MAX9750_V01 [MAXIM]
2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers;
| 型号： | MAX9750_V01 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 2.6W Stereo Audio Power Amplifiers and DirectDrive Headphone Amplifiers |
| 文件： | 总30页 (文件大小：481K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-3006; Rev 8; 6/08
EVALUATION KIT
AVAILABLE
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
01/MAX975
General Description
Features
The MAX9750/MAX9751/MAX9755 combine a stereo,
2.6W audio power amplifier and stereo DirectDrive®
110mW headphone amplifier in a single device. The
headphone amplifier uses Maxim’s DirectDrive architec-
ture that produces a ground-referenced output from a
single supply, eliminating the need for large DC-blocking
capacitors, saving cost, space, and component height.
A high 90dB PSRR and low 0.01% THD+N ensures
clean, low-distortion amplification of the audio signal.
♦ No DC-Blocking Capacitors Required—Provides
Industry’s Most Compact Notebook Audio
Solution
♦ PC2001 Compliant
♦ 5V Single-Supply Operation
♦ Class AB 2.6W Stereo BTL Speaker Amplifiers
♦ 110mW DirectDrive Headphone Amplifiers
♦ High 90dB PSRR
♦ Low-Power Shutdown Mode
♦ Industry-Leading Click-and-Pop Suppression
♦ Low 0.01% THD+N at 1kHz
♦ Short-Circuit and Thermal Protection
♦ Selectable Gain Settings
♦ Analog Volume Control (MAX9750)
♦ BEEP Input with Glitch Filter (MAX9750)
♦ 2:1 Stereo Input MUX (MAX9751)
The MAX9750 features an analog volume control, and a
BEEP input. The MAX9751 features a 2:1 input multiplexer,
allowing multiple audio sources to be selected. All devices
feature a single-supply voltage, a shutdown mode, logic-
selectable gain, and a headphone sense input. Industry-
leading click-and-pop suppression eliminates audible
transients during power and shutdown cycles.
The MAX9750/MAX9751/MAX9755 are offered in a
space-saving, thermally efficient 28-pin thin QFN (5mm
x 5mm x 0.8mm) package. These devices have thermal-
overload and output short-circuit protection, and are
specified over the extended -40°C to +85°C tempera-
ture range.
Applications
♦
8kV ESD-Protected Headphone Driver Outputs
Notebook PCs
Tablet PCs
Flat-Panel TVs
♦ Available in Space-Saving, Thermally Efficient
PC Displays
28-Pin Thin QFN (5mm x 5mm x 0.8mm) Package
Portable DVD Players LCD Projectors
Ordering Information
Simplified Block Diagrams
PIN-
PACKAGE
MAXIMUM GAIN
(dB)
PART*
MAX9750AETI+
MAX9750BETI+
MAX9750CETI+
MAX9751ETI+
MAX9755ETI+
28 Thin QFN
28 Thin QFN
28 Thin QFN
28 Thin QFN
28 Thin QFN
13.5
19.5
10.5
10.5
10.5
+Denotes a lead-free/RoHS-compliant package.
*All devices specified over the -40°C to +85°C temperature
range.
VOL
DirectDrive is a registered trademark of Maxim Integrated
Products, Inc.
BEEP
MAX9750
Simplified Block Diagrams continued at end of data sheet.
________________________________________________________________ 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.
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (V , PV , HPV , CPV to GND)..........+6V
DD
Continuous Input Current (All Other Pins) ........................±ꢁ±mA
DD
DD
DD
GND to PGND.....................................................................±±.ꢀV
Continuous Power Dissipation (T = +7±°C, multilayer board)
ꢁ8-Pin Thin QFN (derate ꢁꢀ.8mW/°C above +7±°C) .19±±mW
A
CPV , C1N, V to GND .........................-6.±V to (GND + ±.ꢀV)
SS
SS
HPOUT_ to GND....................................................................±ꢀV
Junction-to-Case Thermal Resistance (θ
)
JC
Any Other Pin .............................................-±.ꢀV to (V + ±.ꢀV)
ꢁ8-Pin Thin QFN...........................................................ꢁ4°C/W
Junction Temperature......................................................+15±°C
Operating Temperature Range ...........................-4±°C to +85°C
Storage Temperature Range.............................-65°C to +15±°C
Lead Temperature (soldering, 1±s) .................................+ꢀ±±°C
DD
Duration of OUT_ Short Circuit to GND or PV ........Continuous
DD
Duration of OUT_+ Short Circuit to OUT_-.................Continuous
Duration of HPOUT_ Short Circuit to GND,
V
SS
or HPV .........................................................Continuous
DD
Continuous Current (PV , OUT_, PGND) ...........................1.7A
DD
Continuous Current (CPV , C1N, C1P, CPV , V , HPV ,
DD
SS SS
DD
HPOUT_).......................................................................85±mA
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
= CPV
= HPV
= 5V, V
= V
= V
= ±V, SHDN = V , C
= 1µF, C1 = Cꢁ = 1µF, speaker load
DD
DD
DD
GND
PGND
CPGND
DD
BIAS
terminated between OUT_+ and OUT_-, headphone load terminated between HPOUT_ and GND, V
= V
= V
= V
= ±V,
GAIN1
GAINꢁ
VOL
GAIN
T = T
to T , unless otherwise noted. Typical values are at T = +ꢁ5°C.) (Note 1)
MAX A
A
MIN
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
GENERAL
Supply Voltage Range
V
, PV
Inferred from PSRR test
Inferred from PSRR test
HPS = GND, speaker mode, R = ∞
4.5
ꢀ.±
5.5
5.5
V
V
DD
DD
CPV
,
DD
Headphone Supply Voltage
Quiescent Supply Current
HPV
DD
14
7
ꢁ9
1ꢀ
5
L
9
I
mA
DD
HPS = V , headphone mode, R = ∞
DD
L
Shutdown Supply Current
Bias Voltage
I
SHDN = GND
±.ꢁ
µA
V
SHDN
V
1.7
1.8
1±
ꢁ±
6
1.9
BIAS
Switching Time
t
Gain or input switching
µs
SW
MAX975±
MAX9751/MAX9755
1±
ꢀ±
8.±
Amplifier inputs
(Note ꢁ)
Input Resistance
Turn-On Time
R
IN
kΩ
4.5
t
ꢁ5
ms
SON
SPEAKER AMPLIFIER (HPS = GND)
Measured
between OUT_+ MAX9751/MAX9755
and OUT_-,
MAX975±A/MAX975±B/
1
±.4
9±
15
6
Output Offset Voltage
V
mV
dB
OS
MAX975±C
T
= +ꢁ5°C
A
MAX975±A/MAX975±B/
MAX975±C/MAX9751
PV
or V
=
DD
DD
75
7ꢁ
4.5V to 5.5V
(T = +ꢁ5°C)
A
Power-Supply Rejection Ratio
(Note ꢀ)
MAX9755
9±
8±
55
PSRR
f = 1kHz, V
= ꢁ±±mV
P-P
RIPPLE
f = 1±kHz, V
= ꢁ±±mV
P-P
RIPPLE
2
_______________________________________________________________________________________
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
01/MAX975
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= PV
= CPV
= HPV
= 5V, V
= V
= V
= ±V, SHDN = V , C
= 1µF, C1 = Cꢁ = 1µF, speaker load
DD
DD
DD
GND
PGND
CPGND
DD
BIAS
terminated between OUT_+ and OUT_-, headphone load terminated between HPOUT_ and GND, V
= V
= V
= V
= ±V,
GAIN1
MIN
±.9
GAINꢁ
TYP
1.4
VOL
GAIN
T = T
to T , unless otherwise noted. Typical values are at T = +ꢁ5°C.) (Note 1)
MAX A
A
MIN
PARAMETER
SYMBOL
CONDITIONS
MAX
UNITS
MAX975±A/
MAX975±B/
MAX9751/
MAX9755
R = 8Ω
L
MAX975±C
±.65
±.8
MAX975±A/
MAX975±B/
MAX9751/
MAX9755
THD+N = 1%,
f = 1kHz,
ꢁ.ꢀ
Output Power (Note 4)
P
R = 4Ω
L
W
OUT
T
= +ꢁ5°C
A
MAX975±C
1.ꢁ
1.5
ꢁ.6
MAX975±A/
MAX975±B/
MAX9751/
MAX9755
R = ꢀΩ
L
MAX975±C
ꢁ.ꢁ
R = 8Ω, P
= 5±±mW, f = 1kHz
= 1W, f = 1kHz
±.±1
±.±ꢁ
L
OUT
OUT
OUT
Total Harmonic Distortion Plus
Noise
THD+N
SNR
%
R = 4Ω, P
L
R = 8Ω, P
= 5±±mW, BW = ꢁꢁHz to
L
Signal-to-Noise Ratio
96
dB
ꢁꢁkHz
Noise
V
BW = ꢁꢁHz to ꢁꢁkHz, A-weighted
No sustained oscillations
ꢁꢁ
ꢁ±±
75
µV
n
RMS
Capacitive-Load Drive
Crosstalk
C
L
pF
L to R, R to L, f = 1±kHz
dB
Any unselected input to any active input,
f = 1±kHz (MAX9751), input referred
Off-Isolation
Slew Rate
75
SR
1.4
9
V/µs
GAIN1 = ±, GAINꢁ = ±
GAIN1 = 1, GAINꢁ = ±
1±.5
1ꢁ
MAX975±A
GAIN1 = ±, GAINꢁ = 1
GAIN1 = 1, GAINꢁ = 1
GAIN1 = ±, GAINꢁ = ±
GAIN1 = 1, GAINꢁ = ±
1ꢀ.5
15
16.5
18
MAX975±B
Gain (Maximum Volume Setting)
A
dB
VMAX(SPKR)
GAIN1 = ±, GAINꢁ = 1
GAIN1 = 1, GAINꢁ = 1
GAIN1 = ±, GAINꢁ = ±
19.5
6
GAIN1 = 1, GAINꢁ = ±
MAX975±C
7.5
GAIN1 = ±, GAINꢁ = 1
9
GAIN1 = 1, GAINꢁ = 1
1±.5
9
GAIN = 1
GAIN = ±
Gain (MAX9751/MAX9755)
A
dB
V
1±.5
_______________________________________________________________________________________
3
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= PV
= CPV
= HPV
= 5V, V
= V
= V
= ±V, SHDN = V , C
= 1µF, C1 = Cꢁ = 1µF, speaker load
DD
DD
DD
GND
PGND
CPGND
DD
BIAS
terminated between OUT_+ and OUT_-, headphone load terminated between HPOUT_ and GND, V
= V
= V
= V
= ±V,
GAIN1
GAINꢁ
VOL
GAIN
T = T
to T , unless otherwise noted. Typical values are at T = +ꢁ5°C.) (Note 1)
MAX A
A
MIN
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
HEADPHONE AMPLIFIER (HPS = V
)
DD
Output Offset Voltage
V
T
= +ꢁ5°C
A
ꢁ
75
7ꢀ
6ꢀ
7
mV
dB
OS
HPV
= ꢀV to 5.5V, T = +ꢁ5°C
6±
4±
DD
A
Power-Supply Rejection Ratio
(Note ꢀ)
PSRR
f = 1kHz, V
= ꢁ±±mV
P-P
RIPPLE
f = 1±kHz, V
= ꢁ±±mV
P-P
RIPPLE
R = ꢀꢁΩ
5±
L
THD+N = 1%,
f = 1kHz, T = +ꢁ5°C
Output Power
P
mW
OUT
A
R = 16Ω
L
11±
R = ꢀꢁΩ, P
= ꢁ±mW, f = 1kHz
±.±±7
±.±ꢀ
L
OUT
Total Harmonic Distortion Plus
Noise
THD+N
SNR
%
R = 16Ω, P
= 75mW, f = 1kHz
L
OUT
R = ꢀꢁΩ, P
= 5±mW, BW = ꢁꢁHz to
L
OUT
Signal-to-Noise Ratio
1±1
dB
ꢁꢁkHz
Noise
V
BW = ꢁꢁHz to ꢁꢁkHz
11
ꢁ±±
88
µV
RMS
n
Capacitive-Load Drive
Crosstalk
C
No sustained oscillations
L to R, R to L, f = 1±kHz
pF
L
dB
Any unselected input to any active input,
f = 1±kHz (MAX9751), input referred
Off-Isolation
74
Slew Rate
ESD
SR
±.4
±8
ꢀ
V/µs
kV
01/MAX975
ESD
IEC air discharge
GAINꢁ = GAIN = ±, GAIN1 = X
GAINꢁ = GAIN = 1, GAIN1 = X
Gain
A
dB
V
±
CHARGE PUMP
Charge-Pump Frequency
VOLUME CONTROL (MAX9750_)
VOL Input Impedance
VOL Input Hysteresis
f
5±±
55±
6±±
kHz
OSC
R
1±±
1±
MΩ
VOL
mV
±.858 x
HPV
Full Mute Input Voltage
(Note 5)
V
DD
Channel Matching
A
R
= -ꢁ5dB to +1ꢀ.5dB
±.ꢁ
dB
V
B
BEEP INPUT (MAX9750_)
Beep Signal Minimum Amplitude
Beep Signal Minimum Frequency
V
= ꢀꢀkΩ (Note 6)
±.8
V
P-P
BEEP
f
ꢀ±±
Hz
BEEP
4
_______________________________________________________________________________________
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
01/MAX975
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= PV
= CPV
= HPV
= 5V, V
= V
= V
= ±V, SHDN = V , C
= 1µF, C1 = Cꢁ = 1µF, speaker load
DD
DD
DD
GND
PGND
CPGND
DD
BIAS
terminated between OUT_+ and OUT_-, headphone load terminated between HPOUT_ and GND, V
= V
= V
= V
= ±V,
GAIN1
MIN
ꢁ
GAINꢁ
VOL
GAIN
T = T
to T , unless otherwise noted. Typical values are at T = +ꢁ5°C.) (Note 1)
MAX A
A
MIN
PARAMETER
SYMBOL
CONDITIONS
TYP
MAX
UNITS
LOGIC INPUT (SHDN, GAIN1, GAIN2, GAIN, VOL, IN1/2)
Logic Input High Voltage
Logic Input Low Voltage
Logic Input Current
V
V
V
IH
V
±.8
1
IL
I
µA
IN
LOGIC INPUT HEADPHONE (HPS)
Logic Input High Voltage
Logic Input Low Voltage
Logic Input Current
V
ꢁ
V
V
IH
V
±.8
IL
I
1±
µA
IN
Note 1: All devices are 1±±% production tested at room temperature. All temperature limits are guaranteed by design.
Note 2: Guaranteed by design. Not production tested.
Note 3: PSRR is specified with the amplifier input connected to GND through C
.
IN
Note 4: Output power levels are measured with the thin QFN’s exposed paddle soldered to the ground plane.
Note 5: See Table ꢀ for details of the mute levels.
Note 6: The value of R dictates the minimum beep signal amplitude (see the Beep Input section).
B
_______________________________________________________________________________________
5
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Typical Operating Characteristics
(Measurement BW = ꢁꢁHz to ꢁꢁkHz, T = +ꢁ5°C, unless otherwise noted.)
A
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (SPEAKER MODE)
TOTAL HARMONIC DISTORTION PLUS NOISE
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (SPEAKER MODE)
vs. FREQUENCY (SPEAKER MODE)
10
1
10
1
10
1
V
CC
= 5V
V
CC
= 5V
V
= 5V
CC
R = 8Ω
R = 4Ω
R = 3Ω
L
L
L
A
V
= 10.5dB
A
= 10.5dB
A
= 10.5dB
V
V
OUTPUT POWER = 1.25W
OUTPUT POWER = 1.5W
OUTPUT POWER = 100mW
OUTPUT POWER = 600mW
0.1
0.01
0.1
0.01
0.1
0.01
OUTPUT POWER = 500mW
OUTPUT POWER = 500mW
0.001
0.001
0.001
0.0001
0.0001
0.0001
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
10
1
100
10
1
V
A
= 5V
= 13.5dB
DD
V
V
= 5V
V
= 5V
CC
CC
L
V
R = 4Ω
R = 3Ω
A
MAX9750C
L
R = 3Ω
L
A
V
= 10.5dB
= 10.5dB
10
1
MAX9750C
f = 10kHz
f = 1kHz
01/MAX975
f
= 10kHz
f
IN
= 10kHz
IN
0.1
0.1
0.1
0.01
0.001
0.01
0.01
f = 20Hz
f
= 1kHz
2.0
f
= 1kHz
IN
IN
f
= 20Hz
IN
f
= 20Hz
IN
0.001
0.001
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
2.5
3.0
0
2.0
0.5
1.0
OUTPUT POWER (W)
1.5
OUTPUT POWER (W)
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
10
1
V
A
= 5V
DD
V
= 5V
V
A
= 5V
= 13.5dB
CC
DD
V
= 13.5dB
R = 8Ω
V
L
R = 8Ω
L
A
V
= 10.5dB
R = 4Ω
L
10
10
MAX9750C
1
1
f = 10kHz
f = 1kHz
f = 10kHz
0.1
f = 1kHz
0.1
f = 10kHz
IN
0.1
0.01
0.001
0.01
0.001
0.01
f = 20Hz
1.0
f
= 1kHz
0.8
IN
f
= 20Hz
f = 20Hz
0.5
OUTPUT POWER (W)
IN
0.001
0
1.0
1.5
0
1.2
0
0.5
1.5
2.0
2.5
3.0
0.2
0.4
0.6
1.0
OUTPUT POWER (W)
OUTPUT POWER (W)
6
_______________________________________________________________________________________
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
01/MAX975
Typical Operating Characteristics (continued)
(Measurement BW = ꢁꢁHz to ꢁꢁkHz, T = +ꢁ5°C, unless otherwise noted.)
A
OUTPUT POWER
vs. LOAD RESISTANCE (SPEAKER MODE)
OUTPUT POWER
vs. LOAD RESISTANCE (SPEAKER MODE)
3.0
2.5
2.0
1.5
1.0
0.5
0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
V
= 5V
CC
f = 1kHz
= 10.5dB
A
V
THD+N = 10%
MAX9750C
THD+N = 10%
THD+N = 1%
THD+N = 1%
1
10
LOAD RESISTANCE (Ω)
100
1
10
100
LOAD RESISTANCE (Ω)
POWER DISSIPATION vs. OUTPUT POWER
(SPEAKER MODE)
POWER DISSIPATION vs. OUTPUT POWER
(SPEAKER MODE)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY (SPEAKER MODE)
5
4
3
2
1
0
5
4
3
2
1
0
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
V
A
= 200mV
P-P
= 10.5dB
RIPPLE
V
V
= 5V
V
DD
= 5V
DD
f = 1kHz
= P
f = 1kHz
= P
OUTPUT REFERRED
P
+ P
OUTR
P
+ P
OUTL OUTR
OUT
OUTL
OUT
MAX9750C
R = 4Ω
L
R = 4Ω
L
R = 8Ω
L
R = 8Ω
L
0
1
2
3
4
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
OUTPUT POWER (W)
TURN-ON RESPONSE
(SPEAKER MODE)
CROSSTALK vs. FREQUENCY
(SPEAKER MODE)
MAX9750/51 toc16
0
V
V
= 5V
CC
-10
-20
-30
-40
-50
-60
-70
-80
= 200mV
5V/div
RIPPLE
P-P
R = 4Ω
L
SHDN
OUT_+
AND
OUT_-
2V/div
LEFT TO RIGHT
RIGHT TO LEFT
-90
OUT_+
- OUT_-
100mV/div
-100
-110
-120
R
= 8Ω
L
10
100
1k
10k
100k
20ms/div
FREQUENCY (Hz)
_______________________________________________________________________________________
7
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Typical Operating Characteristics (continued)
(Measurement BW = ꢁꢁHz to ꢁꢁkHz, T = +ꢁ5°C, unless otherwise noted.)
A
TURN-OFF RESPONSE
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY (HEADPHONE MODE)
(SPEAKER MODE)
MAX9750/51 toc17
10
1
V
= 5V
DD
R = 16Ω
5V/div
L
A
V
= 3dB
SHDN
OUTPUT POWER = 90mW
OUT_+
AND
OUT_-
0.1
0.01
2V/div
OUTPUT POWER = 30mW
OUT_+
- OUT_-
20mV/div
0.001
R
= 8Ω
L
0.0001
10
100
1k
10k
100k
20ms/div
FREQUENCY (Hz)
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
1
10
1
10
1
V
= 5V
V
= 3.3V
DD
V
DD
= 3.3V
DD
R = 32Ω
R = 16Ω
R = 32Ω
L
L
L
A
V
= 3dB
A = 3dB
V
A
V
= 3dB
OUTPUT POWER = 30mW
OUTPUT POWER = 45mW
OUTPUT POWER = 45mW
0.1
0.01
0.1
0.01
0.1
01/MAX975
0.01
OUTPUT POWER = 10mW
OUTPUT POWER = 10mW
OUTPUT POWER = 10mW
0.001
0.001
0.001
0.0001
0.0001
0.0001
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. OUTPUT POWER (HEADPHONE MODE)
1000
100
10
1000
100
10
1000
100
10
V
DD
= 5V
V
DD
= 5V
V
DD
= 3.3V
R = 16Ω
R = 32Ω
R = 16Ω
L
L
L
A
V
= 3dB
A
= 3dB
A = 3dB
V
V
f
IN
= 1kHz
f
IN
= 1kHz
1
1
1
f
IN
= 10kHz
f
IN
= 10kHz
f
IN
= 10kHz
0.1
0.1
0.1
f
IN
= 20Hz
0.01
0.001
0.01
0.001
0.01
0.001
f
= 1kHz
100
IN
f
IN
= 20Hz
20
10
40
OUTPUT POWER (mW)
0
25
50
75
125
150
0
40
60
80
100
0
20
30
50
60
OUTPUT POWER (mW)
OUTPUT POWER (mW)
8
_______________________________________________________________________________________
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
01/MAX975
Typical Operating Characteristics (continued)
(Measurement BW = ꢁꢁHz to ꢁꢁkHz, T = +ꢁ5°C, unless otherwise noted.)
A
POWER DISSIPATION vs. OUTPUT POWER
(HEADPHONE MODE)
OUTPUT POWER vs. LOAD RESISTANCE
(HEADPHONE MODE)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER (HEADPHONE MODE)
250
225
200
175
150
125
100
75
1000
100
10
180
160
140
120
100
80
V
= 3.3V
DD
R = 32Ω
L
THD+N = 10%
R = 16
L
Ω
A
= 3dB
V
f
IN
= 1kHz
1
f
IN
= 10kHz
R = 32
L
Ω
0.1
0.01
60
40
V
= 5V
50
DD
THD+N = 1%
f = 1kHz
= P
20
25
P
+ P
OUTR
OUT
OUTL
0
0.001
0
0
25 50 75 100 125 150 175 200 225 250
OUTPUT POWER (mW)
40 50
OUTPUT POWER (mW)
90
10
100
1000
0
10 20 30
60 70 80
LOAD RESISTANCE (Ω)
OUTPUT POWER vs. SUPPLY VOLTAGE
(HEADPHONE MODE)
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY (HEADPHONE MODE)
125
100
75
50
25
0
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
V
A
= 200mV
P-P
= 10.5dB
RIPPLE
V
R = 16Ω
L
OUTPUT REFERRED
R = 32Ω
L
f = 1kHz
3.0
3.5
4.0
4.5
5.0
5.5
10
100
1k
10k
100k
CROSSTALK vs. FREQUENCY
(HEADPHONE MODE)
OUTPUT POWER vs. CHARGE-PUMP
CAPACITANCE AND LOAD RESISTANCE
0
200
180
160
140
120
100
80
V
V
= 5V
V
DD
= 5V
CC
= 200mV
f = 1kHz
THD+N = 1%
RIPPLE
P-P
-20
-40
R = 32Ω
L
C1 = C2 = 2.2μF
-60
-80
60
RIGHT TO LEFT
C1 = C2 = 1μF
40
-100
-120
20
LEFT TO RIGHT
0
10
100
1k
10k
100k
10
20
30
40
50
FREQUENCY (Hz)
LOAD RESISTANCE (Ω)
_______________________________________________________________________________________
9
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Typical Operating Characteristics (continued)
(Measurement BW = ꢁꢁHz to ꢁꢁkHz, T = +ꢁ5°C, unless otherwise noted.)
A
TURN-ON RESPONSE
(HEADPHONE MODE)
HEADPHONE OUTPUT SPECTRUM
MAX9750/51 toc33
0
V
DD
= 5V
f = 1kHz
= -60dB
R = 32Ω
L
5V/div
-20
-40
V
OUT
SHDN
-60
-80
20mV/div
HPOUT_
-100
-120
-140
R
= 32Ω
L
0
5
10
15
20
10ms/div
FREQUENCY (Hz)
TURN-OFF RESPONSE
(HEADPHONE MODE)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX9750/51 toc34
18
16
14
12
10
5V/div
HPS = GND
SHDN
HPS = V
DD
01/MAX975
8
6
4
2
0
20mV/div
HPOUT_
R
= 32Ω
L
4.50
4.75
5.00
5.25
5.50
10ms/div
SUPPLY VOLTAGE (V)
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
4.50
4.75
5.00
5.25
5.50
SUPPLY VOLTAGE (V)
10 ______________________________________________________________________________________
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
01/MAX975
Pin Description
PIN
MAX9751
—
NAME
FUNCTION
MAX9750
MAX9755
1
ꢁ
ꢁ
INL
Left-Channel Audio Input
Audible Alert Beep Input
—
—
BEEP
Power Ground. Connect PGND to GND at a single point on the PCB near
the device.
ꢀ, 19
ꢀ, 19
ꢀ, 19
PGND
4
5
4
5
4
5
OUTL+
OUTL-
Left-Channel Positive Speaker Output
Left-Channel Negative Speaker Output
Speaker Amplifier Power Supply
6, 16
7
6, 16
7
6, 16
7
PV
DD
CPV
Charge-Pump Power Supply
DD
8
8
8
C1P
Charge-Pump Flying-Capacitor Positive Terminal
Charge-Pump Ground. Connect CPGND to PGND.
Charge-Pump Flying-Capacitor Negative Terminal
9
9
9
CPGND
C1N
1±
11
1ꢁ
1ꢀ
14
15
17
18
ꢁ±
ꢁ1
1±
11
1ꢁ
1ꢀ
14
15
17
18
ꢁ±
ꢁ1
1±
11
1ꢁ
1ꢀ
14
15
17
18
ꢁ±
ꢁ1
CPV
Charge-Pump Output. Connect to V
.
SS
SS
V
Headphone Amplifier Negative Power Supply
Right-Channel Headphone Output
SS
HPOUTR
HPOUTL
Left-Channel Headphone Output
HPV
Headphone Positive Power Supply
DD
OUTR-
OUTR+
HPS
Right-Channel Negative Speaker Output
Right-Channel Positive Speaker Output
Headphone Sense Input
BIAS
Common-Mode Bias Voltage. Bypass with a 1µF capacitor to GND.
Shutdown. Drive SHDN low to disable the device. Connect SHDN to V
for normal operation.
DD
ꢁꢁ
ꢁꢁ
ꢁꢁ
SHDN
ꢁꢀ
ꢁ4
ꢁ5
—
—
ꢁ5
—
—
ꢁ5
GAINꢁ
GAIN1
Gain Control Input ꢁ
Gain Control Input 1
Power Supply
V
DD
Ground. Connect GND to PGND at a single point on the PCB near the
device.
ꢁ6
ꢁ6
ꢁꢀ, ꢁ6
GND
ꢁ7
ꢁ8
—
—
—
—
—
—
—
—
EP
—
—
1
ꢁ8
—
INR
VOL
INL1
INLꢁ
IN1/2
GAIN
INR1
INRꢁ
N.C.
N.C.
EP
Right-Channel Audio Input
Analog Volume Control Input
Left-Channel Audio Input 1
Left-Channel Audio Input ꢁ
Input Select
—
ꢁ
—
ꢁꢀ
ꢁ4
ꢁ7
ꢁ8
—
—
EP
—
ꢁ4
Gain Select
—
Right-Channel Audio Input 1
Right-Channel Audio Input ꢁ
No Connection. Not internally connected.
No Connection. Not internally connected.
Exposed Paddle. Connect to GND.
—
1, ꢁ7
1, ꢁ7
EP
______________________________________________________________________________________ 11
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
MAX9750 ONLY
IN_
V
DD
V
OUT
V
/2
DD
GND
OUT_+
BIAS
BIAS
CONVENTIONAL DRIVER-BIASING SCHEME
+V
DD
VOLUME
CONTROL
OUT_
VOL
BIAS
GND
GND
HPOUT_
-V
DD
DirectDrive BIASING SCHEME
Figure 2. Traditional Headphone Amplifier Output Waveform
vs. DirectDrive Headphone Amplifier Output Waveform
Figure 1. MAX9750/MAX9751 Signal Path
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 no longer have a
Detailed Description
01/MAX975
The MAX9750/MAX9751/MAX9755 combine a 2.6W BTL
speaker amplifier and a 110mW DirectDrive headphone
amplifier with integrated headphone sensing and com-
prehensive click-and-pop suppression. The MAX9750
features an analog volume control, BEEP input, and
four-level gain control. The MAX9751 features a 2:1
input stereo multiplexer and two-level gain control. All
devices feature high 90dB PSRR, low 0.01% THD+N,
industry-leading click-pop performance, and a low-
power shutdown mode.
DC component (typically V
/ 2). This eliminates the
DD
large DC-blocking capacitors required with convention-
al headphone amplifiers, conserving board space and
system cost, and improving frequency response.
The MAX9750 features an analog volume control that
varies the gain of the amplifiers based on the DC volt-
age applied at VOL. Both devices feature an undervolt-
age lockout that prevents operation from an insufficient
power supply and click-and-pop suppression that elim-
inates audible transients on startup and shutdown. The
amplifiers include thermal-overload and short-circuit
protection, and can withstand 8kV ESD strikes on the
headphone amplifier outputs (IEC air discharge). An
additional feature of the speaker amplifiers is that there
is no phase inversion from input to output.
Each signal path consists of an input amplifier that sets
the gain of the signal path and feeds both the speaker
and headphone amplifier (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.
The headphone amplifiers use Maxim’s DirectDrive
architecture that eliminates the bulky output DC-block-
ing capacitors required by traditional headphone ampli-
fiers. A charge pump inverts the positive supply
DirectDrive
Conventional single-supply headphone amplifiers have
their outputs biased about a nominal DC voltage (typi-
cally half the supply) for maximum dynamic range.
Large coupling capacitors are needed to block this DC
bias from the headphones. Without these capacitors, a
(CPV ), creating a negative supply (CPV ). The
DD
SS
headphone amplifiers operate from these bipolar sup-
plies with their outputs biased about GND (Figure 2).
12 ______________________________________________________________________________________
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
01/MAX975
significant amount of DC current flows to the headphone,
resulting in unnecessary power dissipation and possible
damage to both headphone and headphone amplifier.
LOW-FREQUENCY ROLLOFF
(R = 16Ω)
L
0
Maxim’s DirectDrive architecture uses a charge pump to
an internal negative supply voltage. This allows the
MAX9750/MAX9751/MAX9755 headphone amplifier out-
put to be biased about GND, almost doubling the dynam-
ic 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 MAX9750/MAX9751/MAX9755 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 and Load
Resistance graph in the Typical Operating
Characteristics for details of the possible capacitor val-
ues.
-3
DirectDrive
330μF
220μF
-6
-9
-12
-15
-18
100μF
33μF
-21
-24
-27
-30
10
100
1k
FREQUENCY (Hz)
10k
100k
Figure 3. Low-Frequency Attenuation of Common DC-Blocking
Capacitor Values
Previous attempts to eliminate the output coupling
capacitors involved biasing the headphone return
(sleeve) to the DC bias voltage of the headphone
amplifiers. This method raised some issues:
the filter can attenuate low-frequency signals within
the audio band. Larger values of C
reduce the
OUT
attenuation but are physically larger, more expen-
sive capacitors. Figure 3 shows the relationship
1) The sleeve is typically grounded to the chassis. Using
this biasing approach, the sleeve must be isolated
from system ground, complicating product design.
between the size of C
and the resulting low-fre-
OUT
quency attenuation. Note that the -3dB point for a
16Ω headphone with a 100µF blocking capacitor is
100Hz, well within the audio band.
2) During an ESD strike, the amplifier’s ESD structures
are the only path to system ground. The amplifier
must be able to withstand the full ESD strike.
2) The voltage coefficient of the capacitor, the change
in capacitance due to a change in the voltage
across the capacitor, distorts the audio signal. At
frequencies around the -3dB point, the reactance of
the capacitor dominates, and the voltage coefficient
appears as frequency-dependent distortion. Figure
4 shows the THD+N introduced by two different
capacitor dielectrics. Note that around the -3dB
point, THD+N increases dramatically.
3) When using the headphone jack as a lineout to other
equipment, the bias voltage on the sleeve may con-
flict with the ground potential from other equipment,
resulting in large ground-loop current and possible
damage to the amplifiers.
Low-Frequency Response
In addition to the cost and size disadvantages, the DC-
blocking capacitors limit the low-frequency response of
the amplifier and distort the audio signal:
The combination of low-frequency attenuation and fre-
quency-dependent distortion compromises audio
reproduction. DirectDrive improves low-frequency
reproduction in portable audio equipment that empha-
sizes low-frequency effects such as multimedia lap-
tops, and MP3, CD, and DVD players.
1) The impedance of the headphone load to the DC-
blocking capacitor forms a highpass filter with the
-3dB point determined by:
1
f
=
−3dB
2πR C
L
OUT
Charge Pump
The MAX9750/MAX9751/MAX9755 feature a low-noise
charge pump. The 550kHz 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 transients. Limiting the switching speed of
the charge pump minimizes the di/dt noise caused by the
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 sin-
gle-ended, single-supply headphone amplifiers to
block the midrail DC component of the audio signal
from the headphones. Depending on the -3dB point,
______________________________________________________________________________________ 13
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
V
DD
ADDITIONAL THD+N DUE
TO DC-BLOCKING CAPACITORS
MAX9750/
MAX9751/
MAX9755
10
1
10μA
SHUTDOWN
CONTROL
20
14
HPS
0.1
HPOUTL
TANTALUM
13
0.01
0.001
0.0001
HPOUTR
1kΩ
1kΩ
ALUM/ELEC
10
100
1k
10k
100k
FREQUENCY (Hz)
Figure 4. Distortion Contributed by DC-Blocking Capacitors
Figure 5. HPS Configuration
parasitic bond wire and trace inductance. Although not
typically required, additional high-frequency ripple atten-
uation can be achieved by increasing the size of Cꢁ (see
the Block Diagrams).
Gain Selection
MAX9750
The MAX975± features an internally set, selectable gain.
The GAIN1 and GAINꢁ inputs set the maximum gain of
the MAX975± speaker and headphone amplifiers (Table
1). The gain of the device can vary based upon the volt-
age at VOL (see the Analog Volume Control (VOL) sec-
tion). However, the maximum gain cannot be exceeded.
Headphone Sense Input (HPS)
The headphone sense input (HPS) monitors the head-
phone jack and automatically configures the device
based upon the voltage applied at HPS. A voltage of
less than ±.8V sets the device to speaker mode. A volt-
age of greater than ꢁV disables the bridge amplifiers
and enables the headphone amplifiers.
01/MAX975
MAX9751/MAX9755
The gain of the MAX9751/MAX9755 is set by the GAIN
input. Driving GAIN high sets the gain of the speaker
amplifiers to 9dB and the gain of the headphone ampli-
fiers to ±dB. Driving GAIN low sets the gain of the
speaker amplifiers to 1±.5dB, and the gain of the head-
phone amplifiers to ꢀdB (Table ꢁ).
For automatic headphone detection, connect HPS to the
control pin of a ꢀ-wire headphone jack as shown in
Figure 5. With no headphone present, the output imped-
ance 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 HPS is pulled
Analog Volume Control (VOL)
The MAX975± features an analog volume control that
varies the gain of the device in ꢀ1 discrete steps based
upon the DC voltage applied to VOL. The input range of
to V
through a 1±µA current source.
DD
BIAS
The MAX975±/MAX9751/MAX9755 feature an internally
generated, power-supply independent, common-mode
bias voltage of 1.8V 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.
V
is from ± (full volume) to ±.858 x HPV
(full mute),
VOL
DD
with example step sizes shown in Table ꢀ. Connect the
reference of the device driving VOL (Figure 6) to HPV
Since the volume control ADC is ratiometric to HPV
.
,
DD
DD
any changes in HPV
are negated. The gain step sizes
DD
are not constant; the step sizes are ±.5dB/step at the
upper extreme, ꢁdB/step in the midrange, and 4dB/step
at the lower extreme. Figure 7 shows the transfer function
of the volume control for a ꢀ.ꢀV supply.
14 ______________________________________________________________________________________
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
01/MAX975
Table 1. MAX9750 Maximum Gain Settings
SPEAKER MODE GAIN (dB)
GAIN2
GAIN1
HEADPHONE MODE GAIN (dB)
MAX9750A
MAX9750B
MAX9750C
±
±
1
1
±
1
±
1
9
15
16.5
18
6
7.5
9
±
±
ꢀ
ꢀ
1±.5
1ꢁ
1ꢀ.5
19.5
1±.5
Table 2. MAX9751/MAX9755 Gain Settings
SPEAKER MODE
GAIN (dB)
HEADPHONE
MODE GAIN (dB)
GAIN
MAX9750
HPV
VOL
DD
±
1
1±.5
9
ꢀ
±
V
REF
DAC
BEEP Input
The MAX975± features an audible alert beep input
(BEEP) that accepts a mono system alert signal and
mixes it into the stereo audio path. When the amplitude
Figure 6. Volume Control Circuit
of V
exceeds 8±±mV
(Figure 8) and the
P-P
BEEP(OUT)
Input Multiplexer
frequency of the beep signal is greater than ꢀ±±Hz, the
beep signal is mixed into the active audio path (speaker
The MAX9751 features a ꢁ:1 input multiplexer on each
amplifier, allowing input selection between two stereo
sources. The logic input IN1/2 controls both multiplex-
ers. A logic high selects input IN_1 and a logic low
selects input IN_ꢁ.
or headphone). If the signal at V
is either
BEEP(OUT)
< 8±±mV
or < ꢀ±±Hz, 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 of V
times the gain of the selected signal path.
BEEP(OUT)
Shutdown
The MAX975±/MAX9751/MAX9755 features a ±.ꢁµA,
low-power shutdown mode that reduces quiescent cur-
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
The input resistor (R ) sets the gain of the BEEP input
B
amplifier, and thus the amplitude of V
. Choose
BEEP(OUT)
R based on:
B
V
× R
INT
±.ꢀ
IN
R
≤
B
GND. Connect SHDN to V
for normal operation.
DD
Click-and-Pop Suppression
where R
is the value of the BEEP amplifier feedback
INT
resistor (47kΩ) and V is the BEEP input amplitude.
IN
Speaker Amplifier
The MAX975±/MAX9751/MAX9755 speaker amplifiers
feature Maxim’s comprehensive, industry-leading click-
and-pop suppression. During startup, the click-pop
suppression circuitry eliminates any audible transient
sources internal to the device. When entering shut-
down, both amplifier outputs ramp to GND quickly and
simultaneously.
Note that the BEEP amplifier can be set up as either an
attenuator, if the original alert signal amplitude is too
large, or set to gain up the alert signal if it is below
8±±mV . 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 8).
______________________________________________________________________________________ 15
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Table 3A. MAX9750A Volume Levels
V
(V)
SPEAKER MODE GAIN (dB)
HEADPHONE MODE GAIN (dB)
VOL
GAIN1 = 0,
GAIN2 = 0
GAIN1 = 1,
GAIN2 = 0
GAIN1 = 0,
GAIN2 = 1
GAIN1 = 1
GAIN2 = 1
GAIN1 = X,
GAIN2 = 0
GAIN1 = X,
GAIN2 = 1
V
*
V
MAX
*
HPV
*
DD
MIN
±
±.49
±.±74
±.16±
±.18ꢀ
±.ꢁ±7
±.ꢁꢀ±
±.ꢁ5ꢀ
±.ꢁ77
±.ꢀ±±
±.ꢀꢁ4
±.ꢀ47
±.ꢀ71
±.ꢀ94
±.418
±.441
±.464
±.488
±.511
±.5ꢀ5
±.558
±.58ꢁ
±.6±5
±.6ꢁ8
±.65ꢁ
±.675
±.699
±.7ꢁꢁ
±.746
±.769
±.79ꢀ
±.816
±.8ꢀ9
±.858
9
8
1±.5
1±
1ꢁ
11.5
11
1ꢀ.5
1ꢀ
±
-1
ꢀ
ꢁ.5
ꢁ
±.49
±.567ꢀ
±.6447
±.7ꢁꢁ
±.567ꢀ
±.6447
±.7ꢁꢁ
7
9
1ꢁ.5
1ꢁ
-ꢁ
6
8
1±.5
1±
-ꢀ
1.5
1
±.7994
±.8767
±.9541
1.±ꢀ14
1.1±88
1.1861
1.ꢁ6ꢀ5
1.ꢀ4±8
1.418ꢁ
1.4955
1.57ꢁ8
1.65±ꢁ
1.7ꢁ75
1.8±49
1.88ꢁꢁ
1.9596
ꢁ.±ꢀ69
ꢁ.114ꢀ
ꢁ.1916
ꢁ.ꢁ69
4
7
11.5
11
-5
±.7994
±.8767
±.9541
1.±ꢀ14
1.1±88
1.1861
1.ꢁ6ꢀ5
1.ꢀ4±8
1.418ꢁ
1.4955
1.57ꢁ8
1.65±ꢁ
1.7ꢁ75
1.8±94
1.88ꢁꢁ
1.9596
ꢁ.±ꢀ69
ꢁ.114ꢀ
ꢁ.1916
ꢁ.ꢁ69
ꢁ
6
9
-7
±
±
4
8
1±.5
1±
-9
-1
-ꢁ
ꢁ
7
-11
-1ꢀ
-15
-17
-19
-ꢁ1
-ꢁꢀ
-ꢁ5
-ꢁ7
-ꢁ9
-ꢀ1
-ꢀꢀ
-ꢀ5
-ꢀ7
-ꢀ9
-41
-4ꢀ
-47
-51
-55
-59
-6ꢀ
-67
-71
MUTE
-ꢁ
-4
±
6
9
-ꢀ
-6
-ꢁ
4
8
-5
-8
-4
ꢁ
7
-7
-1±
-1ꢁ
-14
-16
-18
-ꢁ±
-ꢁꢁ
-ꢁ4
-ꢁ6
-ꢁ8
-ꢀ±
-ꢀꢁ
-ꢀ4
-ꢀ8
-4ꢁ
-46
-5±
-54
-58
-6ꢁ
MUTE
-6
±
6
-9
-8
-ꢁ
4
-11
-1ꢀ
-15
-17
-19
-ꢁ1
-ꢁꢀ
-ꢁ5
-ꢁ7
-ꢁ9
-ꢀ1
-ꢀꢀ
-ꢀ5
-ꢀ7
-ꢀ9
-41
-4ꢀ
-47
-51
MUTE
-1±
-1ꢁ
-14
-16
-18
-ꢁ±
-ꢁꢁ
-ꢁ4
-ꢁ6
-ꢁ8
-ꢀ±
-ꢀꢁ
-ꢀ4
-ꢀ8
-4ꢁ
-46
-5±
-54
MUTE
-4
ꢁ
-6
±
-8
-ꢁ
-1±
-1ꢁ
-14
-16
-18
-ꢁ±
-ꢁꢁ
-ꢁ4
-ꢁ6
-ꢁ8
-ꢀ±
-ꢀꢁ
-ꢀ4
-ꢀ8
-4ꢁ
MUTE
-4
-6
-8
01/MAX975
-1±
-1ꢁ
-14
-16
-18
-ꢁ±
-ꢁꢁ
-ꢁ4
-ꢁ6
-ꢁ8
-ꢀ±
-ꢀꢁ
MUTE
ꢁ.ꢀ46ꢀ
ꢁ.4ꢁꢀ7
ꢁ.5±1
ꢁ.ꢀ46ꢀ
ꢁ.4ꢁꢀ7
ꢁ.5±1
ꢁ.578ꢀ
ꢁ.6557
ꢁ.7ꢀꢀ
ꢁ.578ꢀ
ꢁ.6557
ꢁ.7ꢀꢀ
ꢁ.81±4
ꢀ.ꢀ
ꢁ.81±4
*Based on HPV = ꢀ.ꢀV
DD
X = Don’t care.
16 ______________________________________________________________________________________
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
01/MAX975
Table 3B. MAX9750B Volume Levels
HEADPHONE MODE GAIN
(dB)
V
(V)
SPEAKER MODE GAIN (dB)
VOL
GAIN1 = 0,
GAIN2 = 0
GAIN1 = 1,
GAIN2 = 0
GAIN1 = 0,
GAIN2 = 1
GAIN1 = 1
GAIN2 = 1
GAIN1 = X,
GAIN2 = 0
GAIN1 = X,
GAIN2 = 1
V
*
V
MAX
*
HPV
*
DD
MIN
±
±.49
±.±74
±.16±
±.18ꢀ
±.ꢁ±7
±.ꢁꢀ±
±.ꢁ5ꢀ
±.ꢁ77
±.ꢀ±±
±.ꢀꢁ4
±.ꢀ47
±.ꢀ71
±.ꢀ94
±.418
±.441
±.464
±.488
±.511
±.5ꢀ5
±.558
±.58ꢁ
±.6±5
±.6ꢁ8
±.65ꢁ
±.675
±.699
±.7ꢁꢁ
±.746
±.769
±.79ꢀ
±.816
±.8ꢀ9
±.858
15
14
16.5
16
18
17.5
17
19.5
19
±
-1
ꢀ
ꢁ.5
ꢁ
±.49
±.567ꢀ
±.6447
±.7ꢁꢁ
±.567ꢀ
±.6447
±.7ꢁꢁ
1ꢀ
15
18.5
18
-ꢁ
1ꢁ
14
16.5
16
-ꢀ
1.5
1
±.7994
±.8767
±.9541
1.±ꢀ14
1.1±88
1.1861
1.ꢁ6ꢀ5
1.ꢀ4±8
1.418ꢁ
1.4955
1.57ꢁ8
1.65±ꢁ
1.7ꢁ75
1.8±49
1.88ꢁꢁ
1.9596
ꢁ.±ꢀ69
ꢁ.114ꢀ
ꢁ.1916
ꢁ.ꢁ69
1±
1ꢀ
17.5
17
-5
±.7994
±.8767
±.9541
1.±ꢀ14
1.1±88
1.1861
1.ꢁ6ꢀ5
1.ꢀ4±8
1.418ꢁ
1.4955
1.57ꢁ8
1.65±ꢁ
1.7ꢁ75
1.8±49
1.88ꢁꢁ
1.9596
ꢁ.±ꢀ69
ꢁ.114ꢀ
ꢁ.1916
ꢁ.ꢁ69
8
1ꢁ
15
-7
±
6
1±
14
16.5
16
-9
-1
4
8
1ꢀ
-11
-1ꢀ
-15
-17
-19
-ꢁ1
-ꢁꢀ
-ꢁ5
-ꢁ7
-ꢁ9
-ꢀ1
-ꢀꢀ
-ꢀ5
-ꢀ7
-ꢀ9
-41
-4ꢀ
-47
-51
-55
-59
-6ꢀ
-67
-71
MUTE
-ꢁ
ꢁ
6
1ꢁ
15
-ꢀ
±
4
1±
14
-5
-ꢁ
ꢁ
8
1ꢀ
-7
-4
±
6
1ꢁ
-9
-6
-ꢁ
4
1±
-11
-1ꢀ
-15
-17
-19
-ꢁ1
-ꢁꢀ
-ꢁ5
-ꢁ7
-ꢁ9
-ꢀ1
-ꢀꢀ
-ꢀ5
-ꢀ7
-ꢀ9
-41
-4ꢀ
-47
-51
MUTE
-8
-4
ꢁ
8
-1±
-1ꢁ
-14
-16
-18
-ꢁ±
-ꢁꢁ
-ꢁ4
-ꢁ6
-ꢁ8
-ꢀꢁ
-ꢀ6
-4±
-44
-48
-5ꢁ
-56
MUTE
-6
±
6
-8
-ꢁ
4
-1±
-1ꢁ
-14
-16
-18
-ꢁ±
-ꢁꢁ
-ꢁ4
-ꢁ6
-ꢁ8
-ꢀꢁ
-ꢀ6
-4±
-44
-48
MUTE
-4
ꢁ
-6
±
-8
-ꢁ
-1±
-1ꢁ
-14
-16
-18
-ꢁ±
-ꢁꢁ
-ꢁ4
-ꢁ6
-ꢁ8
-ꢀꢁ
-ꢀ6
MUTE
-4
-6
-8
-1±
-1ꢁ
-14
-16
-18
-ꢁ±
-ꢁꢁ
-ꢁ4
-ꢁ6
MUTE
ꢁ.ꢀ46ꢀ
ꢁ.4ꢁꢀ7
ꢁ.5±1
ꢁ.ꢀ46ꢀ
ꢁ.4ꢁꢀ7
ꢁ.5±1
ꢁ.578ꢀ
ꢁ.6557
ꢁ.7ꢀꢀ
ꢁ.578ꢀ
ꢁ.6557
ꢁ.7ꢀꢀ
ꢁ.81±4
ꢀ.ꢀ
ꢁ.81±4
*Based on HPV = ꢀ.ꢀV
DD
X = Don’t care.
______________________________________________________________________________________ 17
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Table 3C. MAX9750C Volume Levels
V
(V)
SPEAKER MODE GAIN (dB)
HEADPHONE MODE GAIN (dB)
VOL
GAIN1 = 0,
GAIN2 = 0
GAIN1 = 1,
GAIN2 = 0
GAIN1 = 0,
GAIN2 = 1
GAIN1 = 1
GAIN2 = 1
GAIN1 = X,
GAIN2 = 0
GAIN1 = X,
GAIN2 = 1
V
*
V
*
HPV
*
DD
MIN
MAX
±
±.49
±.±74
±.16±
±.18ꢀ
±.ꢁ±7
±.ꢁꢀ±
±.ꢁ5ꢀ
±.ꢁ77
±.ꢀ±±
±.ꢀꢁ4
±.ꢀ47
±.ꢀ71
±.ꢀ94
±.418
±.441
±.464
±.488
±.511
±.5ꢀ5
±.558
±.58ꢁ
±.6±5
±.6ꢁ8
±.65ꢁ
±.675
±.699
±.7ꢁꢁ
±.746
±.769
±.79ꢀ
±.816
±.8ꢀ9
±.858
6
5
7.5
7
9
8.5
8
1±.5
1±
9.5
9
±
-1
ꢀ
ꢁ.5
ꢁ
±.49
±.567ꢀ
±.6447
±.7ꢁꢁ
±.567ꢀ
±.6447
±.7ꢁꢁ
4
6
-ꢁ
ꢀ
5
7.5
7
-ꢀ
1.5
1
±.7994
±.8767
±.9541
1.±ꢀ14
1.1±88
1.1861
1.ꢁ6ꢀ5
1.ꢀ4±8
1.418ꢁ
1.4955
1.57ꢁ8
1.65±ꢁ
1.7ꢁ75
1.8±49
1.88ꢁꢁ
1.9596
ꢁ.±ꢀ69
ꢁ.114ꢀ
ꢁ.1916
ꢁ.ꢁ69
1
4
8.5
8
-5
±.7994
±.8767
±.9541
1.±ꢀ14
1.1±88
1.1861
1.ꢁ6ꢀ5
1.ꢀ4±8
1.418ꢁ
1.4955
1.57ꢁ8
1.65±ꢁ
1.7ꢁ75
1.8±49
1.88ꢁꢁ
1.9596
ꢁ.±ꢀ69
ꢁ.114ꢀ
ꢁ.1916
ꢁ.ꢁ69
-1
ꢀ
6
-7
±
-ꢀ
1
5
7.5
7
-9
-1
-5
-1
4
-11
-1ꢀ
-15
-17
-19
-ꢁ1
-ꢁꢀ
-ꢁ5
-ꢁ7
-ꢁ9
-ꢀ1
-ꢀꢀ
-ꢀ5
-ꢀ7
-ꢀ9
-41
-4ꢀ
-47
-51
-55
-59
-6ꢀ
-67
-71
MUTE
-ꢁ
-7
-ꢀ
ꢀ
6
-ꢀ
-9
-5
1
5
-5
-11
-1ꢀ
-15
-17
-19
-ꢁ1
-ꢁꢀ
-ꢁ5
-ꢁ7
-ꢁ9
-ꢀ1
-ꢀꢀ
-ꢀ5
-ꢀ7
-41
-45
-48
-5ꢀ
-57
-61
-65
MUTE
-7
-1
4
-7
-9
-ꢀ
ꢀ
-9
-11
-1ꢀ
-15
-17
-19
-ꢁ1
-ꢁꢀ
-ꢁ5
-ꢁ7
-ꢁ9
-ꢀ1
-ꢀ
-5
1
-11
-1ꢀ
-15
-17
-19
-ꢁ1
-ꢁꢀ
-ꢁ5
-ꢁ7
-ꢁ9
-ꢀ1
-ꢀꢀ
-ꢀ5
-ꢀ7
-ꢀ9
-41
-4ꢀ
-47
-51
MUTE
-7
-1
-9
-ꢀ
-11
-1ꢀ
-15
-17
-9
-5
-7
-9
01/MAX975
-11
-1ꢀ
-15
-17
-19
-ꢁ1
-ꢁꢀ
-ꢁ5
-ꢁ7
-ꢁ9
-ꢀ1
-ꢀꢀ
-ꢀ5
MUTE
-ꢁ1
-ꢁꢀ
-ꢁ
-ꢁ7
-ꢁ9
-ꢀ1
-ꢀꢀ
-ꢀ5
-ꢀ7
-41
-45
MUTE
ꢁ.ꢀ46ꢀ
ꢁ.4ꢁꢀ7
ꢁ.5±1
-ꢀ5
-ꢀ7
-41
-45
-49
-5ꢀ
-57
MUTE
ꢁ.ꢀ46ꢀ
ꢁ.4ꢁꢀ7
ꢁ.5±1
ꢁ.578ꢀ
ꢁ.6557
ꢁ.7ꢀꢀ
ꢁ.578ꢀ
ꢁ.6557
ꢁ.7ꢀꢀ
ꢁ.81±4
ꢀ.ꢀ
ꢁ.81±4
*Based on HPV = ꢀ.ꢀV
DD
X = Don’t care.
18 ______________________________________________________________________________________
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
01/MAX975
MAX9750A
VOLUME CONTROL TRANSFER FUNCTION
MAX9750B
VOLUME CONTROL TRANSFER FUNCTION
20
10
20
10
GAIN1 = GAIN2 = 0
GAIN1 = GAIN2 = 0
0
0
SPEAKER MODE
SPEAKER MODE
AUDIO
-10
-20
-30
-40
-50
-60
-70
-80
-10
-20
-30
-40
-50
-60
-70
-80
AUDIO
TAPER POT
TAPER POT
HEADPHONE MODE
HEADPHONE MODE
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
(V)
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
(V)
V
VOL
V
VOL
Figure 7a. Volume Control Transfer Function
Figure 7b. Volume Control Transfer Function
Headphone Amplifier
MAX9750C
VOLUME CONTROL TRANSFER FUNCTION
In conventional single-supply headphone amplifiers,
the output-coupling capacitor is a major contributor of
audible clicks and pops. Upon startup, the amplifier
charges the coupling capacitor to its bias voltage, typi-
cally half the supply. Likewise, during shutdown, the
capacitor is discharged to GND. A DC shift across the
capacitor results, which in turn appears as an audible
transient at the speaker. Since the MAX975±/MAX9751/
MAX9755 do not require output-coupling capacitors, no
audible transient occurs.
20
GAIN1 = GAIN2 = 0
10
0
-10
SPEAKER MODE
-20
AUDIO
TAPER POT
-30
-40
-50
HEADPHONE MODE
-60
Additionally, the MAX975±/MAX9751/MAX9755 features
extensive click-and-pop suppression that eliminates
any audible transient sources internal to the device.
The Turn-On Response (Headphone Mode) and Turn-
Off Response (Headphone Mode) graphs in the Typical
Operating Characteristics shows that there are minimal
transient components in the audible range at the output
upon startup and shutdown.
-70
-80
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
(V)
V
VOL
Figure 7c. Volume Control Transfer Function
R
B1
0.47μF
0.47μF
0.47μF
47kΩ
R
INT
SOURCE 1
SOURCE 2
SOURCE 3
47kΩ
R
B2
47kΩ
SPEAKER/HEADPHONE
AMPLIFER INPUTS
BEEP
V
OUT(BEEP)
WINDOW
R
B3
47kΩ
DETECTOR
(0.8V THRESHOLD)
P-P
BIAS
FREQUENCY
DETECTOR
MAX9750
(300Hz THRESHOLD)
Figure 8. BEEP Input
______________________________________________________________________________________ 19
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
1000
V
DD
= 5V
R = 16Ω
L
100
10
A = 3dB
V
V
+1
-1
OUT(P-P)
OUTPUTS IN PHASE
1
2 x V
OUT(P-P)
0.1
V
OUT(P-P)
0.01
0.001
OUTPUTS 180° OUT OF PHASE
0
25
50
75
100
125
150
OUTPUT POWER (mW)
Figure 9. Bridge-Tied Load Configuration
Figure 1±. Total Harmonic Distortion Plus Noise vs. Output Power
with Inputs In/Out of Phase (Headphone Mode)
Power Dissipation and Heat Sinking
Under normal operating conditions, the MAX975±/
MAX9751/MAX9755 can dissipate a significant amount
of power. The maximum power dissipation for each
package is given in the Absolute Maximum Ratings
under Continuous Power Dissipation, or can be calcu-
lated by the following equation:
Applications Information
BTL Speaker Amplifiers
The MAX975±/MAX9751/MAX9755 feature speaker
amplifiers designed to drive a load differentially, a con-
figuration referred to as bridge-tied load (BTL). The BTL
configuration (Figure 9) offers advantages over the sin-
gle-ended configuration, where one side of the load is
connected to ground. Driving the load differentially
doubles the output voltage compared to a single-
ended amplifier under similar conditions. Thus, the
device’s differential gain is twice the closed-loop gain
of the input amplifier. The effective gain is given by:
T
− T
A
J(MAX)
P
=
DISSPKG(MAX)
01/MAX975
θ
JA
where T
is +15±°C, T is the ambient tempera-
A
J(MAX)
ture, and θ is the reciprocal of the derating factor in
JA
°C/W as specified in the Absolute Maximum Ratings
section. For example, θ of the thin QFN package is
JA
R
F
A
= ꢁ×
+4ꢁ°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).
VD
R
IN
Substituting ꢁ x V
into the following equation
OUT(P-P)
yields four times the output power due to double the
output voltage:
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
V
OUT(P−P)
V
=
=
RMS
maximum power dissipation for a given V
given by the following equation:
and load is
DD
ꢁ ꢁ
ꢁ
V
RMS
P
ꢁ
OUT
ꢁV
DD
R
P
=
L
DISS(MAX)
ꢁ
π R
Since the differential outputs are biased at midsupply,
there is no net DC voltage across the load. This elimi-
nates 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.
If the power dissipation for a given application exceeds
the maximum allowed for a given package, either reduce
DD
temperature, or add heatsinking to the device. Large
output, supply, and ground PC board traces improve the
maximum power dissipation in the package.
V
, increase load impedance, decrease the ambient
20 ______________________________________________________________________________________
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
01/MAX975
Table 4. Suggested Capacitor Manufacturers
SUPPLIER
Taiyo Yuden
TDK
PHONE
FAX
WEBSITE
8±±-ꢀ48-ꢁ496
8±7-8±ꢀ-61±±
847-9ꢁ5-±899
847-ꢀ9±-44±5
www.t-yuden.com
www.component.tdk.com
Thermal-overload protection limits total power dissipa-
tion in these devices. When the junction temperature
exceeds +16±°C, the thermal-protection circuitry dis-
ables the amplifier output stage. The amplifiers are
enabled once the junction temperature cools by 15°C.
This results in a pulsing output under continuous ther-
mal-overload conditions as the device heats and cools.
1
f
=
−ꢀdB
ꢁπR C
IN IN
R
is the amplifier’s internal input resistance value
IN
given in the Electrical Characteristics table. Choose C
IN
such that f
is well below the lowest frequency of
-ꢀdB
interest. Setting f
too high affects the amplifier’s
-ꢀdB
Output Power (Headphone Amplifier)
The headphone amplifiers have been specified for the
worst-case scenario—when both inputs are in phase.
Under this condition, the drivers simultaneously draw
current from the charge pump, leading to a slight loss in
low-frequency response. Use capacitors with low-volt-
age coefficient dielectrics, such as tantalum or alu-
minum electrolytic. Capacitors with high-voltage
coefficients, such as ceramics, may result in increased
distortion at low frequencies.
headroom of V . In typical stereo audio applications,
SS
BIAS Capacitor
the left and right signals have differences in both magni-
tude and phase, subsequently leading to an increase in
the maximum attainable output power. Figure 1± shows
the two extreme cases for in and out of phase. In reality,
the available power lies between these extremes.
BIAS is the output of the internally generated DC bias
voltage. The BIAS bypass capacitor, C
, improves
BIAS
PSRR and THD+N by reducing power supply and other
noise sources at the common-mode bias node, and
also generates the clickless/popless, startup/shutdown
DC bias waveforms for the speaker amplifiers. Bypass
BIAS with a 1µF capacitor to GND.
Power Supplies
The MAX975±/MAX9751/MAX9755 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-
Charge-Pump Capacitor Selection
Use capacitors with an ESR less than 1±±mΩ 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 4
lists suggested manufacturers.
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 ꢀV to 5.5V. V is the nega-
SS
tive supply of the headphone amplifiers. Connect V to
SS
DD
CPV . The charge pump is powered by CPV
.
SS
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
resistance to an extent. See the Output Power vs.
Charge-Pump Capacitance and Load Resistance
graph in the Typical Operating Characteristics. Above
ꢁ.ꢁµF, the on-resistance of the switches and the ESR of
C1 and Cꢁ dominate.
CPV
ranges from ꢀV 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
Component Selection
Input Filtering
The input capacitor (C ), in conjunction with the ampli-
IN
fier input resistance (R ), forms a highpass filter that
IN
removes the DC bias from an incoming signal (see the
Block Diagrams). The AC-coupling capacitor allows the
amplifier to bias the signal to an optimum DC level.
Assuming zero source impedance, the -ꢀdB point of
the highpass filter is given by:
Output Capacitor (C2)
The output capacitor value and ESR directly affect the
ripple at CPV . Increasing the value of Cꢁ reduces
SS
output ripple. Likewise, decreasing the ESR of Cꢁ
______________________________________________________________________________________ 21
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
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 and Load Resistance
graph in the Typical Operating Characteristics.
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.
Connect all components associated with the charge
pump (Cꢁ and Cꢀ) to the CPGND plane. Connect V
SS
CPV
Bypass Capacitor (C3)
DD
and CPV
together at the device. Place the charge-
SS
The CPV
bypass capacitor (Cꢀ) lowers the output
DD
pump capacitors (C1, Cꢁ, and Cꢀ) as close to the
device as possible. Bypass HPV and PV with a
impedance of the power supply and reduces the
impact of the MAX975±/MAX9751/MAX9755’s charge-
DD
DD
±.1µF capacitor to GND. Place the bypass capacitors
as close to the device as possible.
pump switching transients. Bypass CPV
with Cꢀ, the
DD
same value as C1, and place it physically close to
CPV and PGND (refer to the MAX975± Evaluation Kit
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.
For example, when compared to a ±Ω trace, a 1±±mΩ
trace reduces the power delivered to a 4Ω load from
ꢁ.1W to ꢁW. Large output, supply, and GND traces also
improve the power dissipation of the device.
DD
for a suggested layout).
Powering Other Circuits from a
Negative Supply
An additional benefit of the MAX975±/MAX9751/
MAX9755 is the internally generated negative supply volt-
age (CPV ). CPV
is used by the MAX975±/
SS
SS
MAX9751/MAX9755 to provide the negative supply for
the headphone amplifiers. It can also be used to power
The MAX975±/MAX9751/MAX9755 thin QFN package
features an exposed thermal pad on its underside. This
pad lowers the package’s thermal resistance by provid-
ing a direct heat conduction path from the die to the
printed circuit board. Connect the exposed thermal
pad to GND by using a large pad and multiple vias to a
GND plane on the bottom of the PCB.
other devices within a design. Current draw from CPV
SS
should be limited to 5mA, exceeding this affects the oper-
ation of the headphone amplifier. A typical application is
a negative supply to adjust the contrast of LCD modules.
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
01/MAX975
The charge-pump output impedance plot appears in
the Typical Operating Characteristics.
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 head 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
22 ______________________________________________________________________________________
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
01/MAX975
Simplified Block Diagrams (continued)
MUX
MAX9751
MAX9755
______________________________________________________________________________________ 23
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Block Diagrams
4.5V TO 5.5V
0.1μF
V
DD
25
6, 16
PV
DD
4.5V TO 5.5V
0.1μF
MAX9750
C
1μF
IN
4
5
OUTL+
OUTL-
GAIN/
VOLUME
CONTROL
1
INL
BTL
AMPLIFIER
LEFT-CHANNEL
AUDIO INPUT
C
1μF
IN
18
OUTR+
GAIN/
VOLUME
CONTROL
27
21
INR
BTL
AMPLIFIER
RIGHT-CHANNEL
AUDIO INPUT
17 OUTR-
BIAS
VOL
C
BIAS
15
20
HPV
HPS
DD
28
24
23
2
1μF
3V TO 5.5V
10μF
GAIN/
VOLUME
CONTROL
01/MAX975
GAIN1
GAIN2
BEEP
V
V
DD
HEADPHONE
DETECTION
14
13
DD
HPOUTL
R
B
1μF
47kΩ
BEEP
DETECTION
SHUTDOWN
CONTROL
22
SHDN
V
DD
HPOUTR
CPV
DD
7
3V TO 5.5V
C3
1μF
8
C1P
C1
1μF
CHARGE
PUMP
10
C1N
9
CPGND
26
3, 19
PGND
11 12
CPV
V
SS
GND
SS
C2
1μF
24 ______________________________________________________________________________________
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
01/MAX975
Block Diagrams (continued)
4.5V TO 5.5V
0.1μF
V
DD
25
6, 16
PV
DD
4.5V TO 5.5V
0.1μF
MAX9751
C
1μF
IN
1
2
INL1
INL2
4
5
OUTL+
OUTL-
LEFT CHANNEL
AUDIO INPUT
BTL
AMPLIFIER
C
INPUT
MUX
IN
1μF
LEFT CHANNEL
AUDIO INPUT
C
1μF
IN
27
INR1
INR2
BIAS
18
17
RIGHT CHANNEL
AUDIO INPUT
OUTR+
OUTR-
BTL
AMPLIFIER
INPUT
MUX
C
IN
28
21
1μF
RIGHT CHANNEL
AUDIO INPUT
C
1μF
BIAS
15
20
HPV
HPS
DD
3V TO 5.5V
10μF
MUX AND
GAIN
CONTROL
24
23
22
GAIN
IN1/2
SHDN
V
V
DD
14
13
HPOUTL
HEADPHONE
DETECTION
DD
V
DD
SHUTDOWN
CONTROL
HPOUTR
CPV
7
DD
3V TO 5.5V
C3
1μF
8
C1P
C1
1μF
CHARGE
PUMP
10
C1N
9
CPGND
11 12
26
3, 19
PGND
CV
SS
V
SS
GND
C2
1μF
LOGIC PINS CONFIGURED FOR:
GAIN = 1, 9dB SPEAKER GAIN/0dB HEADPHONE GAIN.
IN1/2 = 1, SELECTED INPUT LINE 1.
SHDN = 1, PART ACTIVE.
______________________________________________________________________________________ 25
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Block Diagrams (continued)
4.5V TO 5.5V
0.1μF
V
DD
25
6, 16 PV
DD
4.5V TO 5.5V
0.1μF
MAX9755
C
1μF
4
5
OUTL+
OUTL-
IN
INL
2
BTL
AMPLIFIER
LEFT CHANNEL
AUDIO INPUT
18
17
OUTR+
OUTR-
C
1μF
IN
28
21
INR
BTL
AMPLIFIER
RIGHT CHANNEL
AUDIO INPUT
BIAS
C
1μF
BIAS
HPV
DD
15
20
3V TO 5.5V
10μF
GAIN
CONTROL
01/MAX975
HPS
24
22
GAIN
V
V
DD
HEADPHONE
DETECTION
14
13
HPOUTL
SHDN
DD
SHUTDOWN
CONTROL
HPOUTR
CPV
DD
7
3V TO 5.5V
C3
1μF
8
C1P
C1
1μF
CHARGE
PUMP
10
C1N
9
CPGND
23, 26
GND
3, 19
PGND
11 12
CPV
V
SS
SS
C2
1μF
LOGIC PINS CONFIGURED FOR:
GAIN = 1, 9dB SPEAKER GAIN/0dB HEADPHONE GAIN.
SHDN = 1, PART ACTIVE.
26 ______________________________________________________________________________________
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
01/MAX975
System Diagrams
4.5V TO 5.5V 3V TO 5.5V
10μF
0.1μF
1μF
V
PV
DD
HPV
DD
DD
BIAS
OUTL+
OUTL-
MAX9750
1μF
1μF
1μF
1μF
OUTR+
OUTR-
AUX_IN
INL
OUT
CODEC
INR
HPOUTL
33kΩ
2kΩ
MAX4060
BEEP
BIAS
HPS
HPOUTR
2kΩ
SHDN
GAIN1
GAIN2
HPV
DD
μC
1μF
1μF
IN+
IN-
VOL
CPV
SS
3V TO 5.5V
CPV
DD
1μF
V
SS
1μF
C1P
1μF
CPGND
C1N
GND
PGND
______________________________________________________________________________________ 27
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
System Diagrams (continued)
4.5V TO 5.5V 3V TO 5.5V
10μF
0.1μF
V
PV
DD
HPV
DD
DD
1μF
OUTL+
OUTL-
INL1
INL2
CODEC
MAX9751
1μF
OUTR+
OUTR-
AUX_IN
1μF
INR1
INR2
OUT
2kΩ
HPOUTL
MAX4060
BIAS
HPS
SHDN
IN1/2
GAIN
CPV
HPOUTR
2kΩ
μC
1μF
1μF
IN+
IN-
CPV
SS
3V TO 5.5V
DD
1μF
V
SS
C1P
1μF
1μF
CPGND
BIAS
01/MAX975
C1N
GND
PGND
1μF
28 ______________________________________________________________________________________
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
01/MAX975
Pin Configurations
TOP VIEW
21 20
19 18
17 16
15
21 20
19 18
17 16
15
SHDN 22
IN1/2 23
GAIN 24
14 HPOUTL
13 HPOUTR
SHDN 22
GAIN2 23
GAIN1 24
14 HPOUTL
13 HPOUTR
12
V
SS
12
V
SS
MAX9751
MAX9750
V
25
11 CPV
10 C1N
V
25
11 CPV
10 C1N
DD
SS
DD
SS
GND 26
INR1 27
INR2 28
GND 26
INR 27
VOL 28
9
8
CPGND
C1P
9
8
CPGND
C1P
+
+
1
2
3
4
5
6
7
1
2
3
4
5
6
7
THIN QFN
THIN QFN
21 20
19 18
17 16
15
SHDN 22
GND 23
GAIN 24
14 HPOUTL
13 HPOUTR
12
V
SS
MAX9755
V
25
11 CPV
10 C1N
DD
SS
GND 26
N.C. 27
INR 28
9
8
CPGND
C1P
+
1
2
3
4
5
6
7
THIN QFN
Package Information
Chip Information
For the latest package outline information and land patterns, go
PROCESS: BiCMOS
to www.maxim-ic.com/packages.
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
ꢁ8 TQFN
Tꢁ855N-1
21-0140
______________________________________________________________________________________ 29
2.6W Stereo Audio Power Amplifiers and
DirectDrive Headphone Amplifiers
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
8
6/±8
Removed TSSOP package
1, ꢁ, 11, ꢁ±, ꢁ4, ꢁ5, ꢁ6, ꢁ9
01/MAX975
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.
30 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© ꢁ±±8 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
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