19-2387; Rev 1; 10/02
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
Features
♦ 1.4W into 8Ω Load (MAX4364)
♦ 1W into 8Ω Load (MAX4365)
♦ 0.04% THD + N at 1kHz
♦ 68dB PSRR at 217Hz
♦ 2.7V to 5.5V Single-Supply Operation
♦ 5mA Supply Current
♦ Low-Power, 10nA Shutdown Mode
♦ Pin Compatible with the LM4861/LM4862/LM4864
(MAX4364)
♦ Clickless Power-Up and Shutdown
♦ Thermal-Overload and Short-Circuit Protection
♦ Available in Thin QFN, µMAX, and SO Packages
The MAX4364 is available in a small 8-pin SO package.
The MAX4365 is available in tiny 8-pin thin QFN
(3mm ✕ 3mm ✕ 0.8mm) and µMAX packages.
Ordering Information
Applications
PART
TEMP RANGE
PIN-PACKAGE
Cellular Phones
MAX4364ESA
-40°C to +85°C
8 SO
PDAs
MAX4365EUA
-40°C to +85°C
8 µMAX
Two-Way Radios
MAX4365ETA
-40°C to +85°C
8 Thin QFN-EP*
TOP
MARK
—
—
ACD
*EP = Exposed paddle.
General-Purpose Audio
Pin Configurations appear at end of data sheet.
Typical Application Circuit/Functional Diagram
VCC
6
VCC
50kΩ
CLICKLESS/POPLESS
SHUTDOWN CONTROL
SHDN 1
2 BIAS
OUT- 8
CBIAS
50kΩ
3 IN+
CIN
AUDIO
INPUT
10kΩ
10kΩ
OUT+ 5
RIN
4 IN-
MAX4364
GND
7
RF
________________________________________________________________ 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
MAX4364/MAX4365
General Description
The MAX4364/MAX4365 are bridged audio power
amplifiers intended for portable audio devices with
internal speakers. The MAX4364 is capable of delivering 1.4W from a single 5V supply and 500mW from a
single 3V supply into an 8Ω load. The MAX4365 is
capable of delivering 1W from a single 5V supply and
450mW from a single 3V supply into an 8Ω load. The
MAX4364/MAX4365 feature 0.04% THD + N at 1kHz,
68dB PSRR at 217Hz and only 10nA of supply current
in shutdown mode.
The MAX4364/MAX4365 bridged outputs eliminate the
need for output-coupling capacitors, minimizing external component count. The MAX4364/MAX4365 also
include internal DC bias generation, clickless operation,
short-circuit and thermal-overload protection. Both
devices are unity-gain stable, with the gain set by two
external resistors.
MAX4364/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
ABSOLUTE MAXIMUM RATINGS
VCC, OUT_ to GND...................................................-0.3V to +6V
IN+, IN-, BIAS, SHDN to GND....................-0.3V to (VCC + 0.3V)
Output Short Circuit (OUT+ to OUT-) (Note 1)...........Continuous
Continuous Power Dissipation (TA = +70°C)
8-Pin µMAX (derate 4.1mW/°C above +70°C) ..............330mW
8-Pin Thin QFN (derate 24.4mW/°C above +70°C) ....1951mW
8-Pin SO (derate 5.88mW/°C above +70°C).................471mW
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
Note 1: Continuous power dissipation must also be observed.
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—5V
(VCC = 5V, RL = ∞, CBIAS = 1µF to GND, SHDN = GND, TA = +25°C, unless otherwise noted.) (Note 2)
PARAMETER
Supply Voltage Range
SYMBOL
VCC
CONDITIONS
Inferred from PSRR test
MIN
MAX4364
Supply Current
ICC
(Note 3)
TYP
2.7
7
MAX4364, TA = TMIN to TMAX
ISHDN
UNITS
5.5
V
13
17
MAX4365
5
MAX4365, TA = TMIN to TMAX
Shutdown Supply Current
MAX
8
11
SHDN = VCC
0.01
4
V
SHDN Threshold
VCC x
0.3
VIL
Output Offset Voltage
Power-Supply Rejection Ratio
Output Power
Total Harmonic Distortion Plus
Noise
VBIAS
VOS
PSRR
POUT
THD + N
Noise
Short-Circuit Current
µA
VCC x
0.7
VIH
Common-Mode Bias Voltage
mA
ISC
Thermal Shutdown Threshold
VCC/2 5%
(Note 4)
IN- = OUT+, IN+ = BIAS (Note 5)
VCC/2
+ 5%
V
±1
±10
mV
VCC = 2.7V to 5.5V
DC
VRIPPLE = 200mVP-P,
RL = 8Ω
217Hz
68
1kHz
58
RL = 8Ω, THD + N = 1%,
fIN = 1kHz (Note 6)
AV = -2V/V, RL = 8Ω,
fIN = 1kHz (Notes 7, 8)
55
VCC/2
75
MAX4364
1200
1400
MAX4365
800
1000
dB
mW
MAX4364,
POUT = 1W
0.04
MAX4365,
POUT = 750mW
0.1
%
fIN = 10kHz, BW = 22Hz to 22kHz
12
µVRMS
OUT+ to OUT- (Note 9)
600
mA
160
o
C
C
15
o
Power-Up Time
tPU
50
ms
Shutdown Time
tSHDN
10
µs
tENABLE
50
ms
Thermal Shutdown Hysteresis
Enable Time from Shutdown
2
_______________________________________________________________________________________
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
(VCC = 3V, RL = ∞, CBIAS = 1µF to GND, SHDN = GND, TA = +25°C, unless otherwise noted.) (Note 2)
PARAMETER
SYMBOL
Supply Current
ICC
CONDITIONS
(Note 3)
Shutdown Supply Current
ISHDN
SHDN = VCC
Output Power
POUT
RL = 8Ω, THD + N =
1%, fIN = 1kHz
(Note 6)
Total Harmonic Distortion Plus
Noise
THD + N
MIN
TYP
MAX4364
6
MAX4365
4.5
MAX
UNITS
mA
10
MAX4364
400
500
MAX4365
350
450
nA
mW
MAX4364,
POUT = 400mW
AV = -2V/V, RL = 8Ω,
fIN = 1kHz (Notes 7, 8) MAX4365,
POUT = 400mW
0.05
%
0.08
Note 2: All specifications are 100% tested at TA = +25°C.
Note 3: Quiescent power-supply current is specified and tested with no load on the outputs. Quiescent power-supply current
depends on the offset voltage when a practical load is connected to the amplifier.
Note 4: Common-mode bias voltage is the voltage on BIAS and is nominally VCC/2.
Note 5: Maximum differential-output offset voltage is tested in a unity-gain configuration. VOS = VOUT+ - VOUT-.
Note 6: Output power is specified by a combination of a functional output-current test, and characterization analysis.
Note 7: Guaranteed by design, not production tested.
Note 8: Measurement bandwidth for THD + N is 22Hz to 22kHz.
Note 9: Extended short-circuit conditions result in a pulsed output.
Typical Operating Characteristics
(VCC = 5V, THD + N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
VCC = 5V
AV = 4V/V
RL = 8Ω
1
0.25W
0.1
0.25W
100
0.25W
1W
0.5W
0.5W
1W
1W
0
1
0.1
0.5W
0.01
VCC = 5V
AV = 20V/V
RL = 8Ω
THD + N (%)
THD + N (%)
1
10
MAX4364 toc02
VCC = 5V
AV = 2V/V
RL = 8Ω
THD + N (%)
10
MAX4364 toc01
10
0.1
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364 toc03
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
0.01
0.01
1k
FREQUENCY (Hz)
10k
0
100
1k
FREQUENCY (Hz)
10k
0
100
1k
10k
FREQUENCY (Hz)
_______________________________________________________________________________________
3
MAX4364/MAX4365
ELECTRICAL CHARACTERISTICS—3V
Typical Operating Characteristics (continued)
(VCC = 5V, THD + N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
VCC = 3V
AV = 4V/V
RL = 8Ω
THD + N (%)
1
0.4W
0.1
10
1
VCC = 3V
AV = 20V/V
RL = 8Ω
THD + N (%)
VCC = 3V
AV = 2V/V
RL = 8Ω
MAX4364 toc05
10
MAX4364 toc04
10
THD + N (%)
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
0.25W
0.1
MAX4364 toc06
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
1
0.25W
0.1
0.4W
0.25W
0.4W
0
100
1k
10k
1k
0
10k
100
10k
1k
FREQUENCY (Hz)
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
20Hz
0.1
20Hz
0.1
1kHz
0.01
20kHz
1
1kHz
0.01
0.001
200
520
1000
1650
2450
MAX4364 toc09
1
20kHz
0.1
1kHz
0.01
0.001
0 40
VCC = 3V
AV = 2V/V
RL = 8Ω
10
THD + N (%)
20kHz
VCC = 5V
AV = 4V/V
RL = 8Ω
10
100
MAX4364 toc08
100
MAX4364 toc07
VCC = 5V
AV = 2V/V
RL = 8Ω
THD + N (%)
20Hz
0.001
0 40
200
520
1000
1650
0 20
2450
190
525
1000
1700
2500
OUTPUT POWER (mW)
OUTPUT POWER (mW)
OUTPUT POWER (mW)
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX4364
OUTPUT POWER vs. SUPPLY VOLTAGE
MAX4364
OUTPUT POWER vs. LOAD RESISTANCE
0.1
1kHz
0.01
10% THD + N
1500
1000
500
20Hz
3000
VCC = 5V
fIN = 1kHz
2400
OUTPUT POWER (mW)
20kHz
RL = 8Ω
fIN = 1kHz
2000
OUTPUT POWER (mW)
VCC = 3V
AV = 4V/V
RL = 8Ω
1
2500
MAX4364 toc10
100
MAX4364 toc11
THD + N (%)
100
FREQUENCY (Hz)
1
10
0
FREQUENCY (Hz)
100
10
0.01
0.01
MAX4364 toc12
0.01
THD + N (%)
MAX4364/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
1800
10% THD + N
1200
600
1% THD + N
1% THD + N
0
0.001
0 40
200
520
1000
OUTPUT POWER (mW)
4
1650
2440
0
2.7
3.4
4.1
SUPPLY VOLTAGE (V)
4.8
5.5
0
10
20
30
LOAD RESISTANCE (Ω)
_______________________________________________________________________________________
40
50
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
10% THD + N
400
1% THD + N
420
350
280
210
VCC = 5V
fIN = 1kHz
RL = 8Ω
10
20
40
30
50
MAX4364 toc15
240
210
180
150
120
90
VCC = 3V
fIN = 1kHz
RL = 8Ω
60
30
0
0
0
0
300
600
1200
900
1500
0
100
200
400
300
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
OUTPUT POWER (mW)
MAX4364
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX4364
SUPPLY CURRENT vs. TEMPERATURE
MAX4364
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
8.0
7.5
7.0
8
7
6
6.5
6.0
3.4
4.1
4.8
5.5
8
6
4
2
0
5
-40
-15
10
60
35
2.7
85
3.4
4.1
4.8
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
MAX4364
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
10
VCC = 5V
THD + N (%)
80
VCC = 5V
AV = 2V/V
RL = 8Ω
60
40
1
0.25W
0.5W
0.1
5.5
10
VCC = 5V
AV = 4V/V
RL = 8Ω
THD + N (%)
MAX4364 toc19
100
MAX4364 toc20
2.7
MAX4364 toc18
10
SUPPLY CURRENT (nA)
9
SUPPLY CURRENT (mA)
8.5
VCC = 5V
500
12
MAX4364 toc17
10
MAX4364 toc16
9.0
SUPPLY CURRENT (mA)
490
70
0
SUPPLY CURRENT (nA)
560
140
200
300
270
POWER DISSIPATION (mW)
800
600
630
POWER DISSIPATION (mW)
OUTPUT POWER (mW)
1000
700
MAX4364
POWER DISSIPATION vs. OUTPUT POWER
MAX4364 toc14
VCC = 3V
fIN = 1kHz
MAX4364 toc13
1200
MAX4364
POWER DISSIPATION vs. OUTPUT POWER
MAX4364 toc21
MAX4364
OUTPUT POWER vs. LOAD RESISTANCE
1
0.25W
0.5W
0.1
0.75W
0.75W
20
0.01
0
-40
-15
10
35
TEMPERATURE (°C)
60
85
0.01
0
100
1k
FREQUENCY (Hz)
10k
0
100
1k
10k
FREQUENCY (Hz)
_______________________________________________________________________________________
5
MAX4364/MAX4365
Typical Operating Characteristics (continued)
(VCC = 5V, THD + N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(VCC = 5V, THD + N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
0.25W
0.5W
0.75W
0.1
10
MAX4364 toc23
VCC = 3V
AV = 2V/V
RL = 8Ω
1
VCC = 3V
AV = 4V/V
RL = 8Ω
THD + N (%)
1
10
THD + N (%)
0.25W
0.1
1
0.4W
0.1
0.4W
0.01
0.01
0
100
1k
10k
0.01
0
100
1k
10k
0
100
FREQUENCY (Hz)
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
VCC = 5V
AV = 2V/V
RL = 8Ω
10
100
MAX4364 toc26
MAX4364 toc25
100
VCC = 5V
AV = 4V/V
RL = 8Ω
10
20kHz
THD + N (%)
0.25W
0.4W
1
THD + N (%)
20kHz
0.1
20Hz
0.1
20Hz
1
0.1
1kHz
1kHz
0.01
0.01
100
1k
10k
0.001
0
200 300 500 700 1000 1300 1600 2000 2400
500
750
1000
1300
1600
2000 2400
OUTPUT POWER (mW)
OUTPUT POWER (mW)
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX4365
OUTPUT POWER vs. SUPPLY VOLTAGE
20kHz
0.1
1kHz
1
VCC = 3V
AV = 4V/V
RL = 8Ω
20kHz
20Hz
0.1
0.01
1kHz
RL = 8Ω
fIN = 1kHz
2000
OUTPUT POWER (mW)
20Hz
THD + N (%)
1
10
2500
MAX4364 toc29
100
MAX4364 toc28
VCC = 3V
AV = 2V/V
RL = 8Ω
MAX4364 toc30
FREQUENCY (Hz)
100
0.01
0.01
0.001
0
10
10k
FREQUENCY (Hz)
VCC = 3V
AV = 20V/V
RL = 8Ω
1
1k
FREQUENCY (Hz)
10
THD + N (%)
0.25W
MAX4364 toc27
THD + N (%)
VCC = 5V
AV = 20V/V
RL = 8Ω
MAX4364 toc22
10
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364 toc24
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
THD + N (%)
MAX4364/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
10% THD + N
1500
1000
500
1% THD + N
0.001
0.001
6
0
0 125 200 250 325 400 500 600 725 800 1000
0 125 200 250 325 400 500 600 725 850 1000
OUTPUT POWER (mW)
OUTPUT POWER (mW)
2.7
3.4
4.1
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
4.8
5.5
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
800
600
400
800
800
600
10% THD + N
400
200
200
0
0
MAX4364 toc33
VCC = 3V
fIN = 1kHz
1000
OUTPUT POWER (mW)
OUTPUT POWER (mW)
1000
1200
MAX4365
POWER DISSIPATION vs. OUTPUT POWER
POWER DISSIPATION (mW)
VCC = 5V
fIN = 1kHz
MAX4364 toc31
1200
MAX4365
OUTPUT POWER vs. LOAD RESISTANCE
MAX4364 toc32
MAX4365
OUTPUT POWER vs. LOAD RESISTANCE
600
400
200
VCC = 5V
RL = 8Ω
fIN = 1kHz
1% THD + N
0
10
20
30
40
50
10
20
40
30
300
0
50
600
900
1200
1500
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
MAX4365
POWER DISSIPATION vs. OUTPUT POWER
MAX4365
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX4365
SUPPLY CURRENT vs. TEMPERATURE
150
100
VCC = 3V
RL = 8Ω
fIN = 1kHz
50
0
6
SUPPLY CURRENT (mA)
SUPPLY CURRENT (mA)
200
7
MAX4364 toc35
MAX4364 toc34
7
5
4
3
300
400
500
VCC = 5V
6
5
4
3
2.7
OUTPUT POWER (mW)
3.4
4.8
4.1
5.5
-40
-15
SUPPLY VOLTAGE (V)
80
VCC = 5V
70
SUPPLY CURRENT (nA)
10
35
60
85
MAX4365
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX4365
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
12
10
TEMPERATURE (°C)
8
6
4
MAX4364 toc38
200
MAX4364 toc37
100
SUPPLY CURRENT (nA)
0
MAX4364 toc36
LOAD RESISTANCE (Ω)
250
POWER DISSIPATION (mW)
0
0
60
50
40
30
20
2
10
0
0
2.7
3.4
4.1
SUPPLY VOLTAGE (V)
4.8
5.5
-40
-15
10
35
60
85
TEMPERATURE (°C)
_______________________________________________________________________________________
7
MAX4364/MAX4365
Typical Operating Characteristics (continued)
(VCC = 5V, THD + N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(VCC = 5V, THD + N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
-20
MAX4364 toc39
80
60
40
20
0
-20
-40
-60
-80
-100
-120
-140
-160
-180
MAX4364 toc40
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
GAIN AND PHASE vs. FREQUENCY
RL = 8Ω
VRIPPLE = 200mVP-P
-30
-40
PSRR (dB)
GAIN/PHASE (dB/DEGREES)
MAX4364/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
-50
-60
-70
AV = 1000V/V
-80
10
100
1k
10k
100k
1M
10M
10
100
FREQUENCY (Hz)
1k
10k
100k
FREQUENCY (Hz)
Pin Description
PIN
8
NAME
FUNCTION
MAX4364
MAX4365
SO
µMAX/QFN
1
7
SHDN
Active-High Shutdown. Connect SHDN to GND for normal operation.
2
1
BIAS
DC Bias Bypass. See BIAS Capacitor section for capacitor selection. Connect
CBIAS capacitor from BIAS to GND.
3
2
IN+
Noninverting Input
4
4
IN-
Inverting Input
5
5
OUT+
6
6
VCC
Power Supply
7
3
GND
Ground
8
8
OUT-
Bridged Amplifier Negative Output
Bridged Amplifier Positive Output
_______________________________________________________________________________________
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
BIAS
The MAX4364/MAX4365 feature an internally generated
common-mode bias voltage of VCC/2 referenced to
GND. BIAS provides both click-and-pop suppression
and the DC bias level for the audio signal. BIAS is internally connected to the noninverting input of one amplifier, and should be connected to the noninverting input
of the other amplifier for proper signal biasing (see
Typical Application Circuit/Functional Diagram).
Choose the value of the bypass capacitor as described
in the BIAS Capacitor section.
VOUT(P-P)
+1
2 x VOUT(P-P)
VOUT(P-P)
-1
Figure 1. Bridge-Tied Load Configuration
the device is twice the closed-loop gain of the input
amplifier. The effective gain is given by:
A VD = 2 ×
Substituting 2 ✕ VOUT(P-P) into the following equations
yields four times the output power due to doubling of
the output voltage.
VRMS =
VOUT(P−P)
Shutdown
The MAX4364/MAX4365 feature a 10nA, low-power
shutdown mode that reduces quiescent current consumption. Pulling SHDN high disables the device’s bias
circuitry, the amplifier outputs go high impedance, and
BIAS is driven to GND. Connect SHDN to GND for normal operation.
Current Limit
The MAX4364/MAX4365 feature a current limit that protects the device during output short circuit and overload conditions. When both amplifier outputs are
shorted to either VCC or GND, the short-circuit protection is enabled and the amplifier enters a pulsing mode,
reducing the average output current to a safe level. The
amplifier remains in this mode until the overload or
short-circuit condition is removed.
Applications Information
Bridge-Tied Load
The MAX4364/MAX4365 are designed to drive a load
differentially in a BTL configuration. The BTL configuration (Figure 1) offers advantages over the single-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 differential gain of
RF
RIN
2 2
2
V
POUT = RMS
RL
Since the differential outputs are biased at midsupply,
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, expensive, consume board space, and degrade
low-frequency performance.
Power Dissipation
Under normal operating conditions, the MAX4364/
MAX4365 can dissipate a significant amount of power.
The maximum power dissipation for each package is
given in the Absolute Maximum Ratings section under
Continuous Power Dissipation or can be calculated by
the following equation:
PDISSPKG(MAX ) =
TJ(MAX ) − TA
θJA
where TJ(MAX) is +150°C, TA is the ambient temperature and θJA is the reciprocal of the derating factor in
°C/W as specified in the Absolute Maximum Ratings
section. For example, θ JA of the µMAX package is
222°C/W.
_______________________________________________________________________________________
9
MAX4364/MAX4365
Detailed Description
The MAX4364/MAX4365 bridged audio power amplifiers can deliver 1.4W into 8Ω (MAX4364) or 1W into 8Ω
(MAX4365) while operating from a single 5V supply.
These devices consist of two high-output-current op
amps configured as a bridge-tied load (BTL) amplifier
(see Typical Application Circuit/Functional Diagram).
The gain of the device is set by the closed-loop gain of
the input op amp. The output of the first amplifier
serves as the input to the second amplifier, which is
configured as an inverting unity-gain follower in both
devices. This results in two outputs, identical in magnitude, but 180° out of phase.
MAX4364/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
The increase in power delivered by the BTL configuration directly results in an increase in internal power dissipation over the single-ended configuration. The
maximum power dissipation for a given VCC and load is
given by the following equation:
PDISS(MAX) =
2
π RL
Efficiency
The efficiency of the MAX4364/MAX4365 is calculated
by taking the ratio of the power delivered to the load to
the power consumed from the power supply. Output
power is calculated by the following equations:
V
POUT = PEAK
2RL
2
where VPEAK is half the peak-to-peak output voltage. In
BTL amplifiers, the supply current waveform is a fullwave rectified sinusoid with the magnitude proportional
to the peak output voltage and load. Calculate the supply current and power drawn from the power supply by
the following:
10
The efficiency of the MAX4364/MAX4365 is:
2VCC2
If the power dissipation for a given application exceeds
the maximum allowed for a given package, reduce
VCC, increase load impedance, decrease the ambient
temperature or add heat sinking to the device. Large
output, supply, and ground PC board traces improve
the maximum power dissipation in the package.
Thermal-overload protection limits total power dissipation in the MAX4364/MAX4365. 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 conditions as the device heats
and cools.
The MAX4365 QFN package features an exposed thermal pad on its underside. This pad lowers the thermal
resistance of the package by providing a direct heat
conduction path from the die to the PC board. Connect
the exposed thermal pad to circuit ground by using a
large pad, ground plane, or multiple vias to the ground
plane.
ICC =
 2V

PIN = VCC  PEAK 
 πRL 
2VPEAK
πRL
P
η = OUT =
PIN
POUTRL
2
2VCC
π
The device efficiency values in Table 1 are calculated
based on the previous equation and do include the
effects of quiescent current. Note that efficiency is low
at low output-power levels, but remains relatively constant at normal operating, output-power levels.
Component Selection
Gain-Setting Resistors
External feedback components set the gain of both
devices. Resistors RF and RIN (see Typical Application
Circuit/Functional Diagram) set the gain of the amplifier
as follows:
A VD = 2 ×
RF
RIN
Optimum output offset is achieved when RF = 20kΩ.
Vary the gain by changing the value of RIN. When using
the MAX4364/MAX4365 in a high-gain configuration
(greater than 8V/V), a feedback capacitor may be
required to maintain stability (see Figure 2). CF and RF
limit the bandwidth of the device, preventing high-frequency oscillations. Ensure that the pole created by CF
and RF is not within the frequency band of interest.
Input Filter
The input capacitor (CIN), in conjunction with RIN forms
a highpass filter that removes the DC bias from an
incoming signal. 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:
ƒ −3dB =
1
2πRINCIN
Choose RIN according to the Gain-Setting Resistors
section. Choose CIN such that f-3dB is well below the
lowest frequency of interest. Setting f -3dB too high
affects the low-frequency response of the amplifier. Use
capacitors whose dielectrics have low-voltage coeffi-
______________________________________________________________________________________
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
MAX4364/MAX4365
VCC
6
CLICKLESS/
POPLESS
SHUTDOWN
CONTROL
VCC
50kΩ
2
SHDN
1
OUT-
8
BIAS
CBIAS
50kΩ
3
IN+
10kΩ
10kΩ
OUT+ 5
CIN
AUDIO INPUT
RIN
4
IN-
MAX4364
MAX4365
GND
7
RF
CF
Figure 2. High-Gain Configuration
Table 1. Efficiency in a 5V, 8Ω BTL System
OUTPUT
POWER (W)
INTERNAL POWER
DISSIPATION (W)
EFFICIENCY (%)
0.25
0.55
31.4
0.50
0.63
44.4
0.75
0.63
54.4
1.00
0.59
62.8
1.25
0.53
70.2
1.40
0.48
74.3
cients, such as tantalum or aluminum electrolytic.
Capacitors with high-voltage coefficients, such as
ceramics, may result in an increase distortion at low
frequencies.
Other considerations when designing the input filter
include the constraints of the overall system, the actual
frequency band of interest and click-and-pop suppression. Although high-fidelity audio calls for a flat gain
response between 20Hz and 20kHz, portable voicereproduction devices such as cellular phones and twoway radios need only concentrate on the frequency
range of the spoken human voice (typically 300Hz to
3.5kHz). In addition, speakers used in portable devices
typically have a poor response below 150Hz. Taking
these two factors into consideration, the input filter may
not need to be designed for a 20Hz to 20kHz response,
saving both board space and cost due to the use of
smaller capacitors.
BIAS Capacitor
The BIAS bypass capacitor, CBIAS, improves PSRR and
THD + N by reducing power-supply noise at the common-mode bias node, and serves as the primary clickand-pop suppression mechanism. CBIAS is fed from an
internal 25kΩ source, and controls the rate at which the
common-mode bias voltage rises at startup and falls
during shutdown. For optimum click-and-pop suppression, ensure that the input capacitor (C IN ) is fully
charged (ten time constants) before CBIAS. The value of
CBIAS for best click-and-pop suppression is given by:
C R 
CBIAS ≤ 10 IN IN 
 25kΩ 
In addition, a larger CBIAS value yields higher PSRR.
______________________________________________________________________________________
11
MAX4364/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
Clickless/Popless Operation
Proper selection of AC-coupling capacitors (CIN) and
CBIAS achieves clickless/popless shutdown and startup.
The value of CBIAS determines the rate at which the
midrail bias voltage rises on startup and falls when entering shutdown. The size of the input capacitor also affects
clickless/popless operation. On startup, CIN is charged
to its quiescent DC voltage through the feedback resistor
(RF) from the output. This current creates a voltage transient at the amplifier’s output, which can result in an
audible pop. Minimizing the size of CIN reduces this
effect, optimizing click-and-pop suppression.
Supply Bypassing
Proper supply bypassing ensures low-noise, low-distortion performance. Place a 0.1µF ceramic capacitor in
parallel with a 10µF ceramic capacitor from V CC to
GND. Locate the bypass capacitors as close to the
device as possible.
Adding Volume Control
The addition of a digital potentiometer provides simple
volume control. Figure 3 shows the MAX4364/MAX4365
with the MAX5407 log taper digital potentiometer used
as an input attenuator. Connect the high terminal of the
MAX5407 to the audio input, the low terminal to ground
and the wiper to CIN. Setting the wiper to the top posi-
RF
AUDIO
INPUT
1 H
MAX5407
4 L
OUT+
RIN
W 3
IN- MAX4364
CIN
MAX4365
OUT-
Figure 3. MAX4364/MAX4365 and MAX5160 Volume Control
Circuit
tion passes the audio signal unattenuated. Setting the
wiper to the lowest position fully attenuates the input.
Layout Considerations
Good layout improves performance by decreasing the
amount of stray capacitance and noise at the amplifier’s
inputs and outputs. Decrease stray capacitance by minimizing PC board trace lengths, using surface-mount
components and placing external components as close
to the device as possible. Also refer to the Power
Dissipation section for heatsinking considerations.
Pin Configurations
Chip Information
MAX4364 TRANSISTOR COUNT: 772
MAX4365 TRANSISTOR COUNT: 768
TOP VIEW
SHDN
1
BIAS
2
8
OUT-
7
GND
3
6
VCC
IN- 4
5
OUT+
8
OUT-
7
SHDN
3
6
VCC
IN- 4
5
OUT+
PROCESS: BiCMOS
MAX4364
IN+
SO
BIAS
1
IN+
2
MAX4365
GND
µMAX/QFN
12
______________________________________________________________________________________
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
N
E
H
INCHES
MILLIMETERS
MAX
MIN
0.069
0.053
0.010
0.004
0.014
0.019
0.007
0.010
0.050 BSC
0.150
0.157
0.228
0.244
0.016
0.050
MAX
MIN
1.35
1.75
0.10
0.25
0.35
0.49
0.19
0.25
1.27 BSC
3.80
4.00
5.80
6.20
0.40
SOICN .EPS
DIM
A
A1
B
C
e
E
H
L
1.27
VARIATIONS:
1
INCHES
TOP VIEW
DIM
D
D
D
MIN
0.189
0.337
0.386
MAX
0.197
0.344
0.394
MILLIMETERS
MIN
4.80
8.55
9.80
MAX
5.00
8.75
10.00
N MS012
8
AA
14
AB
16
AC
D
A
B
e
C
0∞-8∞
A1
L
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE, .150" SOIC
APPROVAL
DOCUMENT CONTROL NO.
21-0041
REV.
B
1
1
______________________________________________________________________________________
13
MAX4364/MAX4365
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.)
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.)
6, 8, &10L, QFN THIN.EPS
MAX4364/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
PACKAGE OUTLINE, 6, 8 & 10L,
QFN THIN (DUAL), EXPOSED PAD, 3x3x0.80 mm
21-0137
C
COMMON DIMENSIONS
SYMBOL
A
MIN.
0.70
0.80
D
2.90
MAX.
3.10
E
2.90
3.10
A1
0.00
0.05
L
k
0.20
0.40
0.25 MIN
A2
0.20 REF.
PACKAGE VARIATIONS
PKG. CODE
N
D2
E2
e
JEDEC SPEC
b
T633-1
6
1.50±0.10
2.30±0.10
0.95 BSC
MO229 / WEEA
0.40±0.05
1.90 REF
T833-1
8
1.50±0.10
2.30±0.10
0.65 BSC
MO229 / WEEC
0.30±0.05
1.95 REF
T1033-1
10
1.50±0.10
2.30±0.10
0.50 BSC
MO229 / WEED-3
0.25±0.05
2.00 REF
[(N/2)-1] x e
PACKAGE OUTLINE, 6, 8 & 10L,
QFN THIN (DUAL), EXPOSED PAD, 3x3x0.80 mm
21-0137
14
C
______________________________________________________________________________________
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
E
ÿ 0.50±0.1
8
INCHES
DIM
A
A1
A2
b
H
c
D
e
E
H
0.6±0.1
1
L
1
α
0.6±0.1
S
BOTTOM VIEW
D
MIN
0.002
0.030
MAX
0.043
0.006
0.037
0.014
0.010
0.007
0.005
0.120
0.116
0.0256 BSC
0.120
0.116
0.198
0.188
0.026
0.016
6∞
0∞
0.0207 BSC
8LUMAXD.EPS
4X S
8
MILLIMETERS
MAX
MIN
0.05
0.75
1.10
0.15
0.95
0.25
0.36
0.13
0.18
2.95
3.05
0.65 BSC
2.95
3.05
4.78
5.03
0.41
0.66
0∞
6∞
0.5250 BSC
TOP VIEW
A1
A2
e
A
α
c
b
L
SIDE VIEW
FRONT VIEW
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE, 8L uMAX/uSOP
APPROVAL
DOCUMENT CONTROL NO.
21-0036
REV.
J
1
1
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 ____________________ 15
© 2002 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
MAX4364/MAX4365
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.)