General Description
The MAX4364/MAX4365 are bridged audio power
amplifiers intended for portable audio devices with
internal speakers. The MAX4364 is capable of deliver-
ing 1.4W from a single 5V supply and 500mW from a
single 3V supply into an 8Ωload. The MAX4365 is
capable of delivering 1W from a single 5V supply and
450mW from a single 3V supply into an 8Ωload. 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 exter-
nal 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
3mm 0.8mm) and µMAX®packages.
Applications
Cellular Phones
PDAs
Two-Way Radios
General-Purpose Audio
Features
o1.4W into 8Ω Load (MAX4364)
o1W into 8Ω Load (MAX4365)
o0.04% THD+N at 1kHz
o68dB PSRR at 217Hz
o2.7V to 5.5V Single-Supply Operation
o5mA Supply Current
oLow-Power, 10nA Shutdown Mode
oPin Compatible with the LM4861/LM4862/LM4864
(MAX4364)
oClickless Power-Up and Shutdown
oThermal-Overload and Short-Circuit Protection
oAvailable in TDFN, µMAX, and SO Packages
MAX4364/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
________________________________________________________________
Maxim Integrated Products
1
Ordering Information
19-2387; Rev 4; 5/11
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.
PART TEMP RANGE PIN-PACKAGE TOP
MARK
MAX4364ESA+ -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
Typical Application Circuit/Functional Diagram
Pin Configurations appear at end of data sheet.
*
EP = Exposed pad.
+
Denotes a lead(Pb)-free/RoHS-compliant package.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
MAX4364/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
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.
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
ELECTRICAL CHARACTERISTICS—5V
(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
MAX4364 7 13
M AX 4364, TA
= TM IN
to TM AX 17
M AX 4365 5 8
Supply Current ICC (Note 4)
M AX 4365, TA
= TM IN
to TM AX 11
mA
Shutdown Supply Current ISHDN VSHDN = VCC 0.01 4 µA
TA = +25°C VCC x
0.7
VIH TA = -40°C to +85°C
(Note 5)
VCC x
0.7
TA = +25°C VCC x
0.3
SHDN Threshold
VIL TA = -40°C to +85°C
(Note 5)
VCC x
0.3
V
Common-Mode Bias Voltage VBIAS (Note 6) VCC/2 -
5% VCC/2 VCC/2
+ 5% V
Output Offset Voltage VOS IN- = OUT+, IN+ = BIAS (Note 7) ±1±10 mV
VCC = 2.7V to 5.5V DC 55 75
217Hz 68
Power-Supply Rejection Ratio PSRR VRIPPLE = 200mVP-P,
RL = 8Ω1kHz 58
dB
MAX4364 1200 1400
Output Power POUT RL = 8Ω, THD+N = 1%,
fIN = 1kHz (Note 8) MAX4365 800 1000 mW
Note 1: Continuous power dissipation must also be observed.
PACKAGE THERMAL CHARACTERISTICS (Note 2)
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.maxim-ic.com/thermal-tutorial.
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
MAX4364/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS—3V
(VCC = 3V, RL= ∞, CBIAS = 1µF to GND, VSHDN = VGND, TA= +25°C, unless otherwise noted.) (Note 3)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX4364 6
Supply Current ICC (Note 4) MAX4365 4.5 mA
Shutdown Supply Current ISHDN VSHDN = VCC 10 nA
MAX4364 400 500
Output Power POUT
RL = 8Ω, THD+N =
1%, fIN = 1kHz
(Note 8) MAX4365 350 450
mW
MAX4364,
POUT = 400mW 0.05
Total Harmonic Distortion Plus
Noise THD + N AV = -2V/V, RL = 8Ω,
fIN = 1kHz (Notes 5, 9) MAX4365,
POUT = 400mW 0.08
%
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.
ELECTRICAL CHARACTERISTICS—5V (continued)
(VCC = 5V, RL= ∞, CBIAS = 1µF to GND, VSHDN = VGND, TA= +25°C, unless otherwise noted.) (Note 3)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX4364,
POUT = 1W 0.04
Total Harmonic Distortion Plus
Noise THD+N AV = -2V/V, RL = 8Ω,
fIN = 1kHz (Notes 5, 9) 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
TA = +25°C 50
Power-Up Time tPU CBIAS = 0.22µF, TA = -40°C to +85°C
(Note 5) 14 35 ms
Shutdown Time tSHDN 10 µs
TA = +25°C 50
Enable Time from Shutdown tENABLE CBIAS = 0.22µF, TA = -40°C to +85°C
(Note 5) 12 35 ms
MAX4364/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
4 _______________________________________________________________________________________
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
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
1650100052020040
0.01
0.1
1
10
100
0.001
02450
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 toc06
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
010k
VCC = 3V
AV = 20V/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
010k
VCC = 3V
AV = 4V/V
RL = 8Ω
0.25W
0.4W
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364 toc04
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
010k
VCC = 3V
AV = 2V/V
RL = 8Ω
0.25W
0.4W
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364 toc01
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
010k
VCC = 5V
AV = 2V/V
RL = 8Ω
0.25W
0.5W
1W
MAX4364 toc02
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
010k
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
010k
VCC = 5V
AV = 20V/V
RL = 8Ω
0.25W
0.5W
1W
MAX4364
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
Typical Operating Characteristics
(VCC = 5V, THD+N measurement bandwidth = 22Hz to 22kHz, TA= +25°C, unless otherwise noted.)
MAX4364/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
_______________________________________________________________________________________
5
Typical Operating Characteristics (continued)
(VCC = 5V, THD+N measurement bandwidth = 22Hz to 22kHz, TA= +25°C, unless otherwise noted.)
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
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
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
POWER DISSIPATION vs. OUTPUT POWER
MAX4364 toc15
OUTPUT POWER (mW)
POWER DISSIPATION (mW)
300200100
30
90
210
270
300
0
0500
400
VCC = 3V
fIN = 1kHz
RL = 8Ω
150
60
120
240
180
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
OUTPUT POWER vs. LOAD RESISTANCE
MAX4364 toc13
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
302010
200
400
800
1000
1200
0
050
40
600
VCC = 3V
fIN = 1kHz
10% THD+N
1% THD+N
MAX4364
OUTPUT POWER vs. LOAD RESISTANCE
MAX4364 toc12
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
302010
600
1200
1800
2400
3000
0
050
40
VCC = 5V
fIN = 1kHz
10% THD+N
1% THD+N
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
1650100052020040
0.01
0.1
1
10
100
0.001
02440
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/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(VCC = 5V, THD+N measurement bandwidth = 22Hz to 22kHz, TA= +25°C, unless otherwise noted.)
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 toc24
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
010k
VCC = 3V
AV = 4V/V
RL = 8Ω
0.25W
0.4W
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364 toc23
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
010k
VCC = 3V
AV = 2V/V
RL = 8Ω
0.25W
0.4W
MAX4364 toc22
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
010k
VCC = 5V
AV = 20V/V
RL = 8Ω
0.25W
0.5W
0.75W
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
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 toc25
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
010k
VCC = 3V
AV = 20V/V
RL = 8Ω
0.25W
0.4W
MAX4365
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
MAX4364 toc21
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
010k
VCC = 5V
AV = 4V/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 toc20
FREQUENCY (Hz)
THD+N (%)
100 1k
0.1
1
10
0.01
010k
VCC = 5V
AV = 2V/V
RL = 8Ω
0.25W
0.5W
0.75W
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/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
_______________________________________________________________________________________
7
Typical Operating Characteristics (continued)
(VCC = 5V, THD+N measurement bandwidth = 22Hz to 22kHz, TA= +25°C, unless otherwise noted.)
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
POWER DISSIPATION vs. OUTPUT POWER
MAX4364 toc34
OUTPUT POWER (mW)
POWER DISSIPATION (mW)
300200100
50
100
150
200
250
0
0500
400
VCC = 3V
RL = 8Ω
fIN = 1kHz
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
OUTPUT POWER vs. LOAD RESISTANCE
MAX4364 toc32
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
302010
400
600
800
1000
1200
0
050
10% THD+N
1% THD+N
40
VCC = 3V
fIN = 1kHz
200
MAX4365
OUTPUT POWER vs. LOAD RESISTANCE
MAX4364 toc31
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
302010
200
400
600
800
1000
1200
0
050
40
VCC = 5V
fIN = 1kHz
MAX4365
SUPPLY CURRENT vs. TEMPERATURE
MAX4364 toc36
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
3510-15
4
5
6
7
3
-40 85
60
VCC = 5V
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
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
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/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
8 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(VCC = 5V, THD+N measurement bandwidth = 22Hz to 22kHz, TA= +25°C, unless otherwise noted.)
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
Pin Description
PIN
MAX4364 MAX4365
SO µMAX/TDFN
NAME FUNCTION
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 Amplifier Positive Output
66V
CC Power Supply
7 3 GND Ground
8 8 OUT- Bridged Amplifier 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. TEMPERATURE
MAX4364 toc38
TEMPERATURE (°C)
SUPPLY CURRENT (nA)
3510-15
20
30
10
40
50
60
70
80
0
-40 85
60
VCC = 5V
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
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 inverting unity-gain follower in both
devices. This results in two outputs, identical in magni-
tude, 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 inter-
nally connected to the noninverting input of one amplifi-
er, 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
shutdown mode that reduces quiescent current con-
sumption. 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 nor-
mal operation.
Current Limit
The MAX4364/MAX4365 feature a current limit that pro-
tects the device during output short circuit and over-
load conditions. When both amplifier outputs are
shorted to either VCC or GND, the short-circuit protec-
tion 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 similar conditions. Thus, the differential gain of
the device is twice the closed-loop gain of the input
amplifier. The effective gain is given by:
Substituting 2 VOUT(P-P) into the following equations
yields four times the output power due to doubling of
the output voltage.
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:
where TJ(MAX) is +150°C, TAis 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.
PTT
DISSPKG MAX J MAX A
JA
() ()
=−
θ
VV
PV
R
RMS OUT P P
OUT RMS
L
=
=
−()
22
2
AR
R
VD F
IN
=×2
MAX4364/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
_______________________________________________________________________________________ 9
+1 VOUT(P-P)
2 x VOUT(P-P)
VOUT(P-P)
-1
Figure 1. Bridge-Tied Load Configuration
MAX4364/MAX4365
The increase in power delivered by the BTL configura-
tion directly results in an increase in internal power dis-
sipation over the single-ended configuration. The
maximum power dissipation for a given VCC and load is
given by the following equation:
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 dissipa-
tion in the MAX4364/MAX4365. When the junction tem-
perature exceeds +160°C, the thermal protection
circuitry disables the amplifier output stage. The ampli-
fiers are enabled once the junction temperature cools
by 15°C. This results in a pulsing output under continu-
ous thermal overload conditions as the device heats
and cools.
The MAX4365 TDFN package features an exposed
thermal pad on its underside. This pad lowers the ther-
mal 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.
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:
where VPEAK is half the peak-to-peak output voltage. In
BTL amplifiers, the supply current waveform is a full-
wave rectified sinusoid with the magnitude proportional
to the peak output voltage and load. Calculate the sup-
ply current and power drawn from the power supply by
the following:
The efficiency of the MAX4364/MAX4365 is:
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 con-
stant at normal operating, output-power levels.
Component Selection
Gain-Setting Resistors
External feedback components set the gain of both
devices. Resistors RFand RIN (see
Typical Application
Circuit/Functional Diagram
) set the gain of the amplifier
as follows:
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). CFand RF
limit the bandwidth of the device, preventing high-fre-
quency oscillations. Ensure that the pole created by CF
and RFis 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:
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-
AR
R
VD F
IN
=×2
η
π
==
P
P
PR
V
OUT
IN
OUT L
CC
2
2
PV V
R
IN CC PEAK
L
=⎛
⎝
⎜⎞
⎠
⎟
2
π
IV
R
CC PEAK
L
=2
π
PV
R
OUT PEAK
L
=2
2
PV
R
DISS MAX CC
L
()
=22
2
π
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
10 ______________________________________________________________________________________
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 suppres-
sion. Although high-fidelity audio calls for a flat gain
response between 20Hz and 20kHz, portable voice-
reproduction devices such as cellular phones and two-
way 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 click-and-
pop suppression mechanism. CBIAS is fed from an
internal 25kΩsource, and controls the rate at which the
common-mode bias voltage rises at startup and falls
during shutdown. For optimum click-and-pop suppres-
sion, 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 addition, a larger CBIAS value yields higher PSRR.
CCR
k
BIAS IN IN
≥⎡
⎣
⎢⎤
⎦
⎥
10 25 Ω
MAX4364/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
______________________________________________________________________________________ 11
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
Figure 2. High-Gain Configuration
Table 1. Efficiency in a 5V, 8Ω BTL System
MAX4364/MAX4365
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 enter-
ing 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 tran-
sient 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-distor-
tion 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 posi-
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 min-
imizing 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.
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
12 ______________________________________________________________________________________
OUT+
AUDIO
INPUT
OUT-
IN-
1H
W3
CIN
RF
RIN
4L
MAX4364
MAX4365
MAX5407
Figure 3. MAX4364/MAX4365 and MAX5160 Volume Control
Circuit
Chip Information
PROCESS: BiCMOS
µMAX
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.
+
45
MAX4365
MAX4364
MAX4365
VCC
OUT+IN-
1
2
8
7
OUT-
+
GNDBIAS
IN+
SHDN
SO
TOP VIEW
3
4
6
5
MAX4364
Pin Configurations
MAX4364/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
______________________________________________________________________________________ 13
Package Information
For the latest package outline information and land patterns (footprints), go to www.maxim-ic.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 per-
tains to the package regardless of RoHS status.
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
MAX4364/MAX4365
1.4W and 1W, Ultra-Small, Audio Power
Amplifiers with Shutdown
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.
14
____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2011 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
4 5/11
Added EP information to Pin Description; updated Ordering Information and Pin
Configurations for lead-free parts; updated specifications in Absolute Maximum
Ratings, Package Thermal Characteristics and Electrical Characteristics sections
1, 2, 3, 8, 9,
12, 13