LM4671 Datasheet, PDF (1/18 Pages) National Semiconductor (TI) – Filterless High Efficiency 2.5W Switching Audio Amplifier

March 2005
LM4671
Filterless High Efficiency 2.5W Switching Audio
Amplifier
General Description
The LM4671 is a single supply, high efficiency 2.5W switch-
ing audio amplifier. A low noise, filterless PWM architecture
eliminates the output filter, reducing external component
count, board area consumption, system cost, and simplifying
design.
The LM4671 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 operation from 2.4V to 5.5V.
The LM4671 has high efficiency with speaker loads com-
pared to a typical Class AB amplifier. With a 3V supply
driving an 8Ω speaker, the IC’s efficiency for a 100mW
power level is 80%, reaching 88% at 400mW output power.
The LM4671 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 LM4671 is externally configurable which
allows independent gain control from multiple sources by
summing the signals.
Key Specifications
j Efficiency at 3.6V, 100mW into 8Ω speaker 80% (typ)
j Efficiency at 3.6V, 400mW into 8Ω speaker 88% (typ)
j Efficiency at 5V, 1W into 8Ω speakerr
86% (typ)
j Quiescent current, 3.6V supply
2.8mA (typ)
j Total shutdown power supply current 0.01µA (typ)
j Single supply range
2.4V to 5.5V
Features
n No output filter required for inductive loads
n Externally configurable gain
n Very fast turn on time: 1ms (typ)
n Minimum external components
n "Click and pop" suppression circuitry
n Micro-power shutdown mode
n Available in space-saving microSMD package
Applications
n Mobile phones
n PDAs
n Portable electronic devices
Typical Application
201073J3
FIGURE 1. Typical Audio Amplifier Application Circuit
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