LM4670

LM4670 Filterless High Efficiency 3W Switching Audio Amplifier December 2004 LM4670 Filterless High Efficiency 3W Switching Audio Amplifier General Description The LM4670 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 external component count, simplifies circuit design, and reduces board area. The LM4670 processes analog inputs with a deltasigma modulation technique that lowers output noise and THD when compared to conventional pulse width modulators. The LM4670 is designed to meet the demands of mobile phones and other portable communication devices. Operating on a single 5V supply, it is capable of driving a 4Ω speaker load at a continuous average output of 2.3W with less than 1% THD+N. Its flexible power supply requirements allow operation from 2.4V to 5.5V. The LM4670 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 77%, reaching 88% at 600mW output power. The LM4670 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 LM4670 is externally configurable which allows independent gain control from multiple sources by summing the signals. Key Specifications j Efficiency at 3.6V, 100mW into 8...