The NCP2991 class AB audio amplifier from ON Semiconductor addresses two crucial requirements in today’s portable and wireless audio applications: noise-free audio amplification and fast response time. According to ON Semiconductor, the amp provides excellent audio performance without sacrificing power efficiency for portable and wireless applications (see the figure).
A power supply rejection ratio (PSRR) of -103 dB eliminates any noise that may be generated by the fluctuation of battery supply voltage. The device is highly resistive to the so-called time-division-multiple-access noise (TDMA) that occurs during Global System Mobile (GSM) transmission. Additionally, the device guarantees zero pop-and-click noise at start-up and shut-down. It has a low typical total harmonic distortion (THD) level (0.015%).
The NCP2991’s start-up time is selectable between 15 and 20 ms. Because of the fast start-up time, the NCP2991 can be kept in shut-down mode when it is not in use. Consequently, much of the time the NCP2991 consumes only 20 nA. The NCP2991 is capable of delivering 1.35 W of output power to an 8-&937; speaker, or 1.1 W to a 4-&937; speaker. It also has built-in thermal overload protection circuitry to disable the device’s operation in case of an over-temperature situation.
The NCP2991 comes in the industrial standard 1.45- by 1.45- by 0.6-mm µBump package and is priced at $0.22 in 3000-unit quantities.