LM4671_08 Datasheet, PDF (1/18 Pages) National Semiconductor (TI) – Filterless High Efficiency 2.5W Switching Audio Amplifier

March 3, 2008
LM4671 
Filterless High Efficiency 2.5W Switching Audio Amplifier
General Description
The LM4671 is a single supply, high efficiency 2.5W switching
audio amplifier. A low noise, filterless PWM architecture elim-
inates 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 op-
eration from 2.4V to 5.5V.
The LM4671 has high efficiency with speaker loads compared
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 al-
lows independent gain control from multiple sources by sum-
ming the signals.
Key Specifications
■ Efficiency @ 3.6V, 100mW into
  8Ω speaker
■ Efficiency @ 3.6V, 400mW into
   8Ω speaker
■ Efficiency @ 5V, 1W into 8Ω
speaker
■ Quiescent current, 3.6V supply
■ Total shutdown power supply
current
■ Single supply range
80% (typ)
88% (typ)
86% (typ)
2.8mA (typ)
0.01µA (typ)
2.4V to 5.5V
Features
■ ^{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 microSMD package}
Applications
■ ^{Mobile phones}
■ ^PDAs
■ ^{Portable electronic devices}
Typical Application
201073j3
FIGURE 1. Typical Audio Amplifier Application Circuit
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