General Description
The MAX4366/MAX4367/MAX4368 are bridged audio
power amplifiers intended for devices with internal
speakers and headsets. The MAX4366/MAX4367/
MAX4368 are capable of delivering 330mW of continu-
ous power into a 32Ωload, or 200mW into a 16Ωload
with 1% THD+N from a single 5V supply.
The MAX4366/MAX4367/MAX4368 bridged outputs elimi-
nate the need for output-coupling capacitors minimizing
external component count. The MAX4366/MAX4367/
MAX4368 also feature a low-power shutdown mode,
clickless power-up/power-down and internal DC bias
generation. The MAX4366 is a unity-gain stable, program-
mable gain amplifier. The MAX4367/MAX4368 feature
internally preset gains of 2V/V and 3V/V, respectively.
All devices are available in space-saving 8-pin TDFN
and 8-bump UCSP™ chip-scale packages.
Applications
Cellular Phones
Two-Way Radios
PDAs
Headphones
Headsets
General-Purpose Audio
Features
♦Drives 330mW into 32Ω (200mW into 16Ω)
♦0.02% THD+N at 1kHz (120mW into 32Ω)
♦Internal Bridged Configuration
♦No Output-Coupling Capacitors
♦2.3V to 5.5V Single-Supply Operation
♦2mA Supply Current
♦Low-Power Shutdown Mode
♦Clickless Power-Up and Shutdown
♦Thermal Overload Protection
♦Available in TDFN and UCSP Packages
MAX4366/MAX4367/MAX4368
330mW, Ultra-Small, Audio Power Amplifiers
with Shutdown
________________________________________________________________
Maxim Integrated Products
1
12
B
A
C
UCSP
TOP VIEW
(BUMP SIDE
DOWN)
3
BIAS OUT- SHDN
IN- OUT+ IN+
GND VCC
MAX4366
MAX4367
MAX4368
Pin Configurations
Ordering Information
VCC
VCC
OUT-
IN-
IN+
BIAS
AUDIO
INPUT
CLICKLESS/POPLESS
SHUTDOWNCONTROL
GND
SHDN
OUT+
MAX4367
MAX4368
Typical Operating Circuit
19-2338; Rev 5; 6/08
*
EP = Exposed pad.
+
Denotes a lead-free package.
Ordering Information continued at end of data sheet.
Selector Guide and Functional Diagrams appear at end of
data sheet.
Pin Configurations continued at end of data sheet.
UCSP is a trademark of Maxim Integrated Products, Inc.
PART TEMP RANGE PIN/BUMP-
PACKAGE
TOP
MARK
MAX4366EBL-T -40°C to +85°C 8 UCSP AAK
MAX4366ETA+T -40°C to +85°C 8 TD FN - E P * +AFZ
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim's website at www.maxim-ic.com.
MAX4366/MAX4367/MAX4368
330mW, Ultra-Small, Audio Power Amplifiers
with Shutdown
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC = 5V, RL= ∞, RIN = RF= 30kΩ, CBIAS = 1µF to GND, SHDN = GND, IN+ = BIAS, TA= TMIN to TMAX, unless otherwise noted.
Typical values are at TA= +25°C.) (Note 3)
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 to GND..............................................................-0.3V to +6V
IN+, IN-, BIAS, SHDN to GND....................-0.3V to (VCC + 0.3V)
Output Short Circuit to VCC or GND (Note 1).............Continuous
Output Short Circuit (OUT+ to OUT-) (Note 1)...........Continuous
Continuous Power Dissipation (TA= +70°C)
8-Bump UCSP (derate 4.7mW/°C above +70°C)..........379mW
8-Pin TDFN (derate 24.4mW°C above +70°C) ...........1951mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Bump Temperature (soldering) (Note 2)
Infrared (15s) ................................................................+220°C
Vapor Phase (60s) ........................................................+215°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Voltage Range VCC Inferred from PSRR test 2.3 5.5 V
Supply Current ICC (Note 4) 2 4.3 mA
Shutdown Supply Current ISHDN SHDN = VCC 35 100 µA
VIH 1.8
SHDN Threshold VIL 0.8 V
SHDN Input Bias Current -400 nA
Common-Mode Bias Voltage VBIAS (Note 5) VCC/2
- 5% VCC/2 VCC/2
+ 5% V
MAX4366, RIN = ∞±5±15
MAX4367, IN- = open ±5±15
Output Offset Voltage VOS
MAX4368, IN- = open ±5 ±7.5 ±15
mV
MAX4366 (open loop) 100 dB
MAX4367 (internally set) 2
Differential Voltage Gain AV(Note 6)
MAX4368 (internally set) 3 V/V
Input Common-Mode Range VCM 0.3 VCC -
1.0 V
Differential Input Resistance RIN
(
DIFF
)
MAX4366, VIN+ - VIN- = 10mV 500 kΩ
Input Resistance VIN- = 0V to VCC (MAX4367/MAX4368) 20 kΩ
TA = +25°C 70 80
Power-Supply Rejection Ratio PSRR VCC = 2.3V to
5.5V TA = TMIN to TMAX 66 dB
Common-Mode Rejection Ratio CMRR 0V ≤ VCM ≤ VCC - 1.0V (MAX4366) 80 dB
2.7V ≤ VCC ≤ 5.5V,
0.6V ≤ VOUT ≤ VCC - 0.6V ±87 ±125
Output Source/Sink Current IOUT (Note 7)
2.3V ≤ VCC ≤ 2.7V,
0.6V ≤ VOUT ≤ VCC - 0.6V ±115
mA
RL = 16Ω60 200
Output Power PO
f = 1kHz,
THD+N <1%
(Note 8) RL = 32Ω120 330
mW
MAX4366/MAX4367/MAX4368
330mW, Ultra-Small, Audio Power Amplifiers
with Shutdown
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 5V, RL= ∞, RIN = RF= 30kΩ, CBIAS = 1µF to GND, SHDN = GND, IN+ = BIAS, TA= TMIN to TMAX, unless otherwise noted.
Typical values are at TA= +25°C.) (Note 3)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
PO = 60mW, RL = 16Ω0.04
Total Harmonic Distortion Plus
Noise THD+N
AV
= - 2V /V , f = 1kH z
( M AX 4366)
(Notes 9 and 10) PO = 120mW, RL = 32Ω0.02 0.15
%
Noise f = 10kHz, referred to input 20 nV/√Hz
To VCC 185
Short-Circuit Current ISC To GND 215 mA
Thermal Shutdown Threshold 165 °C
Thermal Shutdown Hysteresis 10 °C
Power-Up Time tPU 60 ms
Shutdown Time tSHDN 20 ms
Enable Time from Shutdown tENABLE 60 ms
Note 1: Continuous power dissipation must also be observed.
Note 2: This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device
can be exposed to during board-level solder attach and rework. This limit permits only the use of the solder profiles recom-
mended in the industry-standard specification, JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and convection reflow.
Preheating is required. Hand or wave soldering is not allowed.
Note 3: All specifications are 100% tested at TA= +25°C; temperature limits are guaranteed by design.
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: Common-mode bias voltage is the voltage on BIAS and is nominally VCC/2.
Note 6: Differential voltage gain for the MAX4366 is specified as an open-loop parameter because external resistors are used to set
the closed-loop gain. The MAX4367/MAX4368 contain internal feedback resistors that preset the differential voltage gain.
Differential voltage gain is defined as (VOUT+ - VOUT-) / (VIN - VBIAS). All gains are specified over an output voltage range of
0.6V ≤VOUT ≤4.4V.
Note 7: Specification applies to either output. An amplifier peak output current of 87mA is required to support an output load power
of 60mW for a 16Ωload, or 120mW for a 32Ωload.
Note 8: Output power specifications are inferred from the output current test. For 60mW into a 16Ωload, IOUT(PEAK) is 87mA and
VOUT(P-P) is 1.39V per amplifier. For 120mW into a 32Ωload, IOUT(PEAK) is 87mA and VOUT(P-P) is 2.77V per amplifier.
Note 9: Guaranteed by design. Not production tested.
Note 10: Measurement bandwidth for THD+N is 20Hz to 20kHz.
Note 11: Power-up and shutdown times are for the output to reach 90% of full scale with CBIAS = 1µF.
MAX4366/MAX4367/MAX4368
330mW, Ultra-Small, Audio Power Amplifiers
with Shutdown
4 _______________________________________________________________________________________
Typical Operating Characteristics
(Bridge-Tied Load, THD+N Bandwidth = 22Hz to 22kHz, CBIAS = 1µF.)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX4366 toc01
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.01
0.1
1
0.001
10 100k
VCC = 5V
AV = 2V/V
RL = 16Ω
POUT = 10mW
POUT = 60mW
POUT = 25mW
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX4366 toc02
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.01
0.1
1
0.001
10 100k
VCC = 5V
AV = 3V/V
RL = 16Ω
POUT = 10mW
POUT = 60mW
POUT = 25mW
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX4366 toc03
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.01
0.1
1
0.001
10 100k
POUT = 10mW
POUT = 60mW
POUT = 25mW
VCC = 5V
AV = 4V/V
RL = 16Ω
MAX4366 toc04
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.01
0.1
1
0.001
10 100k
POUT = 10mW
POUT = 60mW
POUT = 25mW
VCC = 5V
AV = 20V/V
RL = 16Ω
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX4366 toc05
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.01
0.1
1
0.001
10 100k
POUT = 75mW
POUT = 120mW
POUT = 50mW
VCC = 5V
AV = 2V/V
RL = 32Ω
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX4366 toc06
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.01
0.1
1
0.001
10 100k
POUT = 75mW
POUT = 120mW
POUT = 50mW
VCC = 5V
AV = 3V/V
RL = 32Ω
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX4366 toc07
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.01
0.1
1
0.001
10 100k
POUT = 75mW
POUT = 120mW
POUT = 50mW
VCC = 5V
AV = 4V/V
RL = 32Ω
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX4366 toc08
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.01
0.1
1
0.001
10 100k
POUT = 75mW
VCC = 5V
AV = 20V/V
RL = 32Ω
POUT = 120mW
POUT = 50mW
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX4366 toc09
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.01
0.1
1
0.001
10 100k
POUT = 25mW
POUT = 10mW
POUT = 60mW
VCC = 3V
AV = 2V/V
RL = 16Ω
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX4366/MAX4367/MAX4368
330mW, Ultra-Small, Audio Power Amplifiers
with Shutdown
_______________________________________________________________________________________
5
MAX4366 toc10
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.01
0.1
1
0.001
10 100k
POUT = 25mW
POUT = 10mW
POUT = 60mW
VCC = 3V
AV = 3V/V
RL = 16Ω
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX4366 toc11
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.01
0.1
1
0.001
10 100k
VCC = 3V
AV = 4V/V
RL = 16Ω
POUT = 60mW
POUT = 10mW
POUT = 25mW
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX4366 toc12
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.01
0.1
1
0.001
10 100k
POUT = 60mW
VCC = 3V
AV = 20V/V
RL = 16Ω
POUT = 10mW
POUT = 25mW
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX4366 toc13
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.01
0.1
1
0.001
10 100k
VCC = 3V
AV = 2V/V
RL = 32Ω
POUT = 10mW
POUT = 50mW
POUT = 25mW
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX4366 toc14
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.01
0.1
1
0.001
10 100k
VCC = 3V
AV = 3V/V
RL = 32Ω
POUT = 10mW
POUT = 50mW
POUT = 25mW
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX4366 toc15
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.01
0.1
1
0.001
10 100k
VCC = 3V
AV = 4V/V
RL = 32Ω
POUT = 10mW
POUT = 50mW
POUT = 25mW
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX4366 toc16
FREQUENCY (Hz)
THD+N (%)
10k1k100
0.01
0.1
1
0.001
10 100k
VCC = 3V
AV = 20V/V
RL = 32Ω
POUT = 10mW
POUT = 50mW
POUT = 25mW
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX4366 toc17
OUTPUT POWER (mW)
THD+N (%)
300200100
0.01
0.1
1
10
100
0.001
0 400
VCC = 5V
AV = 2V/V
RL = 16Ω
f = 10kHz
f = 1kHz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
MAX4366 toc18
OUTPUT POWER (mW)
THD+N (%)
300200100
0.01
0.1
1
10
100
0.001
0 400
VCC = 5V
AV = 4V/V
RL = 16Ω
f = 10kHz
f = 1kHz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
Typical Operating Characteristics (continued)
(Bridge-Tied Load, THD+N Bandwidth = 22Hz to 22kHz, CBIAS = 1µF.)
MAX4366/MAX4367/MAX4368
330mW, Ultra-Small, Audio Power Amplifiers
with Shutdown
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(Bridge-Tied Load, THD+N Bandwidth = 22Hz to 22kHz, CBIAS = 1µF.)
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
MAX4366 toc19
OUTPUT POWER (mW)
THD+N (%)
300200100
0.01
0.1
1
10
100
0.001
0 400
VCC = 5V
AV = 2V/V
RL = 32Ω
f = 10kHz
f = 1kHz
MAX4366 toc20
OUTPUT POWER (mW)
THD+N (%)
300200100
0.01
0.1
1
10
100
0.001
0 400
VCC = 5V
AV = 4V/V
RL = 32Ω
f = 10kHz
f = 1kHz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
MAX4366 toc21
OUTPUT POWER (mW)
THD+N (%)
22515075
0.01
0.1
1
10
100
0.001
0 300
f = 10kHz
f = 1kHz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
VCC = 3V
AV = 2V/V
RL = 16Ω
MAX4366 toc22
OUTPUT POWER (mW)
THD+N (%)
22515075
0.01
0.1
1
10
100
0.001
0 300
VCC = 3V
AV = 4V/V
RL = 16Ω
f = 10kHz
f = 1kHz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
MAX4366 toc23
OUTPUT POWER (mW)
THD+N (%)
22515075
0.01
0.1
1
10
100
0.001
0 300
f = 10kHz
f = 1kHz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
VCC = 3V
AV = 2V/V
RL = 32Ω
MAX4366 toc24
OUTPUT POWER (mW)
THD+N (%)
22515075
0.01
0.1
1
10
100
0.001
0 300
VCC = 3V
AV = 4V/V
RL = 32Ω
f = 10kHz
f = 1kHz
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT POWER
OUTPUT POWER vs. SUPPLY VOLTAGE
MAX4366 toc25
SUPPLY VOLTAGE (V)
OUTPUT POWER (mW)
5.04.54.03.53.0
100
200
300
400
500
0
2.5 5.5
THD+N = 10%
THD+N = 1%
RL = 32Ω
OUTPUT POWER vs. SUPPLY VOLTAGE
MAX4366 toc26
SUPPLY VOLTAGE (V)
OUTPUT POWER (mW)
5.04.54.03.53.0
100
200
400
300
500
600
0
2.5 5.5
THD+N = 10%
THD+N = 1%
RL = 16Ω
MAX4366/MAX4367/MAX4368
330mW, Ultra-Small, Audio Power Amplifiers
with Shutdown
_______________________________________________________________________________________
7
OUTPUT POWER vs. LOAD
MAX4366 toc28
LOAD RESISTANCE (Ω)
OUTPUT POWER (mW)
1k10010 10k
50
100
150
200
250
0
THD+N = 10%
AV = 20V/V
THD+N = 1%
AV = 2V/V
VCC = 3V
f = 1kHz
POWER DISSIPATION vs. OUTPUT POWER
MAX4366 toc29
OUTPUT POWER (mW)
POWER DISSIPATION (mW)
15010050
100
200
300
400
500
0
0 200
RL = 16Ω
VCC = 5V
AV = 2V/V
RL = 32Ω
POWER DISSIPATION vs. OUTPUT POWER
MAX4366 toc30
OUTPUT POWER (mW)
POWER DISSIPATION (mW)
50
100
150
200
0
806040200 100
RL = 32Ω
RL = 16Ω
VCC = 3V
AV = 2V/V
POWER DISSIPATION vs. OUTPUT POWER
MAX4366 toc31
OUTPUT POWER (mW)
POWER DISSIPATION (mW)
50
100
150
200
0
40302010050
VCC = 5V
AV = 2V/V
SINGLE ENDED
RL = 16Ω
RL = 32Ω
GAIN AND PHASE vs. FREQUENCY
MAX4366 toc32
FREQUENCY (Hz)
GAIN (dB)/PHASE (deg)
10M1M100k10k1k
-160
-140
-120
-100
-80
-60
-40
-20
0
20
40
60
80
-180
100 100M
VCC = 5V
AV = 1000V/V
SINGLE ENDED
NO LOAD
GAIN
PHASE
Typical Operating Characteristics (continued)
(Bridge-Tied Load, THD+N Bandwidth = 22Hz to 22kHz, CBIAS = 1µF.)
MAX4366/MAX4367/MAX4368
330mW, Ultra-Small, Audio Power Amplifiers
with Shutdown
8 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(Bridge-Tied Load, THD+N Bandwidth = 22Hz to 22kHz, CBIAS = 1µF.)
DIFFERENTIAL POWER-SUPPLY
REJECTION RATIO vs. FREQUENCY
MAX4366 toc33
FREQUENCY (Hz)
PSRR (dB)
100k10k1k10010 1M
-70
-50
-30
-10
0
-80
VCC = 3V
VCC = 5V
-20
-40
-60
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX4366 toc34
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
54321
0.5
1.0
1.5
2.0
2.5
0
0
SUPPLY CURRENT vs. TEMPERATURE
MAX4366 toc35
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
603510-15
0.5
1.0
1.5
2.0
2.5
3.0
0
-40 85
VCC = 5V
VCC = 3V
MAX4366 toc36
SUPPLY VOLTAGE (V)
SHUTDOWN SUPPLY CURRENT (μA)
54321
5
10
15
20
25
30
35
40
45
0
0
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX4366 toc37
TEMPERATURE (°C)
SUPPLY CURRENT (μA)
603510-15
5
10
15
20
25
30
35
40
45
50
0
-40 85
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
VCC = 5V
VCC = 3V
MAX4366/MAX4367/MAX4368
330mW, Ultra-Small, Audio Power Amplifiers
with Shutdown
_______________________________________________________________________________________ 9
Pin Description
PIN/BUMP
TDFN UCSP NAME FUNCTION
1 C3 SHDN Active-High Shutdown. Connect SHDN to GND for normal operation.
2 C1 BIAS DC Bias Bypass. See BIAS Capacitor section for capacitor selection. Connect CBIAS
capacitor from BIAS to GND.
3 A3 IN+ Noninverting Input
4 A1 IN- Inverting Input
5 A2 OUT+ Bridged Amplifier Positive Output
6B3V
CC Power Supply
7 B1 GND Ground
8 C2 OUT- Bridged Amplifier Negative Output
EP — EP Exposed Paddle. Connect exposed pad to GND.
Detailed Description
The MAX4366/MAX4367/MAX4368 bridged audio
power amplifiers can deliver 330mW into a 32Ωload, or
200mW into a 16Ωload, 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
Functional Diagram
). The closed-loop
gain of the input op amp sets the single-ended gain of
the device. Two external resistors set the gain of the
MAX4366 (see
Gain-Setting Resistors
section). The
MAX4367/MAX4368 feature internally fixed gains of
2V/V and 3V/V, respectively. The output of the first
amplifier serves as the input to the second amplifier,
which is configured as an inverting unity-gain follower
in all three devices. This results in two outputs, identical
in magnitude, but 180° out of phase.
BIAS
The MAX4366/MAX4367/MAX4368 feature an internally
generated common-mode bias voltage of VCC/2 refer-
enced to GND. BIAS provides both click-and-pop sup-
pression 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 nonin-
verting input of the other amplifier for proper signal
biasing (
Typical Application Circuit
). Choose the value
of the bypass capacitor as described in the
BIAS
Capacitor
section.
Shutdown
The MAX4366/MAX4367/MAX4368 feature a 35µA, low-
power shutdown mode that reduces quiescent current
consumption and extends battery life. Pulling SHDN
high disables the device’s bias circuitry and drives
OUT+, OUT-, and BIAS to GND. Connect SHDN to
GND for normal operation.
Applications Information
Bridge-Tied Load
The MAX4366/MAX4367/MAX4368 are designed to
drive a load differentially, a configuration referred to as
bridge-tied load (BTL). 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 volt-
age compared to a single-ended amplifier under similar
conditions. The differential gain of the device is twice
the closed-loop gain of the input amplifier. The effective
gain of the MAX4366 is given by:
AR
R
VD F
IN
=×2
+1
RL
OUT+
2 x OUT
OUT-
-1
Figure 1. Bridge-Tied Load Configuration
MAX4366/MAX4367/MAX4368
The effective gains of the MAX4367 and MAX4368 are
AVD = 2V/V and AVD = 3V/V respectively. Substituting 2
x VOUT(P-P) for 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.
Single-Ended Configuration
The MAX4366/MAX4367/MAX4368 can be used as sin-
gle-ended amplifiers (Figure 2). The gain of the device
in single-ended mode is 1/2 the gain in BTL configura-
tion and the output power is reduced by a factor of 4.
The single-ended gains of the MAX4367 and MAX4368
are 1V/V and 1.5V/V, respectively. Set the MAX4366
gain according to the
Gain-Setting Resistors
section.
In single-ended mode, the load must be capacitively
coupled to the device output to block the half-supply
DC voltage from the load (see
Output Coupling
Capacitor
section). Leave the unused output floating.
Power Dissipation
Under normal operating conditions, linear power ampli-
fiers like the MAX4366/MAX4367/MAX4368 can dissi-
pate 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 and TAis the reciprocal of the
derating factor in °C/W as specified in the
Absolute
PTT
DISS MAX
J MAX A
JA
()
()
=-
Θ
VV
PV
R
RMS OUT P P
OUT RMS
L
=
=
−()
22
2
330mW, Ultra-Small, Audio Power Amplifiers
with Shutdown
10 ______________________________________________________________________________________
OUT+
OUT- 8
5
COUT RL
MAX4367
Figure 2. MAX4367 Single-Ended Configuration
VCC
VCC
CIN RIN
RF
CBIAS
6
OUT-
IN+
BIAS
AUDIO INPUT
3
2
CLICKLESS/
POPLESS
SHUTDOWN
CONTROL
GND
SHDN
8
OUT+ 5
7
1
MAX4366
50kΩ
50kΩ
10kΩ
10kΩ
IN-4
Figure 3. MAX4366 Typical Application Circuit
Maximum Ratings
section. For example, ΘJA of a TDFN
package is 41°C/W.
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. If the
power dissipation exceeds the maximum allowed for a
given package, either reduce VCC, increase load
impedance, decrease the ambient temperature, or add
heat sinking to the device. Large output, supply, and
ground traces improve the maximum power dissipation
in the package.
Thermal overload protection limits total power dissipa-
tion in the MAX4366/MAX4367/MAX4368. When the
junction temperature exceeds +165°C, the thermal pro-
tection circuitry disables the amplifier output stage. The
amplifiers are re-enabled once the junction temperature
cools by +10°C. This results in a pulsing output under
continuous thermal overload conditions avoiding dam-
age to the part.
Component Selection
Gain-Setting Resistors
External feedback components set the gain of the
MAX4366. Resistors RFand RIN (Figure 3) set the gain
of the input amplifier as follows:
The gain of the device in a single-ended configuration
is half the gain of the BTL case. Choose RFbetween
10kΩand 50kΩ. The gains of the MAX4367/MAX4368
are set internally (Figure 4).
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:
fRC
dB IN IN
-3
1
2
=π
AR
R
VD F
IN
=⎛
⎝
⎜⎞
⎠
⎟
2
MAX4366/MAX4367/MAX4368
330mW, Ultra-Small, Audio Power Amplifiers
with Shutdown
______________________________________________________________________________________ 11
Figure 4. MAX4367/MAX4368 Typical Application Circuit
VCC
VCC
CIN RIN
RF
CBIAS
6
OUT-
IN+
BIAS
AUDIO
INPUT
3
2
CLICKLESS/
POPLESS
SHUTDOWN
CONTROL
GND
SHDN
8
OUT+ 5
7
1
MAX4367
MAX4368
50kΩ
50kΩ
10kΩ
10kΩ
IN-4
MAX4367: RIN = RF = 20kΩ
MAX4368: RIN = 20kΩ, RF = 30kΩ
PIN NUMBERS REFER TO TDFN PACKAGE.
MAX4366/MAX4367/MAX4368
Choose RIN according to the
Gain-Setting Resistors
section. Choose the 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 system.
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 power-
supply rejection ratio 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 suppression, ensure that the
input capacitor (CIN) is fully charged (ten time con-
stants) before CBIAS. The value of CBIAS for best click-
and-pop suppression is given by:
In addition, a larger CBIAS value yields higher PSRR,
especially in single-ended applications.
Output-Coupling Capacitor
The MAX4366/MAX4367/MAX4368 require output-cou-
pling capacitors only when configured as a single-
ended amplifier. The output capacitor blocks the DC
component of the amplifier output, preventing DC cur-
rent flowing to the load. The output capacitor and the
load impedance form a highpass filter with the -3dB
point determined by:
As with the input capacitor, choose the output capacitor
(COUT) such that f-3dB is well below the lowest frequen-
cy of interest. Setting f-3dB too high affects the low-
frequency response of the system.
In addition to click-and-pop suppression and frequency
band considerations, the load impedance is another
concern when choosing COUT. Load impedance can
vary, changing the -3dB point of the output filter. A
lower impedance increases the corner frequency,
degrading low-frequency response. Select COUT such
that the worst-case load/COUT combination yields an
adequate response.
Clickless/Popless Operation
Proper selection of AC-coupling capacitors 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, improving click-and-pop suppression.
Supply Bypassing
Proper supply bypassing ensures low-noise, low-distor-
tion performance. Place a 0.1µF ceramic capacitor in par-
allel with a 10µF capacitor from VCC to GND. Locate the
bypass capacitors as close to the device as possible.
Headphone Applications
The MAX4366/MAX4368 can drive a mono headphone
when configured as a single-ended amplifier. Typical 2-
wire headphone plugs consist of a tip and sleeve. The tip
is the signal carrier while the sleeve is the ground con-
nection (Figure 5). Figure 6 shows the device configured
to drive headphones. OUT+ is connected to the tip,
delivering the signal to the headphone, while OUT-
remains unconnected.
fRC
dB L OUT
-3
1
2
=π
CCR
k
BIAS IN IN
≤Ω
⎡
⎣
⎢⎤
⎦
⎥
10 25
330mW, Ultra-Small, Audio Power Amplifiers
with Shutdown
12 ______________________________________________________________________________________
Figure 5. Typical 2-Wire Headphone Plug
TIP
(SIGNAL)
SLEEVE
(GND)
Wireless-Phone Headset Application
Many wireless telephones feature an earbud speaker/in-
line microphone combination for hands-free use. One
common solution is to use a BTL amplifier that drives the
internal speaker and an earplug jack that mutes the inter-
nal speaker by physically disconnecting OUT- when a
headset is plugged in (Figure 7). The headset is driven
single-endedly, requiring an output-coupling capacitor,
COUT, and resulting in a 4x reduction in output power.
Adding Volume Control
The addition of a digital potentiometer provides simple
volume control. Figure 8 shows the MAX4367/MAX4368
with the MAX5160 digital potentiometer used as an
input attenuator. Connect the high terminal of the
MAX5160 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.
Use the 100kΩversion of the MAX5160.
Layout Considerations
Good layout improves performance by decreasing the
amount of stray capacitance and noise at the amplifi-
er’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.
UCSP Considerations
For general UCSP information and PC layout considera-
tions, please refer to the Maxim Application Note:
UCSP–A
Wafer-Level Chip-Scale Package.
MAX4366/MAX4367/MAX4368
330mW, Ultra-Small, Audio Power Amplifiers
with Shutdown
______________________________________________________________________________________ 13
OUT+ HEADPHONE JACK
OUT- 8
5
COUT
MAX4366
MAX4367
MAX4368
Figure 6. MAX4367 Headphone Application Circuit
EARBUD SPEAKER
JACK
INTERNAL
LOUDSPEAKER
COUT
OUT+
OUT-
MAX4366
MAX4367
MAX4368
Figure 7. Headset with Internal Speaker Application Circuit
OUT+
AUDIO
INPUT
OUT-
IN-
3H
W5 4
5
8
CIN
6L
MAX4367
MAX4368
MAX5160
Figure 8. MAX4367/MAX5160 Volume Control Circuit
Ordering Information (continued)
PART
TEMP RANGE
PIN/BUMP-
PACKAGE
TOP
MARK
MAX4367EBL-T
-40°C to +85°C
8 UCSP AAL
MAX4367ETA+T
-40°C to +85°C
8 TD FN - E P *
+AGA
MAX4368EBL-T
-40°C to +85°C
8 UCSP
AAM
MAX4368ETA+T
-40°C to +85°C
8 TD FN - E P *
+AGB
MAX4366/MAX4367/MAX4368
330mW, Ultra-Small, Audio Power Amplifiers
with Shutdown
14 ______________________________________________________________________________________
*EXPOSED PAD.
CONNECT TO GND.
TOP VIEW
VCC
OUT+
IN-
12
OUT-
GND
BIAS
IN+
SHDN
TDFN
(3mm x 3mm x 0.8mm)
34
MAX4366
MAX4367
MAX4368
876
5
+
Pin Configurations (continued)
PART GAIN
MAX4366 External
MAX4367 2V/V
MAX4368 3V/V
Selector Guide
*
EP = Exposed paddle.
+
Denotes lead-free package.
MAX4366/MAX4367/MAX4368
VCC
OUT-
IN+
BIAS
CLICKLESS/
POPLESS
SHUTDOWN
CONTROL
GND
SHDN
OUT+
MAX4366
50kΩ
50kΩ
10kΩ
10kΩ
IN-
VCC
OUT-
IN+
BIAS
CLICKLESS/
POPLESS
SHUTDOWN
CONTROL
GND
SHDN
OUT+
MAX4367
MAX4368
50kΩ
50kΩ
10kΩ
10kΩ
IN-
*RF = 30kΩ (MAX4368)
RF = 20kΩ (MAX4367)
RF*
20kΩ
Chip Information
TRANSISTOR COUNT: 669
PROCESS: BiPOLAR
330mW, Ultra-Small, Audio Power Amplifiers
with Shutdown
______________________________________________________________________________________ 15
Functional Diagrams
Package Information
For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages.
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
8 TDFN T833-2 21-0137
8 UCSP B9-2 21-0093
MAX4366/MAX4367/MAX4368
330mW, Ultra-Small, Audio Power Amplifiers
with Shutdown
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
5 6/08 Removed SOT23 and µMAX packages 1, 2, 9, 11, 14
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 ____________________
16
© 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.