原标题：安森美 NCP2991 1.35W音频功率放大方案

　　安森美(On Semi)公司的 NCP2991是1.35W具有可选择快速开通时间的音频功率放大器,电源5.0V时可向8欧姆BTL负载提供连续输出功率1.35W,3.6V电源时可向4.0欧姆BTL负载提供1.1W. NCP2991的工作电压从2.5V到5.5V,PSRR可高达-100dB,关断模式的超低功耗为10nA,主要用在手提电子设备,PDA和无线手机.本文介绍了NCP2991的主要特性, 单端输入和差分输入的音频放大器应用电路以及演示板电路图与材料清单(BOM).

　　NCP2991 1.35 Watt Audio Power Amplifier with Selectable Fast Turn On Time

　　The NCP2991 is an audio power amplifier designed for portable communication device applications such as mobile phone applications. The NCP2991 is capable of delivering 1.35 W of continuous average power to an 8.0__ BTL load from a 5.0 V power supply, and 1.1 W to a 4.0 _ BTL load from a 3.6 V power supply.

　　The NCP2991 provides high quality audio while requiring few external components and minimal power consumption. It features a low−power consumption shutdown mode, which is achieved by driving the SHUTDOWN pin with logic low.

　　The NCP2991 contains circuitry to prevent from “pop and click” noise that would otherwise occur during turn−on and turn−off transitions. It is a zero pop noise device when a single ended or a differential audio input is used.

　　For maximum flexibility, the NCP2991 provides an externally controlled gain (with resistors). In addition, it integrates 2 different Turn On times (15 ms or 30 ms) adjustable with the TON pin. Due to its superior PSRR, it can be directly connected to the

　　battery, saving the use of an LDO. This device is available in a 9−Pin Flip−Chip CSP (Lead−Free).

　　NCP2991主要特性:

　　1.35 W to an 8.0 _ BTL Load from a 5.0 V Power Supply

　　Best−in−Class PSRR: up to −100 dB, Direct Connection to the Battery

　　Zero Pop Noise Signature with a Single Ended Audio Input

　　Ultra Low Current Shutdown Mode: 10 nA

　　2.5 V−5.5 V Operation

　　External Gain Configuration Capability

　　External Turn−on Time Configuration Capability: 15 ms or 30 ms

　　Thermal Overload Protection Circuitry

　　This is a Pb−Free Device*

　　NCP2991典型应用:

　　Portable Electronic Devices

　　PDAs

　　Wireless Phones

　　图1.单端输入音频放大器应用电路

　　图2.差分输入音频放大器应用电路

　　图3.NCP2991演示板电路图

　　NCP2991演示板材料清单(BOM):