19-2387; Rev 5; 6/17
μMAX is a registered trademark of Maxim Integrated Products, Inc.
Pin Configurations appear at end of data sheet.
General Description
The MAX4364/MAX4365 are bridged audio power ampli-
fiers 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 sup-
ply 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.
The MAX4364 is available in a small 8-pin SO package.
The MAX4365 is available in tiny 8-pin TDFN (3mm x
3mm x 0.8mm) and μMAX® packages.
Applications
●Cellular Phones
●PDAs
●Two-Way Radios
●General-Purpose Audio
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 TDFN, μMAX, and SO Packages
*EP = Exposed pad.
+Denotes a lead(Pb)-free/RoHS-compliant package.
/V denotes an automotive qualified part.
T = Tape and reel.
PART TEMP RANGE PIN-PACKAGE TOP
MARK
MAX4364ESA/V+T -40°C to +85°C 8 SO —
MAX4365EUA+ -40°C to +85°C 8 µMAX —
MAX4365ETA+ -40°C to +85°C 8 TDFN-EP* ACD
VCC
VCC
6
2
3
4
1
8
5
7
OUT-
IN-
IN+
BIAS
CBIAS
CIN RIN
RF
50kΩ
50kΩ
10kΩ
10kΩ
AUDIO
INPUT
CLICKLESS/POPLESS
SHUTDOWN CONTROL
GND
SHDN
OUT+
MAX4364
MAX4364/MAX4365 1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
Typical Application Circuit/Functional Diagram
Ordering Information
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 4.8mW/°C above +70°C) ............388mW
8-Pin TDFN (derate 24.4mW/°C above +70°C) ........1951mW
8-Pin SO (derate 7.8mW/°C above +70°C) ................. 623mW
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
Soldering Temperature (reflow) .......................................+260°C
(Note 2)
(VCC = 5V, RL = ∞, CBIAS = 1μF to GND, VSHDN = VGND, TA = +25°C, unless otherwise noted.) (Note 3)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Voltage Range VCC Inferred from PSRR test 2.7 5.5 V
Supply Current ICC (Note 4)
MAX4364 7 13
mA
MAX4364, TA = TMIN to TMAX 17
MAX4365 5 8
MAX4365, TA = TMIN to TMAX 11
Shutdown Supply Current ISHDN VSHDN = VCC 0.01 4 µA
SHDN Threshold
VIH
TA = +25°C VCC x
0.7
V
TA = -40°C to +85°C
(Note 5)
VCC x
0.7
VIL
TA = +25°C VCC x
0.3
TA = -40°C to +85°C
(Note 5)
VCC x
0.3
Common-Mode Bias Voltage VBIAS (Note 6) VCC/2 -
5% VCC/2 VCC/2
+ 5% V
Output Oset Voltage VOS IN- = OUT+, IN+ = BIAS (Note 7) ±1 ±10 mV
Power-Supply Rejection Ratio PSRR
VCC = 2.7V to 5.5V DC 55 75
dB
VRIPPLE = 200mVP-P,
RL = 8Ω
217Hz 68
1kHz 58
Output Power POUT
RL = 8Ω, THD+N = 1%,
fIN = 1kHz (Note 8)
MAX4364 1200 1400 mW
MAX4365 800 1000
MAX4364/MAX4365 1.4W and 1W, Ultra-Small, Audio Power
Ampliers with Shutdown
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│
2
Absolute Maximum Ratings
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
μMAX
Junction-to-Ambient Thermal Resistance (θJA) .....206.3°C/W
Junction-to-Case Thermal Resistance (θJC) ...............42°C/W
TDFN
Junction-to-Ambient Thermal Resistance (θJA) ..........41°C/W
Junction-to-Case Thermal Resistance (θJC) .................8°C/W
SO
Junction-to-Ambient Thermal Resistance (θJA) .....128.4°C/W
Junction-to-Case Thermal Resistance (θJC) ...............36°C/W
Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
Note 1: Continuous power dissipation must also be observed.
Package Thermal Characteristics
(VCC = 3V, RL = ∞, CBIAS = 1μF to GND, VSHDN = VGND, TA = +25°C, unless otherwise noted.) (Note 3)
(VCC = 5V, RL = ∞, CBIAS = 1μF to GND, VSHDN = VGND, TA = +25°C, unless otherwise noted.) (Note 3)
Note 3: All specifications are 100% tested at TA = +25°C.
Note 4: 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 5: Guaranteed by design, not production tested.
Note 6: Common-mode bias voltage is the voltage on BIAS and is nominally VCC/2.
Note 7: Maximum differential-output offset voltage is tested in a unity-gain configuration. VOS = VOUT+ - VOUT-.
Note 8: Output power is specified by a combination of a functional output-current test, and characterization analysis.
Note 9: Measurement bandwidth for THD+N is 22Hz to 22kHz.
Note 10: Extended short-circuit conditions result in a pulsed output.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Total Harmonic Distortion Plus
Noise THD+N AV = -2V/V, RL = 8Ω,
fIN = 1kHz (Notes 5, 9)
MAX4364,
POUT = 1W 0.04
%
MAX4365,
POUT = 750mW 0.1
Noise fIN = 10kHz, BW = 22Hz to 22kHz 12 µVRMS
Short-Circuit Current ISC OUT+ to OUT- (Note 10) 600 mA
Thermal Shutdown Threshold 160 oC
Thermal Shutdown Hysteresis 15 oC
Power-Up Time tPU
TA = +25°C 50
ms
CBIAS = 0.22µF, TA = -40°C to +85°C
(Note 5) 14 35
Shutdown Time tSHDN 10 µs
Enable Time from Shutdown tENABLE
TA = +25°C 50
ms
CBIAS = 0.22µF, TA = -40°C to +85°C
(Note 5) 12 35
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Current ICC (Note 4) MAX4364 6 mA
MAX4365 4.5
Shutdown Supply Current ISHDN VSHDN = VCC 10 nA
Output Power POUT
RL = 8Ω, THD+N =
1%, fIN = 1kHz
(Note 8)
MAX4364 400 500
mW
MAX4365 350 450
Total Harmonic Distortion Plus
Noise THD + N AV = -2V/V, RL = 8Ω,
fIN = 1kHz (Notes 5, 9)
MAX4364,
POUT = 400mW 0.05
%
MAX4365,
POUT = 400mW 0.08
MAX4364/MAX4365 1.4W and 1W, Ultra-Small, Audio Power
Ampliers with Shutdown
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│
3
Electrical Characteristics—3V
Electrical Characteristics—5V (continued)
(VCC = 5V, THD+N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
MAX4364 toc02
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
0 10k
VCC = 5V
AV = 4V/V
RL = 8Ω
0.25W
0.5W
1W
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364 toc03
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
0 10k
VCC = 5V
AV = 20V/V
RL = 8Ω
0.25W
0.5W
1W
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364 toc04
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
0 10k
VCC = 3V
AV = 2V/V
RL = 8Ω
0.25W
0.4W
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364 toc05
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
0 10k
VCC = 3V
AV = 4V/V
RL = 8Ω
0.25W
0.4W
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364 toc06
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
0 10k
VCC = 3V
AV = 20V/V
RL = 8Ω
0.25W
0.4W
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
1650100052020040
0.01
0.1
1
10
100
0.001
0 2450
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX4364 toc07
OUTPUT POWER (mW)
THD+N (%)
VCC = 5V
AV = 2V/V
RL = 8Ω
20kHz
1kHz
20Hz
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364 toc01
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
0 10k
VCC = 5V
AV = 2V/V
RL = 8Ω
0.25W
0.5W
1W
1650100052020040
0.01
0.1
1
10
100
0.001
0 2450
MAX4364 toc08
OUTPUT POWER (mW)
THD+N (%)
VCC = 5V
AV = 4V/V
RL = 8Ω
20Hz
20kHz
1kHz
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
1700100052519020
0.01
0.1
1
10
100
0.001
0 2500
MAX4364 toc09
OUTPUT POWER (mW)
THD+N (%)
VCC = 3V
AV = 2V/V
RL = 8Ω
20kHz
20Hz
1kHz
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX4364/MAX4365 1.4W and 1W, Ultra-Small, Audio Power
Ampliers with Shutdown
Maxim Integrated
│
4
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Typical Operating Characteristics
(VCC = 5V, THD+N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
1650100052020040
0.01
0.1
1
10
100
0.001
0 2440
MAX4364 toc10
OUTPUT POWER (mW)
THD+N (%)
VCC = 3V
AV = 4V/V
RL = 8Ω
20kHz
20Hz
1kHz
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX4364
OUTPUT POWER vs. SUPPLY VOLTAGE
MAX4364 toc11
SUPPLY VOLTAGE (V)
OUTPUT POWER (mW)
4.84.13.4
500
1000
1500
2000
2500
0
2.7 5.5
RL = 8Ω
fIN = 1kHz
1% THD+N
10% THD+N
MAX4364
OUTPUT POWER vs. LOAD RESISTANCE
MAX4364 toc12
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
302010
600
1200
1800
2400
3000
0
0 50
40
VCC = 5V
fIN = 1kHz
10% THD+N
1% THD+N
MAX4364
OUTPUT POWER vs. LOAD RESISTANCE
MAX4364 toc13
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
302010
200
400
800
1000
1200
0
0 50
40
600
VCC = 3V
fIN = 1kHz
10% THD+N
1% THD+N
MAX4364
POWER DISSIPATION vs. OUTPUT POWER
MAX4364 toc14
OUTPUT POWER (mW)
POWER DISSIPATION (mW)
900600300
70
210
490
630
700
0
0 1500
1200
VCC = 5V
fIN = 1kHz
RL = 8Ω
350
140
280
560
420
MAX4364
POWER DISSIPATION vs. OUTPUT POWER
MAX4364 toc15
OUTPUT POWER (mW)
POWER DISSIPATION (mW)
300200100
30
90
210
270
300
0
0 500
400
VCC = 3V
fIN = 1kHz
RL = 8Ω
150
60
120
240
180
MAX4364
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX4364 toc16
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
4.84.13.4
6.5
7.0
7.5
8.0
9.0
6.0
2.7 5.5
8.5
MAX4364
SUPPLY CURRENT vs. TEMPERATURE
MAX4364 toc17
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
3510-15
6
7
8
9
10
5
-40 85
60
VCC = 5V
MAX4364
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX4364 toc18
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (nA)
4.84.13.4
2
4
6
8
12
0
2.7 5.5
10
MAX4364/MAX4365 1.4W and 1W, Ultra-Small, Audio Power
Ampliers with Shutdown
Maxim Integrated
│
5
www.maximintegrated.com
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
MAX4364 toc20
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
0 10k
VCC = 5V
AV = 2V/V
RL = 8Ω
0.25W
0.5W
0.75W
MAX4364 toc21
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
0 10k
VCC = 5V
AV = 4V/V
RL = 8Ω
0.25W
0.5W
0.75W
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364 toc22
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
0 10k
VCC = 5V
AV = 20V/V
RL = 8Ω
0.25W
0.5W
0.75W
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364 toc23
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
0 10k
VCC = 3V
AV = 2V/V
RL = 8Ω
0.25W
0.4W
MAX4364 toc24
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
0 10k
VCC = 3V
AV = 4V/V
RL = 8Ω
0.25W
0.4W
MAX4364 toc25
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
0 10k
VCC = 3V
AV = 20V/V
RL = 8Ω
0.25W
0.4W
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX4364 toc19
TEMPERATURE (°C)
SUPPLY CURRENT (nA)
3510-15
20
40
60
80
100
0
-40 85
60
VCC = 5V
MAX4364 toc26
OUTPUT POWER (mW)
THD+N (%)
2000160013001000700500300200
0.01
0.1
1
10
100
0.001
0 2400
VCC = 5V
AV = 2V/V
RL = 8Ω
20kHz
20Hz
1kHz
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX4364 toc27
OUTPUT POWER (mW)
THD+N (%)
2000160013001000750500
0.01
0.1
1
10
100
0.001
2400
VCC = 5V
AV = 4V/V
RL = 8Ω
20kHz
20Hz
1kHz
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX4364/MAX4365 1.4W and 1W, Ultra-Small, Audio Power
Ampliers with Shutdown
Maxim Integrated
│
6
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Typical Operating Characteristics (continued)
(VCC = 5V, THD+N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
MAX4364 toc28
OUTPUT POWER (mW)
THD+N (%)
725600500400325
250
200125
0.01
0.1
1
10
100
0.001
0 800 1000
VCC = 3V
AV = 2V/V
RL = 8Ω
20kHz
20Hz
1kHz
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX4364 toc29
OUTPUT POWER (mW)
THD+N (%)
725600500400325
250
200125
0.01
0.1
1
10
100
0.001
0 850 1000
VCC = 3V
AV = 4V/V
RL = 8Ω
20kHz
20Hz
1kHz
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. OUTPUT POWER
MAX4365
OUTPUT POWER vs. SUPPLY VOLTAGE
MAX4364 toc30
SUPPLY VOLTAGE (V)
OUTPUT POWER (mW)
4.84.13.4
500
1000
1500
2000
2500
0
2.7 5.5
RL = 8Ω
fIN = 1kHz
1% THD+N
10% THD+N
MAX4365
OUTPUT POWER vs. LOAD RESISTANCE
MAX4364 toc31
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
302010
200
400
600
800
1000
1200
0
0 50
40
VCC = 5V
fIN = 1kHz
MAX4365
OUTPUT POWER vs. LOAD RESISTANCE
MAX4364 toc32
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
302010
400
600
800
1000
1200
0
0 50
10% THD+N
1% THD+N
40
VCC = 3V
fIN = 1kHz
200
MAX4365
POWER DISSIPATION vs. OUTPUT POWER
MAX4364 toc33
OUTPUT POWER (mW)
POWER DISSIPATION (mW)
900600300
200
400
600
800
0
0 1500
1200
VCC = 5V
RL = 8Ω
fIN = 1kHz
MAX4365
POWER DISSIPATION vs. OUTPUT POWER
MAX4364 toc34
OUTPUT POWER (mW)
POWER DISSIPATION (mW)
300200100
50
100
150
200
250
0
0 500
400
VCC = 3V
RL = 8Ω
fIN = 1kHz
MAX4365
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX4364 toc35
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
4.13.4
4
5
6
7
3
2.7 5.5
4.8
MAX4365
SUPPLY CURRENT vs. TEMPERATURE
MAX4364 toc36
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
3510-15
4
5
6
7
3
-40 85
60
VCC = 5V
MAX4364/MAX4365 1.4W and 1W, Ultra-Small, Audio Power
Ampliers with Shutdown
Maxim Integrated
│
7
www.maximintegrated.com
Typical Operating Characteristics (continued)
(VCC = 5V, THD+N measurement bandwidth = 22Hz to 22kHz, TA = +25°C, unless otherwise noted.)
PIN
NAME FUNCTIONMAX4364 MAX4365
SO µMAX/TDFN
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+ Bridged Amplier Positive Output
6 6 VCC Power Supply
7 3 GND Ground
8 8 OUT- Bridged Amplier Negative Output
— — EP Exposed Pad (TDFN Only). Internally connected to GND. Connect to a large ground
plane to maximize thermal performance. Not intended as an electrical connection point.
MAX4365
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX4364 toc37
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (nA)
4.84.13.4
2
4
6
8
12
0
2.7 5.5
10
MAX4365
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX4364 toc38
TEMPERATURE (°C)
SUPPLY CURRENT (nA)
3510-15
20
30
10
40
50
60
70
80
0
-40 85
60
VCC = 5V
GAIN AND PHASE vs. FREQUENCY
MAX4364 toc39
FREQUENCY (Hz)
GAIN/PHASE (dB/DEGREES)
1M100k10k1k100
-160
-140
-120
-100
-80
-60
-40
-20
0
20
40
60
80
-180
10 10M
AV = 1000V/V
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX4364 toc40
FREQUENCY (Hz)
PSRR (dB)
10k1k100
-70
-60
-50
-40
-30
-20
-80
10 100k
RL = 8Ω
VRIPPLE = 200mVP-P
MAX4364/MAX4365 1.4W and 1W, Ultra-Small, Audio Power
Ampliers with Shutdown
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│
8
Pin Description
Typical Operating Characteristics (continued)
Detailed Description
The MAX4364/MAX4365 bridged audio power ampli-
fiers 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 invert-
ing unity-gain follower in both devices. This results in two
outputs, identical in magnitude, but 180° out of phase.
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.
Shutdown
The MAX4364/MAX4365 feature a 10nA, low-power shut-
down 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 pro-
tects 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 configura-
tion (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 simi-
lar conditions. Thus, the differential gain of the device is
twice the closed-loop gain of the input amplifier. The effec-
tive gain is given by:
= × F
VD IN
R
A2
R
Substituting 2 VOUT(P-P) into the following equations
yields four times the output power due to doubling of the
output voltage.
OUT(P P )
RMS
2
RMS
OUT L
V
V22
V
PR
−
=
=
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,
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:
J(M AX ) A
DISSPKG(MAX) JA
TT
P
−
=θ
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 Package Thermal Characteristics section.
For example, θJA of the μMAX package is 206.3°C/W.
Figure 1. Bridge-Tied Load Configuration
+1 VOUT(P-P)
2 x VOUT(P-P)
VOUT(P-P)
-1
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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 fol-
lowing equation:
2
CC
DISSP(MAX) 2L
2V
P
R
=π
If the power dissipation for a given application exceeds
the maximum allowed for a given package, reduce VCC,
increase load impedance, decrease the ambient tempera-
ture or add heat sinking to the device. Large output, sup-
ply, and ground PC board traces improve the maximum
power dissipation in the package.
Thermal-overload protection limits total power dissipa-
tion in the MAX4364/MAX4365. When the junction tem-
perature 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 TDFN package features an exposed ther-
mal pad on its underside. This pad lowers the thermal
resistance of the package by providing a direct heat con-
duction 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.
Eciency
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:
2
PEAK
OUT
L
V
P2R
=
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 cur-
rent and power drawn from the power supply by the fol-
lowing:
PEAK
CC L
2V
IR
=π
PEAK
IN CC
L
2V
PV R
=
π
The efficiency of the MAX4364/MAX4365 is:
OUT L
OUT
IN CC
PR
P2
P 2V
π
η= =
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:
F
VD IN
R
A2
R
= ×
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 oscil-
lations. 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 incom-
ing 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:
3DB IN IN
1
f2R C
−=π
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-
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cients, such as tantalum or aluminum electrolyt-
ic. 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 con-
sideration, 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 com-
monmode bias node, and serves as the primary click-
andpop 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 dur-
ing shutdown. For optimum click-and-pop suppression,
ensure that the input capacitor (CIN) is fully charged (ten
time constants) before CBIAS. The value of CBIAS for best
click-and-pop suppression is given by:
IN IN
BIAS
CR
C 10 25k
≥
Ω
In addition, a larger CBIAS value yields higher PSRR.
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
VCC
VCC
CIN RIN
RF
CF
CBIAS
6
OUT-
IN+
BIAS
AUDIO INPUT
3
2
CLICKLESS/
POPLESS
SHUTDOWN
CONTROL
GND
SHDN
8
OUT+ 5
7
1
MAX4364
MAX4365
50kΩ
50kΩ
10kΩ
10kΩ
IN-4
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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 mid-
rail 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 resis-
tor (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 VCC 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 position
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 ampli-
fier’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.
Figure 3. MAX4364/MAX4365 and MAX5160 Volume Control
Circuit
OUT+
AUDIO
INPUT
OUT-
IN-
1 H
W 3
CIN
RF
RIN
4 L
MAX4364
MAX4365
MAX5407
MAX
TDFN
2 7 SHDNIN+
8 OUT-1
1234
8765
BIAS +
VCC
GND 3 6
OUT+
SHDNOUT- VCC OUT+
IN-
IN+BIAS GND IN-
EP*
*CONNECT EP TO GND.
+
4 5
MAX4365
MAX4364
MAX4365
VCC
OUT+IN-
1
2
8
7
OUT-
+
GNDBIAS
IN+
SHDN
SO
TOP VIEW
3
4
6
5
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Chip Information
PROCESS: BiCMOS
Pin Congurations
PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND
PATTERN NO.
8 SO S8+5 21-0041 90-0096
8 μMAX U8+1 21-0036 90-0092
8 TDFN T833+2 21-0137 90-0059
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Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
4 5/11
Added EP information to Pin Description; updated Ordering Information and Pin
Congurations for lead-free parts; updated specications in Absolute Maximum
Ratings, Package Thermal Characteristics and Electrical Characteristics sections
1, 2, 3, 8, 9,
12, 13
5 6/17 Changed orderable part number from MAX4364ESA+ to MAX4364ESA/V+T in
Ordering Information table 1
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
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Revision History
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
