November 1, 2007
LM4673
Filterless, 2.65W, Mono, Class D Audio Power Amplifier
General Description
The LM4673 is a single supply, high efficiency, 2.65W, mono,
Class D audio amplifier. A low noise, filterless PWM architec-
ture eliminates the output filter, reducing external component
count, board area consumption, system cost, and simplifying
design.
The LM4673 is designed to meet the demands of mobile
phones and other portable communication devices. Operat-
ing on a single 5V supply, it is capable of driving a 4Ω speaker
load at a continuous average output of 2.1W with less than
1% THD+N. Its flexible power supply requirements allow op-
eration from 2.4V to 5.5V.
The LM4673 has high efficiency with speaker loads compared
to a typical Class AB amplifier. With a 3.6V supply driving an
8Ω speaker, the IC's efficiency for a 100mW power level is
80%, reaching 88% at 400mW output power.
The LM4673 features a low-power consumption shutdown
mode. Shutdown may be enabled by driving the Shutdown
pin to a logic low (GND).
The gain of the LM4673 is externally configurable which al-
lows independent gain control from multiple sources by sum-
ming the signals. Output short circuit and thermal overload
protection prevent the device from damage during fault con-
ditions.
Key Specifications
■
Efficiency at 3.6V, 400mW into 8Ω speaker 88% (typ)
■
Efficiency at 3.6V, 100mW into 8Ω speaker 80% (typ)
■
Efficiency at 5V, 1W into 8Ω speaker 86% (typ)
■ Quiescent current, 3.6V supply 2.1mA (typ)
■
Total shutdown power supply current 0.01µA (typ)
■ Single supply range 2.4V to 5.5V
■ PSRR, f = 217Hz 78dB
Features
■Mono Class D Operation
■No output filter required for inductive loads
■Externally configurable gain
■Very fast turn on time: 17μs (typ)
■Minimum external components
■"Click and pop" suppression circuitry
■Micro-power shutdown mode
■Available in space-saving 0.4mm pitch micro SMD and
LLPTm packages
Applications
■Mobile phones
■PDAs
■Portable electronic devices
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2007 National Semiconductor Corporation 201522 www.national.com
LM4673 Filterless, 2.65W, Mono, Class D Audio Power Amplifier
Typical Application
201522j3
FIGURE 1. Typical Audio Amplifier Application Circuit
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LM4673
Connection Diagrams
9 Bump micro SMD Package
20152236
Top View
Order Number LM4673TM
See NS Package Number TMD09GGA
micro SMD Marking
20152257
Top View
X — Date Code
T— Die Traceability
G — Boomer Family
G4 — LM4673TM
Leadless Leadframe Package (LLP)
20152201
Top View
Order Number LM4673SD
See NS Package Number SDA08A
Contact NSC Sales Office for Availability
LLP Marking
20152202
Top View
Z — Plant Code
XY — Date Code
TT — Die Traceability
L4673 — LM4673SD
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LM4673
Absolute Maximum Ratings (Notes 1, 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (Note 1) 6.0V
Storage Temperature −65°C to +150°C
Voltage at Any Input Pin VDD + 0.3V ≥ V ≥ GND - 0.3V
Power Dissipation (Note 3) Internally Limited
ESD Susceptibility, all other pins (Note 4) 2.0kV
ESD Susceptibility (Note 5) 200V
Junction Temperature (TJMAX)150°C
Thermal Resistance
θJA (micro SMD) 99.1°C/W
θJA (LLP) 73°C/W
Soldering Information
See AN-1112 "microSMD Wafers Level Chip Scale
Package."
Operating Ratings (Notes 1, 2)
Temperature Range
TMIN ≤ TA ≤ TMAX −40°C ≤ TA ≤ 85°C
Supply Voltage 2.4V ≤ VDD ≤ 5.5V
Electrical Characteristics (Notes 1, 2)
The following specifications apply for AV = 2V/V (RI = 150kΩ), RL = 15µH + 8Ω + 15µH unless otherwise specified. Limits apply for
TA = 25°C.
Symbol Parameter Conditions
LM4673 Units
(Limits)
Typical Limit
(Note 6) (Notes 7, 8)
|VOS|Differential Output Offset Voltage VI = 0V, AV = 2V/V,
VDD = 2.4V to 5.0V 5 mV (max)
|IIH| Logic High Input Current VDD = 5.0V, VI = 5.5V 17 100 μA (max)
|IIL| Logic Low Input Current VDD = 5.0V, VI = –0.3V 0.9 5 μA (max)
VIN = 0V, No Load, VDD = 5.0V 2.6 3.75 mA (max)
IDD Quiescent Power Supply Current
VIN = 0V, No Load, VDD = 3.6V 2.1 2.9 mA
VIN = 0V, No Load, VDD = 2.4V 1.7 2.3 mA (max)
VIN = 0V, RL = 8Ω, VDD = 5.0V 2.6
VIN = 0V, RL = 8Ω, VDD = 3.6V 2.1
VIN = 0V, RL = 8Ω, VDD = 2.4V 1.7
ISD Shutdown Current VSHUTDOWN = 0V
VDD = 2.4V to 5.0V 0.01 1 μA (max)
VSDIH Shutdown voltage input high 1.4 V (min)
VSDIL Shutdown voltage input low 0.4 V (max)
ROSD Output Impedance VSHUTDOWN = 0.4V 100 kΩ
AVGain 300kΩ/RI
270kΩ/RI
330kΩ/RI
V/V (min)
V/V (max)
RSD
Resistance from Shutdown Pin to
GND
300 kΩ
POOutput Power
RL = 15μH + 4Ω + 15μH
THD = 10% (max)
f = 1kHz, 22kHz BW
VDD = 5V
VDD = 3.6V
VDD = 2.5V
2.65
1.3
550
W
W
mW
RL = 15μH + 4Ω + 15μH
THD = 1% (max)
f = 1kHz, 22kHz BW
VDD = 5V
VDD = 3.6V
VDD = 2.5V
2.15
1.06
450
W
W
mW
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LM4673
Symbol Parameter Conditions
LM4673 Units
(Limits)
Typical Limit
(Note 6) (Notes 7, 8)
POOutput Power
RL = 15μH + 8Ω + 15μH
THD = 10% (max)
f = 1kHz, 22kHz BW
VDD = 5V 1.7 W
VDD = 3.6V 870 mW
VDD = 2.5V 350 mW
RL = 15μH + 8Ω + 15μH
THD = 1% (max)
f = 1kHz, 22kHz BW
VDD = 5V 1.24 W
VDD = 3.6V 650 600 mW
VDD = 2.5V 300 mW
THD+N Total Harmonic Distortion + Noise
VDD = 5V, PO = 0.1W, f = 1kHz 0.03 %
VDD = 3.6V, PO = 0.1W, f = 1kHz 0.02 %
VDD = 2.5V, PO = 0.1W, f = 1kHz 0.02 %
PSRR Power Supply Rejection Ratio
(Input Referred)
VRipple = 200mVPP Sine,
fRipple = 217Hz, VDD = 3.6, 5V
Inputs to AC GND, CI = 2μF
78
dB
VRipple = 200mVPP Sine,
fRipple = 1kHz, VDD = 3.6, 5V
Inputs to AC GND, CI = 2μF
72
dB
SNR Signal to Noise Ratio VDD = 5V, PO = 1WRMS 97 dB
εOUT
Output Noise
(Input Referred)
VDD = 3.6V, f = 20Hz – 20kHz
Inputs to AC GND, CI = 2μF
No Weighting
30
μVRMS
VDD = 3.6V, Inputs to AC GND
CI = 2μF, A Weighted 23 μVRMS
CMRR Common Mode Rejection Ratio
(Input Referred)
VDD = 3.6V, VRipple = 1VPP Sine
fRipple = 217Hz 70 dB
TWU Wake-up Time VDD = 3.6V 17 μs
TSD Shutdown Time 140 μs
ηEfficiency
VDD = 3.6V, POUT = 400mW
RL = 8Ω 88 %
VDD = 5V, POUT = 1W
RL = 8Ω 86 %
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LM4673
Note 1: All voltages are measured with respect to the ground pin, unless otherwise specified.
Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions
which guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters
where no limit is given, however, the typical value is a good indication of device performance.
Note 3: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX, θJA, and the ambient temperature TA. The maximum
allowable power dissipation is PDMAX = (TJMAX–TA)/θJA or the number given in Absolute Maximum Ratings, whichever is lower. For the LM4673, TJMAX = 150°C.
The typical θJA is 99.1°C/W for the micro SMD package.
Note 4: Human body model, 100pF discharged through a 1.5kΩ resistor.
Note 5: Machine Model, 220pF – 240pF discharged through all pins.
Note 6: Typical specifications are specified at 25°C and represent the parametric norm.
Note 7: Tested limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
