Aaustriamicrosystems 公司的AS3561 是用于手提设备的H类立体声耳机放大器，集成了DC/DC降压转换器，工作电压2.5V 到 5.5V，能向16欧姆提供2x30mW输出功率和0.02% THD，1Vrms时的SNR大于100dB，采用I2C控制接口。主要用在手机，PND和手提媒体设备。本文介绍了AS3561主要特性，方框图和I2C方框图以及AS3561应用板电路图和外接元件数值。

AS3561：Class-H Stereo Headphone Amplifier

The AS3561 is a Class-H stereo headphone amplifier optimized for usage within portable devices. The Class-H supply rail adaptation is implemented by an integrated DCDC buck converter that takes its input directly from the battery. The continuous adaption of supply
rails is done according to the input signal swing and load conditions.

This architecture implements significant power savings compared to traditional Class-AB amplifiers.

An I2C control interface is implemented for a 32-step volume control. The integrated charge pump generates a symetric negative supply for true ground output signal levels without the need of output coupling capacitors.

A supervisory circuit is included for overtemperature and shortcircuit protection. Differential inputs together with output ground sensing guarantees very low noise sensitivity.

AS3561主要特性：

Class-H amplifier with integrated DCDC buck converter

- 2x30mW, 0.02% THD @16Ω

- >100dB SNR @1Vrms

Charge pump for true ground output without coupling capacitors

Direct battery connection with wide supply range: 2.5V to 5.5V

Low power consumption optimized for battery operation

- 1 mA quiescent current with both channels enabled

- <5 μA shutdown current

Fully Differential Inputs reduce system noise

- Also configurable as Single-Ended Inputs

SGND pin for ground sensing and ground feedback minimizes sensitivity to interference

I2C control interface

- volume control with 32 gain steps, -59 to +4dB, <-80dB mute

- Channel independent enable control Current and Temperature Supervisor

Package: 0.4 mm Pitch WCSP (1.615x1.615mm)

AS3561应用：

Mobile Phones

Portable Navigation Devices

Media Devices