typical Operating Characteristics (continued)
(V
= PV
= HPV
= CPV
= IN = +5.0V, GND = PGND = CPGND = 0V, SHDN = V , REGEN = DR = SET = GND, C
=
DD
DD
DD
DD
DD
BIAS
1µF, C
= 1µF, C1 = C2 = 1µF, PREF = unconnected, GAIN1 = 1, GAIN2 = GAIN3 = VOL = 0V, measurement BW = 22Hz to
PVSS
22kHz, T = +25°C, unless otherwise noted.)
A
OUTPUT POWER vs. LOAD RESISTANCE
(HEADPHONE MODE)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (HEADPHONE MODE)
100
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (HEADPHONE MODE)
140
120
100
80
100
HPV = 3.3V
HPV = 3.3V
DD
DD
HPV = 3.3V
DD
f = 1kHz
R = 16Ω
R = 32Ω
L
L
10
1
10
1
THD+N = 10%
f
= 1kHz
IN
f
= 1kHz
IN
f = 100Hz
IN
f
= 100Hz
IN
THD+N = 1%
60
0.1
0.1
40
f
= 10kHz
100
0.01
0.001
IN
0.01
0.001
20
f
= 10kHz
IN
0
10
100
LOAD RESISTANCE (Ω)
1000
20 30
0
20
40
60
80
120
0
10
40 50 60 70 80 90 100
OUTPUT POWER (mW)
OUTPUT POWER (mW)
POWER DISSIPATION vs. OUTPUT POWER
(HEADPHONE MODE)
OUTPUT POWER vs. SUPPLY VOLTAGE
(HEADPHONE MODE)
OUTPUT POWER vs. LOAD RESISTANCE
(HEADPHONE MODE)
0.8
0.6
0.4
0.2
0
200
180
160
140
120
100
80
140
130
120
110
100
90
80
70
60
50
HPV = 5V
DD
f = 1kHz
THD+N = 1%
f = 1kHz
P
= P + P
HL HR
OUT
R = 16Ω
L
R = 16Ω
L
THD+N = 10%
THD+N = 1%
R = 32Ω
L
60
40
30
20
10
R = 32Ω
L
40
20
0
0
0
25 50 75 100 125 150 175 200 225 250
OUTPUT POWER (mW)
10
100
1000
3.0
3.5
4.0
4.5
5.0
5.5
LOAD RESISTANCE (Ω)
SUPPLY VOLTAGE (V)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY (HEADPHONE MODE)
OUTPUT POWER vs. CHARGE-PUMP
CAPACITANCE (HEADPHONE MODE)
CROSSTALK vs. FREQUENCY
(HEADPHONE MODE)
150
140
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
f = 1kHz
THD+N = 1%
V
= 100mV
P-P
RIPPLE
R = 32Ω
f = 1kHz
L
INPUTS AC-GROUNDED
130
120
110
V
= 200mV
C1 = C2 = 1µF
IN
P-P
100
90
HPV = 3.3V
DD
RIGHT TO LEFT
80
70
C1 = C2 = 2.2µF
60
50
LEFT TO RIGHT
40
30
20
HPV = 5V
DD
20
35 40
25 30
LOAD (Ω)
10 15
45 50
10
100
1k
10k
100k
0.01
0.1
1
10
100
FREQUENCY (Hz)
FREQUENCY (Hz)
8
_______________________________________________________________________________________
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
Typical Operating Characteristics (continued)
(V
= PV
= HPV
= CPV
= IN = +5.0V, GND = PGND = CPGND = 0V, SHDN = V , REGEN = DR = SET = GND, C
=
DD
DD
DD
DD
DD
BIAS
1µF, C
= 1µF, C1 = C2 = 1µF, PREF = unconnected, GAIN1 = 1, GAIN2 = GAIN3 = VOL = 0V, measurement BW = 22Hz to
PVSS
22kHz, T = +25°C, unless otherwise noted.)
A
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
TURN-OFF RESPONSE (HEADPHONE MODE)
TURN-ON RESPONSE (HEADPHONE MODE)
MAX9756 toc29
MAX9756 toc28
20
17
14
11
8
SHDN
5V/div
SHDN
5V/div
HPS = GND
HPR
10mV/div
HPR
10mV/div
HPS = V
DD
HPL
10mV/div
HPL
10mV/div
5
4.5
4.7
4.9
5.1
5.3
5.5
10ms/div
10ms/div
SUPPLY VOLTAGE (V)
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE
POWER LIMITING OF SINE BURST
POWER LIMITING OF SINE BURST
(FAST ATTACK AND SLOW RELEASE)
(FAST ATTACK AND FAST RELEASE)
MAX9756 toc32
MAX9756 toc33
600
500
400
300
200
100
0
OUTPUT
2V/div
OUTPUT
2V/div
CT
1V/div
CT
1V/div
4.5
4.7
4.9
5.1
5.3
5.5
10ms/div
40ms/div
SUPPLY VOLTAGE (V)
LDO OUTPUT VOLTAGE ACCURACY
vs. LOAD CURRENT
POWER LIMITING OF SINE BURST
(SLOW ATTACK AND SLOW RELEASE)
MAX9756 toc33
2.0
1.5
1.0
0.5
0
OUTPUT
2V/div
-0.5
-1.0
-1.5
-2.0
CT
1V/div
0
25
50
75
100
125
150
2s/div
LOAD CURRENT (mA)
_______________________________________________________________________________________
9
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
Typical Operating Characteristics (continued)
(V
= PV
= HPV
= CPV
= IN = +5.0V, GND = PGND = CPGND = 0V, SHDN = V , REGEN = DR = SET = GND, C
=
DD
DD
DD
DD
DD
BIAS
1µF, C
= 1µF, C1 = C2 = 1µF, PREF = unconnected, GAIN1 = 1, GAIN2 = GAIN3 = VOL = 0V, measurement BW = 22Hz to
PVSS
22kHz, T = +25°C, unless otherwise noted.)
A
CROSSTALK vs. FREQUENCY
LDO OUTPUT VOLTAGE ACCURACY
vs. TEMPERATURE
DROPOUT VOLTAGE
vs. LOAD CURRENT
(LDO)
5
4
0
300
200
100
0
R
P
= 4Ω
OUT(SPK)
L
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
= 1W
3
2
1
0
-1
-2
-3
-4
-5
-100
-200
-300
I
= 90mA
OUT
I
= 50mA
OUT
I
= 10mA
OUT
0.1
-40
-15
10
35
60
85
0.01
1
10
100
0
25
50
75
100
125
150
TEMPERATURE (°C)
FREQUENCY (Hz)
LOAD CURRENT (mA)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY (LDO)
LDO OUTPUT NOISE
MAX9756 toc40
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
V
= 100mV
P-P
RIPPLE
LDO_OUT
1mV/div
-100
10
100
1k
FREQUENCY (Hz)
10k
100k
200µs/div
10 ______________________________________________________________________________________
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
Typical Operating Characteristics (continued)
(V
= PV
= HPV
= CPV
= IN = +5.0V, GND = PGND = CPGND = 0V, SHDN = V , REGEN = DR = SET = GND, C
=
DD
DD
DD
DD
DD
BIAS
1µF, C
= 1µF, C1 = C2 = 1µF, PREF = unconnected, GAIN1 = 1, GAIN2 = GAIN3 = VOL = 0V, measurement BW = 22Hz to
PVSS
22kHz, T = +25°C, unless otherwise noted.)
A
OUTPUT NOISE
vs. FREQUENCY (LDO)
110
LINE-TRANSIENT RESPONSE
MAX9756 toc42
C
= 2µF
OUT
100
90
80
70
60
50
40
30
20
10
5.5V
10Hz TO 100kHz
V
IN
500mV/div
4.5V
LDO_OUT
20mV/div
10
100
1k
FREQUENCY (Hz)
10k
100k
40µs/div
LOAD-TRANSIENT RESPONSE
LDO SHUTDOWN RESPONSE
MAX9756 toc43
MAX9756 toc44
50V
REGEN
5V/div
I
LOAD
25mV/div
0V
LDO_OUT = 4.65V
20mV/div
LDO_OUT
1V/div
20µs/div
100ms/div
Pin Description
PIN
NAME
FUNCTION
MAX9756 MAX9757 MAX9758
1
32
32
INL
Left-Channel Audio Input
2
3
1
2
1
GAIN1 Gain Control Input 1
GAIN2 Gain Control Input 2
GAIN3 Gain Control Input 3
BEEP Audible Alert Beep Input
PGND Power Ground
2
3
4
3
5
4
4
6, 22
7
5, 21
6
5, 21
6
OUTL+ Left-Channel Positive Speaker Output
OUTL- Left-Channel Negative Speaker Output
8
7
7
9,19
8,18
8, 18
PV
Speaker Amplifier Power Supply. Bypass with 1µF ceramic capacitor to PGND.
DD
______________________________________________________________________________________ 11
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
Pin Description (continued)
PIN
NAME
CPV
FUNCTION
MAX9756 MAX9757 MAX9758
10
9
9
Charge-Pump Power Supply. Bypass with 1µF ceramic capacitor to CPGND.
DD
Charge-Pump Flying-Capacitor Positive Terminal. Connect a 1µF capacitor from C1P
to C1N.
11
10
10
C1P
12
13
14
11
12
13
11
12
13
CPGND Charge-Pump Ground
Charge-Pump Flying-Capacitor Negative Terminal. Connect a 1µF capacitor from
C1N
CPV
C1P to C1N.
Charge-Pump Negative Output. Connect to V
.
SS
SS
Headphone Amplifier Negative Power Supply. Bypass with 1µF ceramic capacitor to
GND.
15
14
14
V
SS
16
17
15
16
15
16
HPR
HPL
Right Headphone Output
Left Headphone Output
18
17
17
HPV
Headphone Positive Power Supply. Bypass with 1µF ceramic capacitor to GND.
DD
20
21
19
20
19
20
OUTR- Right-Channel Negative Speaker Output
OUTR+ Right-Channel Positive Speaker Output
Headphone Sense Input. Leave HPS unconnected if automatic headphone sensing
is not used.
23
24
22
—
22
23
HPS
LDO Enable. Connect REGEN to V to enable the LDO. Connect to GND to
DD
disable LDO.
REGEN
Automatic Level Control Attack to Release Time Ratio Select. Hardwired to V
GND, or BIAS to set the attack to release ratio; see the ALC section.
,
DD
25
26
27
28
29
23
24
25
26
27
—
24
25
26
—
DR
BIAS
SHDN
VOL
Common-Mode Bias Voltage. Bypass with a 1.0µF capacitor to GND.
Shutdown Input. Drive SHDN low to disable the audio amplifiers. Connect SHDN to
for normal operation.
V
DD
Analog Volume Control Input
Power-Limiting Input. Connect a resistor from PREF to GND to set the speaker output
clamping level. Leave PREF unconnected to disable ALC; see the ALC section.
PREF
Regulator Feedback Input. Connect to GND for 4.65V fixed output. Connect to
resistor-divider for adjustable output; see the Low-Dropout Linear Regulator section.
30
—
27
SET
31
32
33
34
28
29
—
—
28
—
—
30
GND
Ground
V
Power Supply
DD
IN
LDO Input. Bypass with two 1µF ceramic capacitors to GND.
LDO Output. Bypass with two 1µF ceramic capacitors to GND.
OUT
Automatic Level Control Attack and Release Timing Capacitor. Connect CT to GND
to disable ALC; see the ALC section.
35
30
—
CT
36
—
31
—
31
29
INR
Right-Channel Audio Input
V
Power-Supply and LDO Input. Bypass with two 1µF ceramic capacitors to GND.
DD
Exposed Pad. The external pad lowers the package’s thermal impedance by
providing a direct-heat conduction path from the die to the PC board. Connect the
exposed thermal pad to GND.
EP
EP
EP
EP
12 ______________________________________________________________________________________
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
All devices feature a single-supply voltage, a shut-
Detailed Description
down mode, logic-selectable gain, and a headphone
The MAX9756/MAX9757/MAX9758 combine dual, 2W
sense input. Industry-leading click-and-pop suppres-
BTL stereo audio power amplifiers with a DirectDrive
sion eliminates audible transients during power and
headphone amplifier in a single device. The stereo
shutdown cycles.
power amplifiers deliver up to 2.3W per channel into a
Each signal path consists of an input amplifier that sets
the signal-path gain and feeds both the speaker and
headphone amplifiers (Figure 1). The speaker amplifier
uses a BTL architecture, doubling the voltage drive to
the speakers and eliminating the need for DC-blocking
capacitors. The output consists of two signals, identical
in magnitude, but 180° out of phase.
3Ω speaker from a 5V supply and the stereo head-
phone amplifiers deliver up to 130mW per channel into
a 16Ω headphone from a 5V supply.
The MAX9756/MAX9757 feature ALC that automatically
controls output power to the speaker, preventing loud-
speaker, overload and provides optimized dynamic
range.
The headphone amplifiers use Maxim’s DirectDrive
architecture that eliminates the bulky output DC-blocking
capacitors required by traditional headphone amplifiers.
The MAX9756/MAX9757/MAX9758 feature 31-step ana-
log volume control and a BEEP input. The amplifier
gain is pin programmable. These devices feature click-
and-pop suppression, eliminating the need for discrete
muting circuitry. Speaker and headphone outputs have
short-circuit and thermal protection.
A charge pump inverts the positive supply (CPV ), cre-
DD
ating a negative supply (CPV ). The headphone ampli-
SS
fiers operate from these bipolar supplies with their
outputs biased about GND (Figure 2).
The MAX9756/MAX9758s’ internal LDO features
Maxim’s Dual Mode™ feedback. The LDO output volt-
age is either fixed at 4.65V (SET = GND), or adjusted
between 1.23V and 5V using a resistive divider at SET.
The LDO delivers up to 150mA of continuous current,
and can be enabled independently from the audio
amplifiers. Short-circuit and thermal-overload protec-
tion are provided for the LDO.
The amplifiers have almost twice the supply range
compared to other single-supply amplifiers, nearly qua-
drupling the available output power. The benefit of the
GND bias is that the amplifier outputs do not have a DC
component (typically V /2). This eliminates the large
DD
DC-blocking capacitors required with conventional
headphone amplifiers, conserving board space and
system cost while improving frequency response.
IN_
V
DD
V
OUT
V
DD
/2
ALC
OUT_+
GND
BIAS
BIAS
CONVENTIONAL DRIVER-BIASING SCHEME
+V
DD
VOLUME
VOL
OUT_-
HP_
CONTROL
BIAS
GND
GND
-V
DD
DirectDrive BIASING SCHEME
Figure 1. MAX9756/MAX9757 Signal Path
Figure 2. Traditional Headphone Amplifier Output Waveform
vs. DirectDrive Headphone Amplifier Output Waveform
Dual Mode is a trademark of Maxim Integrated Products, Inc.
______________________________________________________________________________________ 13
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
The MAX9756/MAX9757/MAX9758 feature an under-
voltage lockout that prevents operation from an insuffi-
cient power supply and click-and-pop suppression that
eliminates audible transients on startup and shutdown.
The amplifiers include thermal-overload and short-cir-
cuit protection. An additional feature of the amplifiers is
that there is no phase inversion from input to output.
applied to the input, eliminating output clipping. Figure 3
shows a comparison of an overgained speaker input with
and without ALC.
The MAX9756/MAX9758 control the gain to the speakers
by first detecting that the output voltage to the speaker
has exceeded a preset limit. The speaker amplifier gain
is rapidly reduced to correct for the excessive output
power. This process is known as the attack time. When
the signal subsequently lowers in amplitude, the gain is
held at the reduced state for a short period before slowly
increasing to the normal value. This process is known as
the hold and release time. The speed at which the ampli-
fiers adjust to changing input signals is set by the exter-
Automatic Level Control (ALC)
Two-watt amplifiers are commonly used in notebook
PCs (almost always powered from a 5V supply). With
an 8Ω speaker driven from a BTL amplifier, the maxi-
m
u
m
theoretical continuous power available is:
nal timing capacitor C and the setting of logic input
CT
DR. The output power limit can be set by adjusting the
value of the external resistor connected to PREF. Gain
reduction is a function of input signal amplitude with a
maximum ALC attenuation of 6dB. Figure 4 shows the
effect of an input burst exceeding the preset limit, output
attack, hold and release times.
2
2
⎛
⎞
⎛
⎞
⎛
⎞
⎛
⎞
V
5
PEAK
⎜
⎜
⎜
⎜
⎜
⎝
⎟
⎟
⎟
⎟
⎟
⎠
⎜
⎜
⎜
⎜
⎜
⎝
⎟
⎟
⎟
⎟
⎟
⎠
⎜
⎟
⎜
⎟
⎝
R
⎠
⎝
⎠
2
2
8
P
=
=
= 1.56W
OUT
SPEAKER
This process (referred to as “limiting” in audio) limits the
amplifier output power so loudspeaker overload can be
prevented. If the attack and release times are configured
to respond too fast, audible artifacts often, described as
“pumping” or “breathing,” can occur as the gain is rapid-
ly adjusted to follow the dynamics of the signal. For best
results, adjust the time constant of the ALC to accommo-
date the source material. Notebook applications in which
music CDs and DVDs are the main audio source, a
495µs attack time with a 990ms release time is recom-
mended with a 1.2W output into an 8Ω load.
See Figure 5 for suggested ALC component values.
The ALC feature offers two benefits:
1) To limit amplifier power to protect a loudspeaker.
2) To make input signals with a wide dynamic range
more intelligible by boosting low-level signals with-
out distorting the high-level signals.
A device without ALC experiences clipping at the output
when too much gain is applied to the input. ALC pre-
vents clipping at the output when too much gain is
ALC ENABLE, NO CLIPPING AT THE OUTPUT
ALC DISABLE, CLIPPING AT THE OUTPUT
INPUT
SIGNAL
OUTPUT
SIGNAL
10ms/div
10ms/div
Figure 3. ALC Disabled vs. ALC Enabled
14 ______________________________________________________________________________________
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
This allows the louder passages to be reduced in vol-
ume, thereby maximizing output dynamic range.
Having the attack time too long can possibly result in
some damage to the loudspeaker under harsh condi-
tions.
OUTPUT
2V/div
Hold Time
Hold time is the delay after the signal falls below the
threshold level before the release phase is initiated.
Hold time is internally set to 50ms and nonadjustable.
The hold time is cancelled by any signal exceeding the
set threshold level and attack is reinitiated.
CT
1V/div
Release Time
The release time is how long it takes for the gain to
return to its normal level after the input signal has fallen
10ms/div
below the threshold level and 50ms hold time has
expired. Release time is defined as release from a 6dB
gain compression to 10% of the nominal gain setting
after the input signal has fallen below PREF threshold
and the 50ms hold time has expired. Release time is
adjustable between 95ms and 10s. The release time is
Figure 4. Attack, Hold, and Release Time
Attack Time
The attack time is the time it takes to reduce the gain
after the input signal has exceeded the threshold level.
Suggested attack time range is from 150µs to 50ms.
The gain attenuation in attack is exponential and the
attack time is defined as one time constant. The time
set by picking an attack time using C and setting the
CT
attack to release time ratio by configuring DR as shown
in Table 2. Release time is linear in dB with time and is
inversely proportional to the magnitude of gain com-
pression:
constant of the attack is given by 15,000 x C
sec-
CT
• Use a small ratio to maximize the speed of the ALC.
onds (where C is the external timing capacitor).
CT
• Use a large ratio to maximize the sound quality and
prevent repeated excursions above the threshold
from being independently adjusted by the ALC.
• Use a short attack time for the ALC to react quickly
to transient signals, such as snare drum beats
(music) or gun shots (DVD). Fast attack times can
lead to gain “pumping” where rapid ALC action can
be heard reacting to dynamic material.
Release and attack times are set by selecting the
capacitance value between CT and GND, and by set-
ting the logic state of DR (Table 1). DR is a tristate logic
input that sets the attack-to-release time ratio. A fixed
hold time of 50ms is internally added to the release time.
• Use a longer attack time to allow the ALC to ignore
short-duration peaks and only reduce the gain when
a noticeable increase in loudness occurs. Short-dura-
tion peaks are not reduced, but louder passages are.
Table 1. Attack and Release Time
ATTACK TIME
DR = ‘X’
150µs
RELEASE TIME
TIMING CAPACITOR
(C
)
CT
DR = V
DR = V
DR = GND
300ms
990ms
3s
DD
BIAS
10nF
33nF
100nF
330nF
1µF
30ms
99ms
300ms
990ms
3s
95ms
495µs
313ms
950ms
3.1s
9.5s
—
1.5ms
4.95ms
15ms
9.9s
—
2.2µF
3.3µF
33ms
6.6s
—
49.5ms
10s
—
—
______________________________________________________________________________________ 15
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
The release/attack time ratio that can be achieved by
programming DR is listed in Table 2.
OUTPUT POWER THRESHOLD
vs. R
PREF
3.0
2.5
2.0
1.5
1.0
0.5
0
Table 2. Release to Attack Ratio
DR
RELEASE/ATTACK RATIO
R = 4Ω
L
V
200
633
DD
V
BIAS
GND
2000
R = 8Ω
L
5V
V
DD
DR
CT
100 110 120 130 140 150 160 170 180 190 200
(kΩ)
R
PREF
MAX9756
MAX9757
33nF
Figure 6. Output Power Threshold vs. R
PREF
PREF
limit on an 8Ω load and a 200kΩ resistor results in a
1.5W clamp limit on an 8Ω load (Figure 6).
180kΩ
Use the following equation to choose the value for
R
for the desired maximum output power level
PREF
based on a sine wave input:
VALUES SHOWN FOR AN OUTPUT POWER THRESHOLD OF 1.2W WITH AN
R = 8Ω ATTACK TIME OF 495µs AND A RELEASE TIME OF 990ms
L
⎛
⎜
⎜
⎝
⎞
⎟
⎟
⎠
⎛
⎞
⎛
⎞
P
R
L
8
OUT
R
= 180kΩ
×
⎜
⎟
⎜
⎟
PREF
Figure 5. Recommended Output Power Threshold, Attack, and
Release Time Components
1.166
⎝
⎠
⎝
⎠
Output Power Threshold
To set the threshold at which speaker output is
clamped, an external resistor must be connected from
PREF to ground. The suggested external resistor range
is from 100kΩ to 200kΩ (for best results use a 1% resis-
tor). Leaving PREF unconnected disables the ALC
function. A constant current of 12µA is sourced at
PREF, so that a 180kΩ resistor results in 1.2W clamp
Gain Selection
The MAX9756/MAX9757/MAX9758 feature an internally
set, selectable gain. The GAIN1, GAIN2, and GAIN3
inputs set the maximum gain for the speaker and head-
phone amplifiers (Table 3). The gain of the device can
vary based upon the voltage at VOL but does not
exceed the maximum gain listed below (see the Analog
Volume (VOL) Control section).
Table 3. Maximum Gain Settings
GAIN3
GAIN2
GAIN1
SPEAKER MODE GAIN (dB)
HEADPHONE MODE GAIN (dB)
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
+15
+16.5
+18
0
0
+3
+3
0
+19.5
+21
+22.5
+24
0
+3
+3
+25.5
16 ______________________________________________________________________________________
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
Analog Volume Control (VOL)
The MAX9756/MAX9757/MAX9758 feature an analog
volume control that varies the gain of the device in 31
MAX9756
DD
HPV
VOL
discrete steps based upon the DC voltage applied to
VOL (see Table 4). The input range of VOL is from 0
V
REF
(full volume) to HPV
(full mute), with example step
DD
DAC
sizes shown in Table 3. Connect the reference of the
device driving VOL (Figure 7) to HPV . Connect VOL
DD
to GND (full volume) if volume control is not used.
Figure 7. Volume Control Circuit
Table 4. Volume Levels
V
(V) = MULTIPLIER x
SPEAKER MODE
GAIN (dB)
HEADPHONE MODE
GAIN (dB)
VOL
HPV
DD
GAIN3 = 0 GAIN3 = 0 GAIN3 = 0 GAIN3 = 0 GAIN3 = 1 GAIN3 = 1 GAIN3 = 1 GAIN3 = 1 GAIN3 = X GAIN3 = X
GAIN2 = 0 GAIN2 = 0 GAIN2 = 1 GAIN2 = 1 GAIN2 = 0 GAIN2 = 0 GAIN2 = 1 GAIN2 = 1 GAIN2 = 0 GAIN2 = 1
GAIN1 = 0 GAIN1 = 1 GAIN1 = 0 GAIN1 = 1 GAIN1 = 0 GAIN1 = 1 GAIN1 = 0 GAIN1 = 1 GAIN1 = X GAIN1 = X
V
V
VOL
VOL
MULTIPLIER
*
*
(MAX)
(MIN)
0.07
0.16
0.18
0.21
0.23
0.25
0.28
0.30
0.32
0.35
0.37
0.39
0.42
0.44
0.46
0.49
0.51
0.54
0.56
0.58
0.61
0.63
0.65
0.68
0.70
0.72
0.75
0.77
0.79
0.82
0.84
0.93
0.00
0.49
0.57
0.64
0.72
0.80
0.88
0.95
1.03
1.11
1.19
1.26
1.34
1.42
1.50
1.57
1.65
1.73
1.80
1.88
1.96
2.04
2.11
2.19
2.27
2.35
2.42
2.50
2.58
2.66
2.73
2.81
0.49
0.57
0.64
0.72
0.80
0.88
0.95
1.03
1.11
1.19
1.26
1.34
1.42
1.50
1.57
1.65
1.73
1.80
1.88
1.96
2.04
2.11
2.19
2.27
2.35
2.42
2.50
2.58
2.66
2.73
2.81
3.30
15
14
16.5
16
18
17.5
17
19.5
19
21
20
19
18
16
14
12
10
8
22.5
22
21
20
19
18
16
14
12
10
8
24
23.5
23
22.5
22
21
20
19
18
16
14
12
10
8
25.5
25
0
-1
3
2.5
2
13
15
18.5
18
24.5
24
-2
12
14
16.5
16
-3
1.5
1
10
13
17.5
17
23.5
23
-5
8
12
15
-7
0
6
10
14
16.5
16
22.5
22
-9
-1
4
8
13
-11
-13
-15
-17
-19
-21
-23
-25
-27
-29
-31
-33
-35
-37
-39
-41
-43
-47
-51
-55
-59
-63
-67
-71
MUTE
-2
2
6
12
15
21
-3
0
4
10
14
6
20
-5
-2
2
8
13
4
19
-7
-4
0
6
12
2
6
18
-9
-6
-2
4
10
0
4
16
-11
-13
-15
-17
-19
-21
-23
-25
-27
-29
-31
-33
-35
-37
-39
-41
-43
-47
-51
MUTE
-8
-4
2
8
-2
2
14
-10
-12
-14
-16
-18
-20
-22
-24
-26
-28
-32
-36
-40
-44
-48
-52
-56
MUTE
-6
0
6
-4
0
6
12
-8
-2
4
-6
-2
4
10
-10
-12
-14
-16
-18
-20
-22
-24
-26
-28
-32
-36
-40
-44
-48
MUTE
-4
2
-8
-4
2
8
-6
0
-10
-12
-14
-16
-18
-20
-22
-26
-30
-34
-38
-42
-46
-50
MUTE
-6
0
6
-8
-2
-8
-2
4
-10
-12
-14
-16
-18
-20
-22
-24
-26
-28
-32
-36
MUTE
-4
-10
-12
-14
-16
-18
-20
-22
-26
-30
-34
-38
-42
MUTE
-4
2
-6
-6
0
-8
-8
-2
-10
-12
-14
-16
-18
-20
-22
-24
-26
MUTE
-10
-12
-14
-16
-18
-20
-22
-26
-30
MUTE
-4
-6
-8
-10
-12
-14
-15
-18
-20
MUTE
*Based on HPV
X = Don’t care.
= 3.3V.
DD
______________________________________________________________________________________ 17
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
Since the volume control (VOL) ADC is ratiometric to
HPV , any variations in HPV
are negated. The gain
DD
DD
VOLUME CONTROL TRANSFER FUNCTION
step sizes are not constant; the step sizes are
0.5dB/step at the upper extreme, 2dB/step in the
midrange, and 4dB/step at the lower extreme. Figure 8
shows the transfer function of the volume control for a
3.3V supply.
40
20
GAIN1 = GAIN2 = GAIN3 = 1
HPV = 3.3V
DD
SPEAKER MODE
0
Low-Dropout Linear Regulator
The MAX9756/MAX9758s’ low-dropout linear regulator
(LDO) can be used to provide a clean power supply to
a CODEC or other circuitry. The LDO can be enabled
independently of the audio amplifiers. REGEN
-20
-40
-60
-80
HEADPHONE MODE
enables/disables the LDO, set REGEN = V
to enable
DD
the LDO or set REGEN = GND to disable. The LDO is
capable of providing up to 150mA continuous current
and features Maxim’s Dual Mode feedback. When SET
is connected to GND, the output is internally set to
approximately 4.65V. Adjust the output from 1.23V to
5V by connecting two external resistors, used as a volt-
age-divider, at SET (Figure 9).
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
(V)
V
VOL
Figure 8. Volume Control Transfer Function
The output voltage is set by the following equation:
OUT
R1
R2
⎛
⎞
V
= V
1+
⎜
⎝
⎟
⎠
OUT
SET
R1
R2
10pF
1µF
1µF
MAX9756
MAX9758
where V
= 1.23V.
SET
SET
To simplify resistor selection:
⎛
⎞
V
V
OUT
GND
R1= R2
−1
⎜
⎟
⎝
⎠
SET
Since the input bias current at SET is nominally zero,
large resistance values can be used for R1 and R2 to
minimize power consumption without losing accuracy.
Up to 1.5MΩ is acceptable for R2.
To minimize the current consumption, it is desirable to
use high-value resistors (> 10kΩ for the external feed-
back divider (R1, R2). The input capacitance at SET
and the stray and wiring capacitance should be com-
pensated by placing a small capacitor (in the 10pF
range) across the upper feedback resistor R1 (see
Figure 9).
Figure 9. Adjustable Output Using External Feedback Resistors
The ESR of each capacitor should not exceed 40mΩ
for good stability up to the full-rated current (150mA).
Place the capacitors as close as possible to the device
to limit the parasitic resistance and inductance. There
is no upper limit to the amount of additional bypass
capacitance.
DirectDrive Headphone Amplifier
Unlike the MAX9756/MAX9757/MAX9758, conventional
single-supply headphone amplifiers typically have their
outputs biased at half the supply voltage for maximum
dynamic range. Large coupling capacitors are needed
to block this DC bias from the headphones. Without
these capacitors, a significant amount of DC current
flows to the headphone, resulting in unnecessary
power dissipation and possible damage to both head-
phone and headphone amplifier.
This capacitor creates a zero in the feedback loop to
reduce overshoot. Overcompensation can cause poor
stability in the high current range.
The regulator should be compensated with two 1µF
ceramic capacitors connected between IN and GND
and OUT and GND. X7R dielectric with 10% tolerance
is recommended.
18 ______________________________________________________________________________________
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
Maxim’s DirectDrive architecture uses a charge pump to
create an internal negative supply voltage. This allows the
MAX9756/MAX9757/MAX9758 headphone amplifier out-
put to be biased at GND, almost doubling the dynamic
range while operating from a single supply. With no DC
component, there is no need for the large DC-blocking
capacitors. Instead of two large capacitors (220µF, typ),
the MAX9756/MAX9757/MAX9758 charge pump requires
only two small ceramic capacitors (1µF typ), conserving
board space, reducing cost, and improving the frequen-
cy response of the headphone amplifier. See the Output
Power vs. Charge-Pump Capacitance graph in the
Typical Operating Characteristics for details of the possi-
ble capacitor values.
Larger values of C
physically larger, more expensive capacitors. Figure 10
shows the relationship between the size of C and
the resulting low-frequency attenuation. Note that the
-3dB point for a 16Ω headphone with a 100µF-blocking
capacitor is 100Hz, well within the audio band.
reduce the attenuation but are
OUT
OUT
Charge Pump
The MAX9756/MAX9757/MAX9758 feature a low-noise
inverting charge pump to generate the negative rail
necessary for DirectDrive headphone operation. The
switching frequency is well beyond the audio range,
and does not interfere with the audio signals. The
switch drivers feature a controlled switching speed that
minimizes noise generated by turn-on and turn-off tran-
sients. Limiting the switching speed of the charge
pump minimizes the di/dt noise caused by the parasitic
bond wire and trace inductance.
Low-Frequency Response
In addition to the cost and size disadvantages, the DC-
blocking capacitors limit the low-frequency response of
the amplifier. The impedance of the headphone load to
the DC-blocking capacitor forms a highpass filter with
the -3dB point determined by:
Headphone Sense Input (HPS)
The headphone sense input (HPS) monitors the head-
phone jack and automatically configures the MAX9756/
MAX9757/MAX9758 based upon the voltage applied at
HPS. A voltage of less than 0.8V enables the speaker
amplifier. A voltage of greater than 2V disables the
speaker amplifiers and enables the headphone ampli-
fiers. For automatic headphone detection, connect HPS
to the control pin of a 3-wire headphone jack as shown
in Figure 11. With no headphone present, the output
impedance of the headphone amplifier pulls HPS low.
When a headphone plug is inserted into the jack, the
control pin is disconnected from the tip contact and
1
f − 3dB =
2πR C
L
OUT
where R is the impedance of the headphone and
L
C
OUT
is the value of the DC-blocking capacitor.
The highpass filter is required by conventional single-
ended, single-supply headphone amplifiers to block the
midrail DC component of the audio signal from the
headphones. Depending on the -3dB point, the filter can
attenuate low-frequency signals within the audio band.
HPS is pulled to V
with 35µA.
DD
LOW-FREQUENCY ROLLOFF
V
(R = 16Ω)
L
DD
MAX9756/
0
MAX9757/
MAX9758
-1.5
35μA
DirectDrive
330μF
220μF
100μF
-3.0
-4.5
-6.0
SHUTDOWN
CONTROL
HPS
HPL
-7.5
-9.0
HPR
33μF
-10.5
-12.0
14kΩ
14kΩ
-13.5
-15.0
10
100
1k
FREQUENCY (Hz)
10k
100k
Figure 10. Low-Frequency Attenuation of Common DC-
Blocking Capacitor Values
Figure 11. HPS Configuration
______________________________________________________________________________________ 19
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
BIAS
⎛
⎞
V
The MAX9756/MAX9757/MAX9758 feature an internally
generated, power-supply independent, common-mode
bias voltage of 2.5V referenced to GND. BIAS provides
both click-and-pop suppression and sets the DC bias
level for the amplifiers. Choose the value of the bypass
capacitor as described in the BIAS Capacitor section.
No external load should be applied to BIAS. Any load
lowers the BIAS voltage, affecting the overall perfor-
mance of the device.
47kΩ
OUT(BEEP)
=
+ A
V(BEEPOUT)
⎜
⎟
V
R
B
⎝
⎠
IN(BEEP)
where 47kΩ is the value of the BEEP amplifier feedback
resistor, V
is the BEEP amplifier output, V
IN(BEEP)
BEEP
is the BEEP input amplitude, and V
is the total
OUT(BEEP)
) is given by the values
BEEP output signal. A
V(BEEPOUT
listed in Table 5. Note that V
must be higher than
BEEP
300mV . The BEEP amplifier can be set up as either
P-P
an attenuator, if the original alert signal amplitude is too
large, or to gain up the alert signal if it is below
BEEP Input
The MAX9756/MAX9757/MAX9758 feature an audible
alert beep input (BEEP) that accepts a mono system
alert signal and mixes it into the stereo audio path.
300mV . AC-couple the alert signal to BEEP. Choose
P-P
the value of the coupling capacitor as described in the
Input Filtering section. Multiple beep inputs can be
summed (Figure 12).
When the amplitude of V
exceeds 300mV
and
BEEP
P-P
the frequency of the beep signal is greater than 300Hz,
the beep signal is mixed into the active audio path
(speaker or headphone). If the signal at V
is either
BEEP
Table 5. BEEP Output Gain
< 300mV
or < 300Hz, the BEEP signal is not mixed
P-P
into the audio path. The amplitude of the BEEP signal at
the device output is roughly the amplitude V
the gain of the selected signal path.
A
V(BEEPOUT)
times
BEEP
GAIN3 GAIN2 GAIN1
HEADPHONE *
(V/V)
SPEAKER*
(V/V)
The input resistor (R ) sets the gain of the BEEP input
B
1.5
1.5
8.4
9.4
10
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
amplifier, and thus the amplitude of V
based on:
. Choose R
BEEP
B
1.78
1.78
1.5
V
× 47kΩ
IN(BEEP)
10
R
≤
B
V
15.8
18.8
20
BEEP
1.5
The total BEEP gain is given by:
1.78
1.78
20
*All output gains are for V
= GND.
VOL
R
B
0.47µF
0.47µF
0.47µF
47kΩ
SOURCE 1
SOURCE 2
SOURCE 3
47kΩ
R
B
47kΩ
SPEAKER/HEADPHONE
AMPLIFIER INPUTS
BEEP
V
BEEP
R
B
47kΩ
WINDOW
DETECTOR
(0.3V THRESHOLD)
P-P
MAX9756/
MAX9757/
MAX9758
FREQUENCY
DETECTOR
(300Hz THRESHOLD)
BIAS
Figure 12. Beep Input
20 ______________________________________________________________________________________
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
Shutdown (SHDN)
The MAX9756/MAX9757/MAX9758 feature a 0.2µA,
low-power shutdown mode that reduces quiescent cur-
V
+1
OUT(P-P)
rent consumption and extends battery life. Driving
SHDN low disables the drive amplifiers, bias circuitry,
and charge pump, and drives BIAS and all outputs to
2 x V
OUT(P-P)
GND. Connect SHDN to V
for normal operation.
DD
Click-and-Pop Suppression
-1
V
OUT(P-P)
Speaker Amplifier
The MAX9756/MAX9757/MAX9758 speaker amplifiers
feature Maxim’s comprehensive, industry-leading click-
and-pop suppression. During startup, the click-and-
pop suppression circuitry eliminates any audible
transient sources internal to the device. When entering
shutdown, both amplifier outputs ramp to GND quickly
and simultaneously.
Figure 13. Bridge-Tied Load Configuration
package is given in the Absolute Maximum Ratings
under Continuous Power Dissipation, or can be calcu-
lated by the following equation:
Headphone Amplifier
In conventional single-supply headphone amplifiers, the
output-coupling capacitor is a major contributor of audi-
ble clicks and pops. Since the MAX9756/MAX9757/
MAX9758 do not require output-coupling capacitors, no
audible transient occurs.
T
J(MAX) − T
A
P
=
DISSPKG(MAX)
θ
JA
where T
is +150°C, T is the ambient temperature,
A
J(MAX)
and θ is the reciprocal of the derating factor in °C/W as
JA
specified in the Absolute Maximum Ratings section. For
Additionally, the MAX9756/MAX9757/MAX9758 feature
extensive click-and-pop suppression that eliminates any
audible transient sources internal to the device. The
Turn-On/Turn-Off waveforms in the Typical Operating
Characteristics show that there are minimal spectral
components in the audible range at the output upon
startup and shutdown.
example, θ
of the 32-pin thin QFN package is
JA
+40.2°C/W. For optimum power dissipation, the exposed
paddle of the package should be connected to the
ground plane (see the Layout and Grounding section).
Output Power (Speaker Amplifier)
The increase in power delivered by the BTL configura-
tion directly results in an increase in internal power dis-
sipation over the single-ended configuration. The
maximum power dissipation for a given V
given by the following equation:
Applications Information
and load is
DD
BTL Speaker Amplifiers
The MAX9756/MAX9757/MAX9758 feature speaker
amplifiers designed to drive a load differentially, a config-
uration referred to as bridge-tied load (BTL). The BTL
configuration (Figure 13) offers advantages over the sin-
gle-ended configuration, where one side of the load is
connected to ground. Driving the load differentially dou-
bles the output voltage compared to a single-ended
amplifier under similar conditions.
2
2V
DD
P
=
DISS(MAX)
2
π R
L
If the power dissipation for a given application exceeds
the maximum allowed for a given package, either reduce
V
, increase load impedance, decrease the ambient
DD
temperature, or add heatsinking to the device or setting
PREF to limit output power to a safe level. Large output,
supply, and ground PC board traces improve the maxi-
mum power dissipation in the package. Thermal-over-
load protection limits total power dissipation in these
devices. When the junction temperature exceeds
+160°C, the thermal-protection circuitry disables the
amplifier output stage. The amplifiers are enabled once
the junction temperature cools by 15°C. This results in a
pulsing output under continuous thermal-overload condi-
tions as the device heats and cools.
Since the differential outputs are biased at 2.5V, there is
no net DC voltage across the load. This eliminates the
need for DC-blocking capacitors required for single-
ended amplifiers. These capacitors can be large and
expensive, can consume board space, and can degrade
low-frequency performance.
Power Dissipation and Heat Sinking
Under normal operating conditions, the MAX9756/
MAX9757/MAX9758 can dissipate a significant amount
of power. The maximum power dissipation for each
______________________________________________________________________________________ 21
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
Output Power (Headphone Amplifier)
The headphone amplifiers have been specified for the
100
HPV = 5V
R = 16Ω
L
worst-case scenario—when both inputs are in phase.
DD
Under this condition, the drivers simultaneously draw
10
current from the charge pump, leading to a slight loss
in headroom of V . In typical stereo audio applica-
SS
tions, the left and right signals have differences in both
magnitude and phase, subsequently leading to an
increase in the maximum attainable output power.
Figure 14 shows the two extreme cases for in and out
of phase. In reality, the available power lies between
these extremes.
1
0.1
OUTPUTS IN PHASE
0.01
0.001
OUTPUTS 180° OUT OF PHASE
Power Supplies
The MAX9756/MAX9757/MAX9758 have different sup-
plies for each portion of the device, allowing for the opti-
mum combination of headroom and power dissipation
and noise immunity. The speaker amplifiers are pow-
40
80
180
100 120 140 160 200
0
20
60
OUTPUT POWER (mW)
Figure 14. Total Harmonic Distortion Plus Noise vs. Output
Power with Inputs In/Out of Phase (Headphone Mode)
ered from PV . PV
ranges from 4.5V to 5.5V. The
DD
DD
headphone amplifiers are powered from HPV
and
DD
V
. HPV
is the positive supply of the headphone
SS
DD
amplifiers and ranges from 3V to 5.5V. V is the nega-
SS
Setting f
too high affects the amplifier’s low-fre-
tive supply of the headphone amplifiers. Connect V to
SS
-3dB
quency response. Use capacitors with low-voltage
coefficient dielectrics, such as tantalum or aluminum
electrolytic. Capacitors with high-voltage coefficients,
such as ceramics, may result in increased distortion at
low frequencies.
CPV . The charge pump is powered by CPV
.
DD
SS
CPV
ranges from 3V to 5.5V and should be the same
DD
potential as HPV . The charge pump inverts the volt-
DD
age at CPV , and the resulting voltage appears at
DD
CPV . The remainder of the device is powered by V
.
SS
DD
BIAS Capacitor
Component Selection
BIAS is the output of the internally generated DC bias
Input Filtering
voltage. The BIAS bypass capacitor, C
, improves
BIAS
The input capacitor (C ), in conjunction with the ampli-
IN
IN
PSRR and THD+N by reducing power supply and other
noise sources at the common-mode bias node, and
also generates the startup/shutdown DC bias wave-
forms for the speaker amplifiers. Bypass BIAS with a
1µF capacitor to GND.
fier input resistance (R ), forms a highpass filter that
removes the DC bias from an incoming signal (see the
Typical Application Circuit). The AC-coupling capacitor
allows the amplifier to bias the signal to an optimum DC
level. Assuming zero source impedance, the -3dB point
of the highpass filter is given by:
Charge-Pump Capacitor Selection
Use capacitors with an ESR less than 100mΩ for opti-
mum performance. Low-ESR ceramic capacitors mini-
mize the output resistance of the charge pump. For
best performance over the extended temperature
range, select capacitors with an X7R dielectric. Table 6
lists suggested manufacturers.
1
f−3dB
=
2πR C
IN IN
R
is the amplifier’s internal input resistance value
IN
given in the Electrical Characteristics. Choose C such
IN
that f
is well below the lowest frequency of interest.
-3dB
Table 6. Suggested Capacitor Manufacturers
SUPPLIER
Taiyo Yuden
TDK
PHONE
FAX
WEBSITE
800-384-2496
807-803-6100
800-925-0899
847-390-4405
www.t-yuden.com
www.component.tdk.com
22 ______________________________________________________________________________________
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
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, which leads to a loss of
output voltage. Increasing the value of C1 improves load
regulation and reduces the charge-pump output resis-
tance to an extent. See the Output Power vs. Charge-
Pump Capacitance graph in the Typical Operating
Characteristics. Above 2.2µF, the on-resistance of the
switches and the ESR of C1 and C2 dominate.
When considering the use of CPV
in this manner,
SS
note that the charge-pump voltage of CPV is roughly
SS
proportional to CPV
and is not a regulated voltage.
DD
Layout and Grounding
Proper layout and grounding are essential for optimum
performance. Use large traces for the power-supply
inputs and amplifier outputs to minimize losses due to
parasitic trace resistance, as well as route heat away
from the device. Good grounding improves audio per-
formance, minimizes crosstalk between channels, and
prevents any switching noise from coupling into the
audio signal. Connect CPGND, PGND, and GND
together at a single point on the PC board. Route
CPGND and all traces that carry switching transients
away from GND, PGND, and the traces and compo-
nents in the audio signal path.
Output Capacitor (C2)
The output capacitor value and ESR directly affect the
ripple at CPV . Increasing the value of C2 reduces
SS
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. See the Output Power
vs. Charge-Pump Capacitance graph in the Typical
Operating Characteristics.
Connect all components associated with the charge
pump (C2 and C3) to the CPGND plane. Connect V
SS
and CPV
together at the device. Place the charge-
SS
pump capacitors (C1, C2, and C3) as close to the
device as possible. Bypass HPV and PV with a
DD
DD
CPV
Bypass Capacitor
DD
1µF capacitor to GND. Place the bypass capacitors as
close to the device as possible.
The CPV
bypass capacitor (C3) lowers the output
DD
impedance of the power supply and reduces the impact
of the MAX9756/MAX9757/MAX9758’s charge-pump
Use large, low-resistance output traces. As load imped-
ance decreases, the current drawn from the device out-
puts increase. At higher current, the resistance of the
output traces decrease the power delivered to the load.
switching transients. Bypass CPV
with C3, the same
DD
value as C1, and place it physically close to CPV
and
DD
PGND (refer to the MAX9756/MAX9757/MAX9758
Evaluation Kit for a suggested layout).
For example, when compared to a 0Ω trace, a 100mΩ
trace reduces the power delivered to a 4Ω load from
2.1W to 2W. Large output, supply, and GND traces also
improve the power dissipation of the device. The
MAX9756/MAX9757/MAX9758 thin QFN package fea-
tures an exposed thermal pad on its underside. This pad
lowers the package’s thermal resistance by providing a
direct-heat conduction path from the die to the PC
board. Connect the exposed thermal pad to GND by
using a large pad and multiple vias to the GND plane.
Powering Other Circuits
from a Negative Supply
An additional benefit of the MAX9756/MAX9757/
MAX9758 is the internally generated negative supply
voltage (CPV ). CPV
is used by the MAX9756/
SS
SS
MAX9757/MAX9758 to provide the negative supply for
the headphone amplifiers. It can also be used to power
other devices within a design. Current draw from
CPV should be limited to 5mA; exceeding this affects
SS
the operation of the headphone amplifier. A typical
application is a negative supply to adjust the contrast
of LCD modules.
______________________________________________________________________________________ 23
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
MAX9756 Block Diagram
4.5V TO 5.5V
4.5V TO 5.5V
0.1µF
0.1µF
100µF
V
DD
PV
DD
32
9, 19
MAX9756
C
1µF
IN
7
8
OUTL+
OUTL-
GAIN/
VOLUME
1
INL
DR
BTL
AMPLIFIER
LEFT-CHANNEL
AUDIO INPUT
25
35
29
CT
PEAK
DETECT
PREF
0.033µF
180kΩ
C
1µF
IN
21
20
OUTR+
OUTR-
GAIN/
VOLUME
CONTROL
RIGHT-
CHANNEL
AUDIO INPUT
36
INR
BTL
AMPLIFIER
BIAS 26
C
1µF
18
23
HPV
DD
BIAS
0V TO
HPV
28
2
VOL
3V TO 5.5V
VOLUME
AND GAIN
CONTROL
DD
1µF
GAIN1
HPS
V
DD
3
4
GAIN2
GAIN3
HEADPHONE
DETECTION
17 HPL
SHUTDOWN
CONTROL
27
5
SHDN
BEEP
R
B
0.47µF
47kΩ
BEEP
DETECTION
HPR
16
CPV
DD
10
3V TO 5.5V
1µF
11
13
C1P
C1N
C1
1µF
CHARGE
PUMP
CPGND
12
C1
1µF
CPV
V
SS 14
V
DD
SS 15
4.65V OUTPUT TO CODEC
1µF 1µF
REGEN
IN
34
30
24
33
OUT
SET
LDO
C3, C4
1µF
31
6, 22
GND
PGND
FIGURE SHOWN WITH AN ATTACK TIME = 495µs, RELEASE TIME = 990ms AND AN OUTPUT POWER LIMIT SET TO 1.2W, SPKR GAIN = 25.5dB, LDO SHOWN IN FIXED OUTPUT MODE, HPGAIN = 3dB.
24 ______________________________________________________________________________________
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
MAX9757 Block Diagram
4.5V TO 5.5V
4.5V TO 5.5V
0.1µF
0.1µF
100µF
V
PV
DD
DD
29
8, 18
MAX9757
C
1µF
IN
6
7
OUTL+
OUTL-
32
23
GAIN/
VOLUME
INL
DR
BTL
AMPLIFIER
LEFT-CHANNEL
AUDIO INPUT
30
27
CT
PEAK
DETECT
PREF
100µF
180kΩ
C
1µF
IN
20
19
OUTR+
OUTR-
GAIN/
VOLUME
CONTROL
RIGHT-
CHANNEL
AUDIO INPUT
31
INR
BTL
AMPLIFIER
BIAS 26
C
1µF
17
22
HPV
DD
BIAS
0V TO
HPV
28
1
VOL
3V TO 5.5V
VOLUME
AND GAIN
CONTROL
DD
1µF
GAIN1
HPS
V
DD
2
3
GAIN2
GAIN3
HEADPHONE
DETECTION
15 HPL
SHUTDOWN
CONTROL
25
4
SHDN
BEEP
R
B
0.47µF
47kΩ
BEEP
DETECTION
HPR
16
CPV
DD
9
3V TO 5.5V
1µF
10
12
C1P
C1N
C1
1µF
CHARGE
PUMP
CPGND
11
C2
1µF
CPV
V
SS 13
SS 14
28
5, 21
PGND
GND
FIGURE SHOWN WITH AN ATTACK TIME = 495µs, RELEASE TIME = 990ms AND AN OUTPUT POWER LIMIT SET TO 1.2W, SPKR GAIN = 25.5dB, HP GAIN = 3dB.
______________________________________________________________________________________ 25
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
MAX9758 Block Diagram
4.5V TO 5.5V
4.5V TO 5.5V
0.1µF
0.1µF
100µF
V
DD
PV
DD
29
8, 18
MAX9758
C
1µF
IN
6
7
OUTL+
OUTL-
32
INL
BTL
AMPLIFIER
LEFT-CHANNEL
AUDIO INPUT
VOLUME
C
1µF
IN
20
19
OUTR+
OUTR-
31
INR
RIGHT-CHANNEL
AUDIO INPUT
BTL
AMPLIFIER
VOLUME
BIAS 24
C
1µF
17
22
HPV
DD
BIAS
0V TO
HPV
26
1
VOL
3V TO 5.5V
VOLUME
AND GAIN
CONTROL
DD
1µF
GAIN1
HPS
V
DD
2
3
GAIN2
GAIN3
HEADPHONE
DETECTION
15 HPL
SHUTDOWN
CONTROL
25
4
SHDN
BEEP
0.47µF
R
B
BEEP
DETECTION
HPR
16
CPV
DD
9
3V TO 5.5V
1µF
10
12
C1P
C1N
C1
1µF
CHARGE
PUMP
CPGND
11
C2
1µF
CPV
V
SS 13
3.3V OUTPUT TO CODEC
SS 14
30
27
OUT
SET
REGEN
23
LDO
82kΩ
47kΩ
V
10pF
DD
1µF
1µF
28
5, 21
GND
PGND
FIGURE SHOWN WITH SPKR GAIN = 25.5dB, LDO SHOWN IN ADJUSTABLE OUTPUT MODE SET TO 3.3V, HP GAIN = 3dB.
26 ______________________________________________________________________________________
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
System Diagram
4.5V TO 5.5V 3V TO 5.5V
10µF
1µF
V
DD
PV
DD
HPV
DD
IN
OUTL+
OUTL-
REGEN
INL
1µF
1µF
1µF
MAX9756
CODEC
INR
OUTR+
OUTR-
OUT
1µF
47kΩ
BEEP
HPL
SHDN
GAIN1
HPS
HPR
µC
GAIN2
GAIN3
HPV
DD
DR
VOL
3V TO 5.5V
1µF
CPV
C1P
DD
CPV
SS
SS
V
1µF
1µF
C1N
SET
PREF
BIAS
CT
CPGND
180kΩ
BIAS
1µF
0.1µF
0.033µF
GND
PGND
______________________________________________________________________________________ 27
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
Pin Configurations
TOP VIEW
26 25
23
27
24
22
21 20 19
VOL 28
PREF 29
SET 30
GND 31
18 HPV
17 HPL
16 HPR
DD
15
V
SS
V
32
33
14 CPV
13 C1N
DD
SS
MAX9756
IN
OUT 34
CT 35
INR 36
12 CPGND
C1P
10 CPV
11
DD
2
3
5
7
8
9
1
4
6
TQFN
6mm x 6mm
24 23 22 21 20 19 18 17
24 23 22 21 20 19 18 17
16
15
14
13
12
25
HPL
HPR
16
15
14
13
12
SHDN
SHDN 25
VOL 26
HPL
HPR
VOL 26
V
SS
27
28
29
30
31
32
V
SS
SET
27
28
29
30
31
32
PREF
GND
CPV
CPV
SS
GND
SS
MAX9758
MAX9757
V
C1N
V
C1N
DD
DD
11 CPGND
OUT
INR
INL
11 CPGND
CT
INR
INL
10
9
C1P
CPV
10
9
C1P
CPV
DD
DD
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
THIN QFN
5mm x 5mm
THIN QFN
5mm x 5mm
Chip Information
PROCESS: BICMOS
28 ______________________________________________________________________________________
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
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.)
D2
D
b
0.10 M
C A B
C
L
D2/2
D/2
k
L
MARKING
AAAAA
E/2
E2/2
C
(NE-1) X
e
L
E2
E
PIN # 1 I.D.
0.35x45°
DETAIL A
e/2
PIN # 1
I.D.
e
(ND-1) X
e
DETAIL B
e
L
C
L
C
L
L1
L
L
e
e
0.10
C
A
0.08
C
C
A3
A1
PACKAGE OUTLINE,
16, 20, 28, 32, 40L THIN QFN, 5x5x0.8mm
1
-DRAWING NOT TO SCALE-
I
21-0140
2
______________________________________________________________________________________ 29
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
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
EXPOSED PAD VARIATIONS
PKG.
SYMBOL MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX.
DOWN
BONDS
ALLOWED
16L 5x5
20L 5x5
28L 5x5
32L 5x5
40L 5x5
L
D2
E2
exceptions
PKG.
CODES
±0.15
MIN. NOM. MAX.
MIN. NOM. MAX.
A
0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80
0.02 0.05 0.02 0.05 0.02 0.05 0.02 0.05 0.02 0.05
0.20 REF. 0.20 REF. 0.20 REF. 0.20 REF. 0.20 REF.
T1655-2
T1655-3
3.00 3.10 3.20 3.00 3.10 3.20
3.00 3.10 3.20 3.00 3.10 3.20
T1655N-1 3.00 3.10 3.20 3.00 3.10 3.20
YES
NO
NO
**
**
**
**
A1
0
0
0
0
0
A3
b
0.25 0.30 0.35 0.25 0.30 0.35 0.20 0.25 0.30 0.20 0.25 0.30 0.15 0.20 0.25
4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10
4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10
T2055-3
T2055-4
T2055-5
T2855-3
3.00 3.10 3.20 3.00 3.10 3.20
3.00 3.10 3.20 3.00 3.10 3.20
YES
NO
D
E
**
YES
3.15 3.25 3.35 3.15 3.25 3.35 0.40
e
0.80 BSC.
0.25
0.65 BSC.
0.25
0.50 BSC.
0.25
0.50 BSC.
0.25
0.40 BSC.
3.15 3.25 3.35 3.15 3.25 3.35
**
YES
YES
NO
k
-
-
-
-
-
-
-
-
0.25 0.35 0.45
T2855-4
T2855-5
2.60 2.70 2.80 2.60 2.70 2.80
2.60 2.70 2.80 2.60 2.70 2.80
3.15 3.25 3.35 3.15 3.25 3.35
**
**
L
0.30 0.40 0.50 0.45 0.55 0.65 0.45 0.55 0.65 0.30 0.40 0.50 0.40 0.50 0.60
L1
-
-
-
-
-
-
-
-
-
-
-
-
0.30 0.40 0.50
NO
YES
YES
T2855-6
T2855-7
**
**
N
ND
NE
16
4
4
20
5
5
28
7
7
32
8
8
40
10
10
2.80
2.60 2.70
2.60 2.70 2.80
T2855-8
3.15 3.25 3.35 3.15 3.25 3.35 0.40
WHHB
WHHC
WHHD-1
WHHD-2
-----
JEDEC
T2855N-1 3.15 3.25 3.35 3.15 3.25 3.35
NO
YES
NO
YES
NO
**
**
**
**
**
**
3.20
3.00 3.10 3.20
T3255-3
T3255-4
T3255-5
3.00 3.10
3.00 3.10 3.20 3.00 3.10 3.20
3.20
NOTES:
3.00 3.10
3.00 3.10 3.20
1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994.
2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES.
3. N IS THE TOTAL NUMBER OF TERMINALS.
T3255N-1 3.00 3.10 3.20 3.00 3.10 3.20
T4055-1 3.20 3.30 3.40 3.20 3.30 3.40
YES
**SEE COMMON DIMENSIONS TABLE
4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL
CONFORM TO JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE
OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE TERMINAL #1
IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE.
5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN
0.25 mm AND 0.30 mm FROM TERMINAL TIP.
6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY.
7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION.
8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS.
9. DRAWING CONFORMS TO JEDEC MO220, EXCEPT EXPOSED PAD DIMENSION FOR
T2855-3 AND T2855-6.
10. WARPAGE SHALL NOT EXCEED 0.10 mm.
11. MARKING IS FOR PACKAGE ORIENTATION REFERENCE ONLY.
12. NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY.
13. LEAD CENTERLINES TO BE AT TRUE POSITION AS DEFINED BY BASIC DIMENSION "e", ±0.05.
PACKAGE OUTLINE,
16, 20, 28, 32, 40L THIN QFN, 5x5x0.8mm
2
-DRAWING NOT TO SCALE-
21-0140
I
2
30 ______________________________________________________________________________________
2.3W Stereo Speaker Amplifiers and DirectDrive
Headphone Amplifiers with Automatic Level Control
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.)
(NE-1) X
e
E
E/2
k
D/2
C
(ND-1) X
e
D
D2
L
D2/2
e
b
E2/2
L
C
L
k
E2
e
L
C
C
L
L
L1
L
L
e
e
A
A1
A2
PACKAGE OUTLINE
36, 40, 48L THIN QFN, 6x6x0.8mm
1
F
21-0141
2
NOTES:
1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994.
2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES.
3. N IS THE TOTAL NUMBER OF TERMINALS.
4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JESD 95-1
SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE
ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE.
5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.25 mm AND 0.30 mm
FROM TERMINAL TIP.
6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY.
7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION.
8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS.
9. DRAWING CONFORMS TO JEDEC MO220, EXCEPT FOR 0.4mm LEAD PITCH PACKAGE T4866-1.
10. WARPAGE SHALL NOT EXCEED 0.10 mm.
11. MARKING IS FOR PACKAGE ORIENTATION REFERENCE ONLY.
12. NUMBER OF LEADS SHOWN FOR REFERENCE ONLY.
PACKAGE OUTLINE
36, 40, 48L THIN QFN, 6x6x0.8mm
2
F
21-0141
2
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 31
© 2006 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
Quijano
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