PAM8403
Filterless 3W Class-D Stereo Audio Amplifier
Key Features

General Description

n 3W Output at 10% THD with a 4 Ω Load and
5V Power Supplyn Filterless, Low Quiescent Current and Low
EMIn Low THD+N
n Superior Low Noisen Efficiency up to 90%
n Short Circuit Protectionn Thermal Shutdown
n Few External Components to Save theSpace and Costn Pb-Free Package

The PAM8403 is a 3W, class-D audio amplifier. Itoffers low THD+N, allowing it to achieve highquality sound reproduction. The new filterlessarchitecture allows the device to drive the speakerdirectly, requiring no low-pass output filters,thusto save the system cost and PCB area.
With the same numbers of external components,
the efficiency of the PAM8403 is much better thanthat of class-AB cousins. It can extend the battery
life, ideal for portable applications.
The PAM8403 is available in SOP-16 package.

Applications
nnnnn

LCD Monitors / TV Projectors
Notebook Computers
Portable Speakers
Portable DVD Players, Game Machines
Cellular Phones/Speaker Phones

Typical Application
Efficiency vs Output Power
100901μF

470μF

1μF

6VDD
0.47μF

80

PVDDEfficiency(%)

VDD

1μF
134

PVDD PVDD

7INL+OUT_L

VREF-OUT_L

RL=4Ω60
5040301010080.1μF

PAM84030.47μF
10INRRi
12SHDN
5MUTE-OUT_R

INR
SHDN+OUT_R

3142

11.5

22.53

Radiated Emissions

16FCC Class B Limit

GND NC PGNDPGND
90.5

Output Pow er(W)

MUTE
11RL=8Ω20Ri

INL

7015

Power Analog Microelectronics , Incwww.poweranalog.com

09/2008 Rev 1.31PAM8403
Filterless 3W Class-D Stereo Audio Amplifier
Block Diagram
VDD

PVDD

PGNDVDD/2+-INR+OUT_RDRIVER-OUT_R

MODULATOR

SHDN

ATTENUATION DECODER

INTERFACE CONTROL

MUTE

THERMAL
PROTECTION

INTERNAL
OSCILLATOR

BIAS ANDREFERENCES

VREF

OSC
CURRENTPROTECTION

MODULATORINL+OUT_LDRIVER+-OUT_L

VDD/2

GND

PVDD

PGND

Pin Configuration & Marking Information
Top View
SOP-1611621545

PAM8403
XATYWWLL

3X: Internal Code
A: Assembly Code
T: Testing Code
Y: Year
WW: Week
LL: Internal Code14131261171089Power Analog Microelectronics , Incwww.poweranalog.com

09/2008 Rev 1.32PAM8403
Filterless 3W Class-D Stereo Audio Amplifier
Pin Descriptions
Pin Number

Pin Name

Description

1+OUT_L

Left Channel Positive Output

2PGND

Power GND

3-OUT_L

Left Channel Negative Output

4PVDD

Power VDD

5MUTE

Mute Control Input（active low）

6

VDD

Analog VDD

7INL

Left Channel Input

8

VREF

Internal analog reference, connect a bypass capacitor from VREF to GND

9NC

No connect

10INR

Right Channel Input

11GND

Analog GND

12SHDN

Shutdown Control Input (active low)

13

PVDD

Power VDD

14-OUT_R

Right Channel Negative Output

15PGNDPower GND

16+OUT_R

Right Channel Positive Output

Absolute Maximum Ratings

These are stress ratings only and functional operation is not implied . Exposure to absolutemaximum ratings for prolonged time periods may affect device reliability . All voltages are withrespect to ground .
Supply Voltage . ...........................................6.6V
Input Voltage.............................-0.3V to V DD+0.3V
Operation Temperature Range.........-40°C to 85 °C
Maximum Junction Temperature..................150°C

Operation Junction Temperature.....-40 °C to 125 °C
Storage Temperature.....................-65 °C to 150 °C
Soldering Temperature....................... 300°C, 5sec

Recommended Operating Conditions
Supply voltage Range........................ 2.5V to 5.5V
Max. Supply Voltage (for Max. duration of30 minutes)................................................6.4V

Operation Temperature Range.........-40 °C to 85 °C
Junction Temperature Range.........-40 °C to 125 °C

Thermal Information
Parameter

Symbol

Package

Maximum

Unit

Thermal Resistance (Junction to Ambient)

θJA

SOP-16

110°C/W

Thermal Resistance (Junction to Case)

θJC

SOP-1623°C/W

Power Analog Microelectronics , Incwww.poweranalog.com

09/2008 Rev 1.33PAM8403
Filterless 3W Class-D Stereo Audio AmplifierElectrical Characteristic
V DD=5V, Gain=24dB, R L=8 Ω , T A=25 °C , unless otherwise noted.
SymbolParameter

VIN

Supply Power

Test Conditions

THD+N=1%,f=1kHz, RL =4 Ω
Output Power
THD+N=10%,f=1kHz, RL =8 Ω

THD+N=1%,f=1kHz, RL =8 Ω

VDD=5.0V,Po=0.5W,RL=8 Ω
THD+N

Total Harmonic Distortion Plus

VDD=3.6V,Po=0.5W,RL=8 ΩNoiseVD D=5.0V,Po=1W,RL =4 Ω
VD D=3.6V,Po=1W,RL =4 ΩGvGain

PSRR

Power Supply Ripple Rejection

TYP

2.5

THD+N=10%,f=1kHz, RL =4 ΩPo

MIN

5.5

VDD=5.0V

3.2

VDD=3.6V

1.6

VDD=3.0V

1.3

VDD=5.0V

2.5

VDD=3.6V

1.3

VDD=3.0V

0.85

VDD=5.0V

1.8

VDD=3.6V

0.9

VDD=3.0V

0.6

VDD=5.0V

1.4

VDD=3.6V

0.72

VDD=3.0V

0.45

f=1kHzMAX UNIT

0.15

V

W

W

W

W%

0.11
f=1kHz

0.15
0.11
24

VD D=5.0V, Inputs ac-grounded with

f=100Hz-59

CIN =0.47μF

f=1kHz-58%
dB
dBCs

Crosstalk

VDD=5V,Po=0.5W,RL =8Ω,Gv=20dB

F=1kHz

-95

dB

SNR

Signal-to-noise ratio

VDD=5V, Vorms=1V,Gv=20dB

f=1kHz80dB

Vn

Output noise

VDD=5V, Inputs ac-grounded with

A-weighting

100

CIN =0.47μF

No A-weighting

150

VDD=5.0V, THD=1%

f=1kHz90

Dyn

Dynamic rangeη

Efficiency

R L=8Ω, THD=10%
R L=4Ω, THD=10%

f=1kHz

VDD=5.0V
IQ

Quiescent Current

VDD=3.6V
VDD=3.0V

8783μVdB%

16No load

10mA

8Power Analog Microelectronics , Incwww.poweranalog.com

09/2008 Rev 1.34PAM8403
Filterless 3W Class-D Stereo Audio AmplifierElectrical Characteristic (Continued)
V DD=5V Gain=24dB, R L=8 Ω , T A=25 °C , unless otherwise noted.
SymbolParameter

IMUT E

Muting Current

VDD=5.0V

VMUTE =0.3V

3.5mA

ISD

Shutdown Current

VDD=2.5V to 5.5V

Vsd=0.3V

<1μA

PMOS

180

NMOS

140

Rdson

Static Drain-to-source On-state
Resistor

Test Conditions

IDS =500mA,Vgs=5V

MIN

TYP

MAXUNITmΩfsw

Switching Frequency

VDD=3V to 5V

260kHzVos

Output Offset Voltage

Vin=0V, VDD=5V

10mV

VIH

Enable Input High Voltage

VDD=5.0V

VIL

Enable Input Low Voltage

VDD=5.0V

VIH

MUTE Input High Voltage

VDD=5.0V

VIL

MUTE Input Low Voltage

VDD=5.0V

OTP

Over Temperature Protection

OTH

Over Temperature Hysterisis

No Load, Junction Temperature

1.5

1.40.71.5

1.40.7

VDD=5V

0.4

140300.4

VV°C

Power Analog Microelectronics , Incwww.poweranalog.com

09/2008 Rev 1.35PAM8403
Filterless 3W Class-D Stereo Audio Amplifier
Typical Operating Characteristics (T =25°C)
A

2. THD+N vs Output Power

1. THD+N vs Output Power
1001005050

V DD=3.3V201010V DD=2.5V

552%

2%

110.5

0.5

0.2

0.2

0.1

0.1

0.05

0.05

V DD=5V

0.02
0.01
20m

50m

100m

200m

500m

12

V DD=5V

0.02
0.01
20m

450m

100m

200m

500m

124W

W

R L=4 Ω , Gain = 24dB, f=1kHz

R L=8 Ω , Gain = 24dB, f=1kHz

3. THD+N vs Frequency

4. THD+N vs Frequency

100

100505020201010552%

V DD=3.3V

V DD=2.5V2021%

0.5

10.5

L0.20.20.1

0.1

0.05

0.050.02

L0.02

0.01
20R50

1002005001k2k5k10k0.01
2020kHzR
50

1002005001k2k5k10k20k

HzV DD=5V, R L=8 Ω ,Gain = 24dB, Cin=1 μ F

V DD=5V, R L=4 Ω ,Gain = 24dB, Cin=1 μ F

Power Analog Microelectronics , Incwww.poweranalog.com

09/2008 Rev 1.36

PAM8403
Filterless 3W Class-D Stereo Audio Amplifier
Typical Operating Characteristics (continued)
5. Frequency response

6. Crosstalk VS Frequency+0+24.4LT
TTTTTTTT
TTT-10+24.2-20+24-30+23.8dBrR-40+23.6-50dB+23.4-60

A+23.2-70+23-80

L-90+22.8-100

R+22.6102050

100

200

500

1k2k5k

10k-110
2020k

50

100

200

500

1k2k

5k

10k

20k

HzHz

V DD=5V, R L=4 Ω , Gv=24dB, Po=0.5W

V DD=5V, R L=8 Ω ,Gain = 24dB, Cin=1 μ F

7. Noise Floor FFTdB
V+0+0-10-10-20-20-30-30-40-40-50-50-60-60-70-80-70L-80-90-90-100-100-110-12020dBV-110R50100

2005001k2k5k10k20k-120HzInputs ac-ground, V DD=5V, R L=8 Ω ,Cin=1 μ F

Power Analog Microelectronics , Incwww.poweranalog.com

09/2008 Rev 1.37PAM8403
Filterless 3W Class-D Stereo Audio Amplifierprobably damage the device. Therefore, it'srecommended to use either 4 Ni-MH (NickelMetal Hydride) rechargeable batteries or 3 dry or
alkaline batteries.

Application Notes
1. When the PAM8403 works with LC filters, itshould be connected with the speaker before it's
powered on, otherwise it will be damaged easily.

4. One should not make the input signal toolarge. Large signal can cause the clipping ofoutput signal when increasing the volume. This
will damage the device b ecause of big gain of thePAM8403 .

2. When the PAM8403 works without LC filters,
it's better to add a ferrite chip bead at theoutgoing line of speaker for suppressing thepossible electromagnetic interference.

5. When testing the PAM8403 without LC filters
by using resistor instead of speaker as the output
load, the test results, e.g. THD or efficiency, will
be worse than those of using speaker as load.

3. The recommended operating voltage is5.5V. When the PAM8403 is powered with 4battery cells, it should be noted that the voltageof 4 new dry or alkaline batteries is over 6.0V,
higher than its operation voltage, which will

Test Setup for Performance Testing
PAM8403 Demo BoardLoad+OUT
AP System One
Generator

Input

APLow PassFilter

GND-OUTAP System One
Analyzer

AUX-0025

VDD

Power SupplyNotes
1. The AP AUX-0025 low pass filter is necessary for class-D amplifier measurement with AP analyzer.
2. Two 22µH inductors are used in series with load resistor to emulate the small speaker for efficiency
measurement.

Power Analog Microelectronics , Incwww.poweranalog.com

09/2008 Rev 1.38

PAM8403
Filterless 3W Class-D Stereo Audio Amplifier
Application Information
Maximum Gain

resistance (ESR) ceramic capacitor, typically
1.0μF, works best, placing it as close as possible
to the device V DD terminal. For filtering lowerfrequency noise signals, a large capacitor of20μF (ceramic) or greater is recommended,
placing it near the audio power amplifier.

As shown in block diagram (page 2), thePAM8403 has two internal amplifier stages. The
first stage's gain is externally con figurable, while
the second stage's is internally fixed. The
closed-loop gain of the first stage is set by
selecting the ratio of R f to R i while the second
stage's gain is fixed at 2x.The output of amplifier
1 serves as the input to amplifier 2, thus the two
amplifiers produce signals identical inmagnitude, but different in phase by 180°.
Consequently, the differential gain for the IC isInput Capacitor (C i)
Large input capacitors are both expensive andspace hungry for portable designs. Clearly, acertain sized capacitor is needed to couple in low
frequencies without severe attenu ation. But inmany cases the speakers used in portablesystems, whether internal or external, have little
ability to reproduce signals below 100Hz to150Hz. Thus, using a large input capacitor may
not increase actual system perfor mance. In thiscase, input capacitor (C i) and input resistance(R i) of the amplifier form a high-pass filter withthe corner frequency determined by equation
below,
1fC=2πRiCi

A VD=20*log [2*(R f/R i)]
T h e PA M 8 4 0 3 s e t s m a x i m u m R f = 1 4 2 k Ω ,minimum R i=18k Ω , so the maximum closed-gain
is 24dB.
Mute Operation
The MUTE pin is an input for controlling theoutput state of the PAM8403. A logic low on thispin disables the outputs, and a logic high on thispin enables the outputs. This pin may be used asa quick disable or enable of the outputs without avolume fade. Quiescent current is listed in theelectrical characteristic table. The MUTE pin canbe left floating due to the internal pull-up.

In addition to system cost and size, click and pop
perfor mance is affected by the size of the input
coupling capacitor, C i. A larger input coupling
capacitor requires more charge to reach its
quiescent DC voltage (nominally 1/2 V DD). Thischarge comes from the internal circuit via thefeedback and is apt to create pops upon device
enable. Thus, by minimizing the capacitor sizebased on necessary low frequency response,
turn-on pops can be minimized.

Shutdown operation
In order to reduce power consumption while notin use, the PAM8403 contains shutdown circuitry
to turn off the amplifier's bias circuitry. This
shutdown feature turns the amplifier off when
logic low is applied to the SHDN pin. By switching
the SHDN pin connected to GND, the PAM8403
supply current draw will be minimized in idle
mode. The SHDN pin can be left floating due tothe internal pull-up.

Analog Reference Bypass Capacitor (C BYP)The Analog Reference Bypass Capacitor (C BYP) is
the most critical capacitor and serves several
important functions. During start-up or recovery
from shutdown mode, C BYP determines the rate at
which the amplifier starts up. The second
function is to reduce noise caused by the power
supply coupling into the output drive signal. This
noise is from the internal analog reference to theamplifier, which appears as degraded PSRR andTHD+N.

Power supply decoupling
The PAM8403 is a high performance CMOS
audio amplifier that requires adequate power
supply decoupling to ensure the output THD andPSRR as low as possible. Power supply
decoupling affects low frequency response.
Optimum decoupling is achieved by using twocapacitors of different types targeting to different
types of noise on the power supply leads. For
higher frequency transients, spikes, or digitalhash on the line, a good low equivalent-series-

A ceramic bypass capacitor (C BYP) with values of
0.47μF to 1.0μF is recommended for the best
THD and noise performance. Increasing thebypass capacitor reduces clicking and popping
noise from power on/off and entering and leaving
shutdown.

Power Analog Microelectronics , Incwww.poweranalog.com

09/2008 Rev 1.39PAM8403
Filterless 3W Class-D Stereo Audio Amplifier
How to Reduce EMI (Electro MagneticInterference)

Under Voltage Lock-out (UVLO)The PAM8403 incorporates circuitry designed todetect low supply voltage. When the supply
voltage drops to 2.0V or below, the PAM8403
outputs are disabled, and the device comes out of
this state and starts to normal function when V DD
≥2.2V.

A simple solution is to put an additional capacitor
1000 μ F at power supply terminal for power line
coupling if the traces from amplifier to speakers
are short (<20cm).
Most applications require a ferrite bead filter asshown in Figure 2. The ferrite filter reduces EMI ofaround 1 MHz and higher. When selecting aferrite bead, choose one with high impedance athigh frequencies, and low impedance at low
frequencies.

Short Circuit Protection (SCP)
The PAM8403 has short circuit protection
circuitry on the outputs to prevent damage to thedevice when output-to-output or output-to-GND
short occurs. When a short circuit is detected on
the outputs, the outputs are disabled
immediately. If the short was removed, the device
activates again.

Ferrite Bead

OUT+Over Temperature Protection

220pF
Ferrite Bead

Thermal protection on the PAM8403 prevents thedevice from damage when the internal die
temperature exceeds 140°C. There is a 15 degree
tolerance on this trip point from device to device.
Once the die temperature exceeds the thermal
set point, the device outputs are disabled. This is
not a latched fault. The thermal fault is cleared
once the temperature of the die is reduced by
30 °C . This large hysteresis will prevent motor
boating sound well and the device begins normal
operation at this point without external systemintervention.

OUT220pF

Figure 2: Ferrite Bead Filter to reduce EMI

Power Analog Microelectronics , Incwww.poweranalog.com

09/2008 Rev 1.3

10

PAM8403
Filterless 3W Class-D Stereo Audio Amplifier
Ordering Information

PAM8403 X X
Shipping Package
Package TypePart Number
PAM8403DR

Marking

Package Type

MOQ/Shipping Package

SOP-162,500 Units/Tape&Reel

PAM8403
XATYWWLL

Power Analog Microelectronics , Incwww.poweranalog.com

09/2008 Rev 1.311

PAM8403
Filterless 3W Class-D Stereo Audio Amplifier
Outline Dimension

A1A

A2

SOP-16B
DEE1LCθeSymbol

Dimensions Millimeters
MinMax

A

1.350

1.750

A1

0.100

0.250

A2

1.350

1.550

B

0.330

0.510

C

0.190

0.250

D

9.800

10.000

E

3.800

4.000

E1

5.800

6.300

e1.270(TYP)

L

0.400

1.270

θ

0º8º

Power Analog Microelectronics , Incwww.poweranalog.com

09/2008 Rev 1.312