LM4664 Datasheet, PDF (1/14 Pages) National Semiconductor (TI) – Filterless High Efficiency 1.1W Switching Audio Amplifier

March 2004
LM4664
Filterless High Efficiency 1.1W Switching Audio
Amplifier
General Description
The LM4664 is a fully integrated single-supply high efficiency
switching audio amplifier. It features an innovative modulator
that eliminates the LC output filter used with typical switching
amplifiers. Eliminating the output filter reduces parts count,
simplifies circuit design, and reduces board area. The
LM4664 processes analog inputs with a delta-sigma modu-
lation technique that lowers output noise and THD when
compared to conventional pulse width modulators.
The LM4664 is designed to meet the demands of mobile
phones and other portable communication devices. Operat-
ing on a single 3V supply, it is capable of driving 8Ω trans-
ducer loads at a continuous average output of 425mW with
less than 1%THD+N. Its flexible power supply requirements
allow operation from 2.7V to 5.5V.
The LM4664 has high efficiency with an 8Ω transducer load
compared to a typical Class AB amplifier. With a 3V supply,
the IC’s efficiency for a 100mW power level is 74%, reaching
84% at 425mW output power.
The LM4664 features a low-power consumption shutdown
mode. Shutdown may be enabled by driving the Shutdown
pin to a logic low (GND).
The LM4664 has fixed selectable gain of either 6dB or 12dB.
The LM4664 has short circuit protection against a short from
the outputs to V_DD, GND, or across the outputs.
Key Specifications
j Efficiency at 3V, 100mW into 8Ω transducer 74% (typ)
j Efficiency at 3V, 425mW into 8Ω transducer 84% (typ)
j Efficiency at 5V, 1W into 8Ω transducer 86% (typ)
j Total quiescent power supply current
3.5mA (typ)
j Total shutdown power supply current
0.4µA (typ)
j Single supply range
2.7V to 5.5V
Features
n No output filter required for inductive transducers
n Selectable gain of 6dB or 12dB
n Very fast turn on time: 7ms (typ)
n Minimum external components
n "Click and pop" suppression circuitry
n Micro-power shutdown mode
n Short circuit protection
n Available in space-saving micro SMD package
Applications
n Mobile phones
n PDAs
n Portable electronic devices
Typical Application
200960G5
FIGURE 1. Typical Audio Amplifier Application Circuit
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