19-3882; Rev 1; 1/07
2.2W Stereo Audio Power Amplifier
with Analog Volume Control
Features
The MAX9787 combines a stereo, 2.2W audio power
amplifier with an analog volume control in a single device.
A high 90dB PSRR and low 0.01% THD+N ensures clean,
low-distortion amplification of the audio signal.
The analog volume control can be driven with a potentiometer, an RC-filtered PWM source, or a DAC output.
A BEEP input allows the addition of alert signals from
the controller to the audio path.
Industry-leading, click-and-pop suppression eliminates
audible transients during power and shutdown cycles.
Other features include single-supply voltage, a shutdown mode, logic-selectable gain, thermal-overload,
and output short-circuit protection.
♦ Class AB, 2.2W, Stereo BTL Speaker Amplifiers
The MAX9787 is offered in a space-saving, thermally
efficient, 28-pin thin QFN (5mm x 5mm x 0.8mm) package, and is specified over the extended -40°C to +85°C
temperature range.
♦ Space-Saving 28-Pin TQFN (5mm x 5mm x 0.8mm)
Applications
Ordering Information
Notebook PCs
Portable DVD Players
Flat-Panel TVs
LCD Projectors
Tablet PCs
Multimedia Monitors
PC Displays
♦ Analog Volume Control
♦ BEEP Input with Glitch Filter
♦ 5V Single-Supply Operation
♦ 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
PART
PIN-PACKAGE
MAX9787ETI+
28 TQFN-EP*
Pin Configuration
GND
PGND
OUTR+
OUTR-
PVDD
PVDD
20
19
18
17
16
15
SHDN
22
14
N.C.
GAIN2
23
13
N.C.
GAIN1
24
12
VSS
11
CPVSS
MAX9787
VDD
25
GND
26
10
C1N
INR
27
9
CPGND
VOL
28
8
C1P
*EXPOSED PAD.
3
4
5
6
7
OUTL-
PVDD
CPVDD
2
OUTL+
1
PGND
+
*EP
BEEP
MAX9787
VOLUME
21
INL
BEEP
BIAS
TOP VIEW
+5V
Σ
T2855N-1
Note: This device is specified for over -40°C to +85°C operating temperature range.
+Denotes lead-free package.
*EP = Exposed pad.
Typical Operating Circuit
Σ
PKG CODE
THIN QFN
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX9787
General Description
MAX9787
2.2W Stereo Audio Power Amplifier
with Analog Volume Control
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VDD, PVDD, CPVDD to GND) .......................+6V
GND to PGND.....................................................................±0.3V
CPVSS, C1N, VSS to GND .........................-6.0V to (GND + 0.3V)
Any Other Pin .............................................-0.3V to (VDD + 0.3V)
Duration of OUT_ Short Circuit to GND or PVDD ........Continuous
Duration of OUT_+ Short Circuit to OUT_- .................Continuous
Continuous Current (PVDD, OUT_, PGND) ...........................1.7A
Continuous Current (CPVDD, C1N, C1P, CPVSS, VSS)......850mA
Continuous Input Current (all other pins) .........................±20mA
Continuous Power Dissipation (TA = +70°C)
28-Pin Thin QFN (derate 23.8mW/°C above +70°C) .......1.9W
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
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V DD = PV DD = CPV DD = 5V, GND = PGND = CPGND = 0V, SHDN = V DD , C BIAS = 1µF, C1 = C2 = 1µF, speaker load
terminated between OUT_+ and OUT_-, GAIN1 = GAIN2 = VOL = 0V, TA = TMIN to TMAX, unless otherwise noted. Typical values are
at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
5.5
V
GENERAL
Supply Voltage Range
VDD, PVDD
Quiescent Supply Current
IDD
Shutdown Supply Current
ISHDN
Bias Voltage
VBIAS
Inferred from PSRR test
SHDN = GND
1.7
Switching Time
tSW
Gain or input switching
Input Resistance
RIN
Amplifier inputs (Note 2)
Turn-On Time
tSON
Output Offset Voltage
VOS
Power-Supply Rejection Ratio
(Note 3)
Output Power (Note 4)
Total Harmonic Distortion Plus
Noise
2
POUT
THD+N
14
29
mA
0.2
5
µA
1.8
1.9
V
30
kΩ
10
10
20
µs
25
Measured between OUT_+ and OUT_-,
TA = +25°C
PVDD or VDD = 4.5V to 5.5V (TA = +25°C)
PSRR
4.5
±0.4
75
80
f = 10kHz, VRIPPLE = 200mVP-P
55
RL = 8Ω
0.65
0.8
RL = 4Ω
1.2
1.5
RL = 3Ω
±6
mV
90
f = 1kHz, VRIPPLE = 200mVP-P
THD+N = 1%,
f = 1kHz,
TA = +25°C
ms
dB
W
2.2
RL = 8Ω, POUT = 500mW, f = 1kHz
0.01
RL = 4Ω, POUT = 1W, f = 1kHz
0.02
_______________________________________________________________________________________
%
2.2W Stereo Audio Power Amplifier
with Analog Volume Control
(V DD = PV DD = CPV DD = 5V, GND = PGND = CPGND = 0V, SHDN = V DD , C BIAS = 1µF, C1 = C2 = 1µF, speaker load
terminated between OUT_+ and OUT_-, GAIN1 = GAIN2 = VOL = 0V, TA = TMIN to TMAX, unless otherwise noted. Typical values are
at TA = +25°C.) (Note 1)
PARAMETER
Signal-to-Noise Ratio
SYMBOL
SNR
CONDITIONS
MIN
RL = 8Ω, POUT = 500mW, BW = 22Hz to
22kHz
TYP
MAX
UNITS
90
dB
Noise
Vn
BW = 22Hz to 22kHz, A-weighted
80
µVRMS
Capacitive-Load Drive
CL
No sustained oscillations
200
pF
Crosstalk
L to R, R to L, f = 10kHz
Slew Rate
SR
Gain (Maximum Volume Setting)
AVMAX(SPKR)
75
dB
1.4
V/µs
GAIN1 = 0, GAIN2 = 0
6
GAIN1 = 1, GAIN2 = 0
7.5
GAIN1 = 0, GAIN2 = 1
9
GAIN1 = 1, GAIN2 = 1
10.5
dB
CHARGE PUMP
Charge-Pump Frequency
fOSC
500
550
600
kHz
VOLUME CONTROL
VOL Input Impedance
RVOL
VOL Input Hysteresis
100
MΩ
10
mV
Full-Mute Input Voltage
(Note 5)
4.29
V
Channel Matching
AV = -25dB to +13.5dB
±0.2
dB
BEEP INPUT
Beep Signal Minimum Amplitude
VBEEP
Beep Signal Minimum Frequency
fBEEP
RB = 33kΩ (Note 6)
0.3
VP-P
300
Hz
LOGIC INPUT (SHDN, GAIN1, GAIN2, VOL)
Logic Input High Voltage
VIH
Logic Input Low Voltage
VIL
0.8
V
Logic Input Current
IIN
±1
µA
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
2
V
All devices are 100% production tested at room temperature. All temperature limits are guaranteed by design.
Guaranteed by design. Not production tested.
PSRR is specified with the amplifier input connected to GND through CIN.
Output power levels are measured with the thin QFN’s exposed paddle soldered to the ground plane.
See Table 3 for details of the mute levels.
The value of RB dictates the minimum beep signal amplitude (see the BEEP Input section).
_______________________________________________________________________________________
3
MAX9787
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(Measurement BW = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
0.01
OUTPUT POWER = 1.25W
0.01
0.001
0.0001
10k
0.0001
10
100k
100
1k
10k
100k
FREQUENCY (Hz)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
fIN = 10kHz
0.1
0.01
1
fIN = 10kHz
0.1
100
0.5
1.0
1.5
2.0
2.5
3.0
0
0.5
0.2
0.4
0.6
0.8
OUTPUT POWER (W)
5
MAX9787 toc07
2.0
THD+N = 10%
1.5
1.0
0
2.0
POWER DISSIPATION vs. OUTPUT POWER
POWER DISSIPATION (W)
OUTPUT POWER (W)
2.5
fIN = 1kHz
fIN = 20Hz
1.0
1.5
OUTPUT POWER (W)
OUTPUT POWER
vs. LOAD RESISTANCE
VCC = 5V
f = 1kHz
AV = 10.5dB
fIN = 10kHz
0.1
0.001
OUTPUT POWER (W)
3.0
1
fIN = 1kHz
0.001
0
THD+N = 1%
VDD = 5V
f = 1kHz
POUT = POUTL + POUTR
4
RL = 4Ω
3
2
RL = 8Ω
1
0.5
0
0
1
10
LOAD RESISTANCE (Ω)
100k
0.01
fIN = 20Hz
0.001
10k
VCC = 5V
RL = 8Ω
AV = 10.5dB
10
0.01
fIN = 1kHz
fIN = 20Hz
1k
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
THD+N (%)
1
100
FREQUENCY (Hz)
VCC = 5V
RL = 4Ω
AV = 10.5dB
10
THD+N (%)
VCC = 5V
RL = 3Ω
AV = 10.5dB
10
100
MAX9787 toc04
100
10
MAX9787 toc05
FREQUENCY (Hz)
MAX9787 toc08
0.0001
1k
0.01
OUTPUT POWER = 600mW
0.001
100
OUTPUT POWER = 100mW
0.1
OUTPUT POWER = 500mW
0.001
4
1
0.1
OUTPUT POWER = 500mW
10
VCC = 5V
RL = 8Ω
AV = 10.5dB
MAX9787 toc06
OUTPUT POWER = 1.5W
0.1
10
MAX9787 toc02
1
THD+N (%)
THD+N (%)
VCC = 5V
RL = 4Ω
AV = 10.5dB
THD+N (%)
VCC = 5V
RL = 3Ω
AV = 10.5dB
1
10
MAX9787 toc01
10
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX9787 toc03
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
THD+N (%)
MAX9787
2.2W Stereo Audio Power Amplifier
with Analog Volume Control
100
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
OUTPUT POWER (W)
_______________________________________________________________________________________
4.0
1.0
1.2
2.2W Stereo Audio Power Amplifier
with Analog Volume Control
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
VRIPPLE = 200mVP-P
AV = 10.5dB
OUTPUT REFERRED
-10
-20
-40
-50
-60
VCC = 5V
VRIPPLE = 200mVP-P
RL = 4Ω
-10
-20
-30
-40
-50
CROSSTALK (dB)
PSRR (dB)
-30
-60
-70
-80
-70
LEFT TO RIGHT
-90
-100
-110
-80
-90
-100
MAX9787 toc10
CROSSTALK vs. FREQUENCY
0
MAX9787 toc09
0
RIGHT TO LEFT
-120
100
10
1k
10k
100k
10
100
FREQUENCY (Hz)
1k
10k
100k
FREQUENCY (Hz)
TURN-ON RESPONSE
TURN-OFF RESPONSE
MAX9787 toc11
MAX9787 toc12
5V/div
5V/div
SHDN
SHDN
OUT_+
AND
OUT_-
2V/div
OUT_+
- OUT_-
100mV/div
OUT_+
AND
OUT_-
2V/div
OUT_+
- OUT_-
20mV/div
RL = 8Ω
RL = 8Ω
20ms/div
20ms/div
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
0.30
SUPPLY CURRENT (µA)
14
12
10
8
6
MAX9787 toc14
16
SUPPLY CURRENT (mA)
0.35
MAX9787 toc13
18
0.25
0.20
0.15
0.10
4
0.05
2
0
0
4.50
4.75
5.00
5.25
SUPPLY VOLTAGE (V)
5.50
4.50
4.75
5.00
5.25
5.50
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
5
MAX9787
Typical Operating Characteristics (continued)
(Measurement BW = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
2.2W Stereo Audio Power Amplifier
with Analog Volume Control
MAX9787
Pin Description
6
PIN
NAME
1
INL
Left-Channel Audio Input
FUNCTION
Audible Alert Beep Input
2
BEEP
3, 19
PGND
Power Ground
4
OUTL+
Left-Channel Positive Speaker Output
5
OUTL-
Left-Channel Negative Speaker Output
6, 15, 16
PVDD
Speaker Amplifier Power Supply
7
CPVDD
8
C1P
9
CPGND
10
C1N
11
CPVSS
12
VSS
Charge-Pump Power Supply
Charge-Pump Flying-Capacitor Positive Terminal
Charge-Pump Ground
Charge-Pump Flying-Capacitor Negative Terminal
Charge-Pump Output. Connect to VSS.
Amplifier Negative Power Supply
13, 14
N.C.
No Connection. Not internally connected.
17
OUTR-
Right-Channel Negative Speaker Output
18
OUTR+
Right-Channel Positive Speaker Output
20, 26
GND
Ground
21
BIAS
Common-Mode Bias Voltage. Bypass with a 1µF capacitor to GND.
22
SHDN
Shutdown. Drive SHDN low to disable the device. Connect SHDN to VDD for normal operation.
23
GAIN2
Gain Control Input 2
24
GAIN1
25
VDD
Power Supply
27
INR
Right-Channel Audio Input
28
VOL
EP
EP
Gain Control Input 1
Analog Volume Control Input
Exposed Pad. Connect to GND.
_______________________________________________________________________________________
2.2W Stereo Audio Power Amplifier
with Analog Volume Control
The MAX9787 combines a 2.2W bridge-tied load speaker amplifier and an analog volume control, BEEP input,
and four-level gain control. The MAX9787 features high
90dB, low 0.01% THD+N, industry-leading click-pop
performance, and a low-power shutdown mode.
Each signal path consists of an input amplifier that sets
the gain of the signal path, and feeds the speaker
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 180o out of phase.
An analog volume control varies the gain of the amplifiers based on the DC voltage applied at VOL. An undervoltage lockout prevents operation from an insufficient
power supply. Click-and-pop suppression eliminates
audible transients on startup and shutdown. The amplifiers include thermal-overload and short-circuit protection. An additional feature of the speaker amplifiers is
that there is no phase inversion from input to output.
Charge Pump
The MAX9787 features 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 parasitic
bond wire and trace inductance. Although not typically
IN_
required, additional high-frequency ripple attenuation
can be achieved by increasing the size of C2 (see the
Typical Operating Circuit).
BIAS
The MAX9787 features an internally generated, powersupply 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 performance of the device.
Gain Selection
The GAIN1 and GAIN2 inputs set the maximum gain of
the speaker and amplifiers (Table 1). The gain of the
device can vary based upon the voltage at VOL (see
the Analog Volume Control (VOL) section). However,
the maximum gain cannot be exceeded.
Analog Volume Control (VOL)
An analog volume control varies the gain of the device
in 31 discrete steps based upon the DC voltage
applied to VOL. The input range of VVOL is from 0 (full
volume) to 0.858 x PVDD (full mute), with example step
sizes shown in Table 2. Connect the reference of the
device driving VOL (Figure 2) to PVDD. Since the volume control ADC is ratiometric to PVDD, any changes in
Table 1. Gain Settings
GAIN2
GAIN1
SPEAKER MODE
GAIN (dB)
0
0
6
0
1
7.5
1
0
9
1
1
10.5
OUT_+
BIAS
BIAS
MAX9787
PVDD
VOL
VOLUME
CONTROL
OUT_
BIAS
Figure 1. MAX9787 Signal Path
VREF
DAC
VOL
Figure 2. Volume Control Circuit
_______________________________________________________________________________________
7
MAX9787
Detailed Description
MAX9787
2.2W Stereo Audio Power Amplifier
with Analog Volume Control
Table 2. Volume Levels
VVOL (V)
SPEAKER MODE GAIN (dB)
VMIN*
VTYP*
VMAX*
GAIN1 = 0,
GAIN2 = 0
GAIN1 = 1,
GAIN2 = 0
GAIN1 = 0,
GAIN2 = 1
GAIN1 = 1,
GAIN2 = 1
10.5
0
0.370
0.742
6
7.5
9
0.742
0.800
0.860
5
7
8.5
10
0.860
0.915
0.977
4
6
8
9.5
0.977
1.035
1.094
3
5
7.5
9
1.094
1.150
1.211
1
4
7
8.5
1.211
1.265
1.328
-1
3
6
8
1.328
1.385
1.446
-3
1
5
7.5
1.446
1.500
1.563
-5
-1
4
7
1.563
1.620
1.680
-7
-3
3
6
1.680
1.735
1.797
-9
-5
1
5
1.797
1.855
1.914
-11
-7
-1
4
1.914
1.970
2.032
-13
-9
-3
3
2.032
2.090
2.149
-15
-11
-5
1
2.149
2.205
2.266
-17
-13
-7
-1
2.266
2.320
2.383
-19
-15
-9
-3
2.383
2.440
2.500
-21
-17
-11
-5
2.500
2.555
2.617
-23
-19
-13
-7
2.617
2.675
2.735
-25
-21
-15
-9
2.735
2.790
2.852
-27
-23
-17
-11
2.852
2.910
2.969
-29
-25
-9
-13
2.969
3.025
3.086
-31
-27
-21
-15
3.086
3.140
3.203
-33
-29
-23
-17
3.203
3.260
3.321
-35
-31
-2
-19
3.321
3.375
3.438
-37
-3
-27
-21
3.438
3.495
3.555
-41
-35
-29
-23
3.555
3.610
3.672
-45
-37
-31
-25
3.672
3.730
3.789
-48
-41
-33
-27
3.789
3.845
3.907
-53
-45
-35
-29
3.907
3.965
4.024
-57
-49
-37
-31
4.024
4.080
4.141
-61
-53
-41
-33
4.141
4.195
4.258
-65
-57
-45
-35
4.258
4.290
5.000
MUTE
MUTE
MUTE
MUTE
*Based on PVDD = 5V
8
_______________________________________________________________________________________
2.2W Stereo Audio Power Amplifier
with Analog Volume Control
roughly the amplitude of VBEEP(OUT) times the gain of
the selected signal path.
The input resistor (RB) sets the gain of the BEEP input
amplifier, and thus the amplitude of V BEEP(OUT) .
Choose RB based on:
BEEP Input
An audible alert beep input (BEEP) accepts a mono
system alert signal and mixes it into the stereo audio
path. When the amplitude of V BEEP(OUT) exceeds
800mVP-P (Figure 4) and the frequency of the beep signal is greater than 400Hz, the beep signal is mixed into
the active audio path (speaker or headphone). If the
signal at VBEEP(OUT) is either < 800mVP-P or
