Aaustriamicrosystems 公司的AS3561 是用于手提設備的H類立體聲耳機放大器，集成了DC/DC降壓轉換器，工作電壓2.5V 到 5.5V，能向16歐姆提供2x30mW輸出功率和0.02% THD，1Vrms時的SNR大于100dB，采用I2C控制接口。主要用在手機，PND和手提媒體設備。本文介紹了AS3561主要特性，方框圖和I2C方框圖以及AS3561應用板電路圖和外接元件數值。
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應用：
Mobile Phones
Portable Navigation Devices
Media Devices
圖1。AS3561方框圖
圖2。AS3561 I2C方框圖
圖3。AS3561應用板電路圖
外接元件數值：
1 x 3.3 uH Coil (SW-HPVDD)
7 x 2.2 uH ±10% X5R (AVDD, CPP-CPN, HPVSS, INRP, INRN, INLP, INLN)
1 x 10 uH ±10% X5R (HPVDD)
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