MAXIM公司的MAX97003是一款立體聲單聲道揚聲器耳機放大器，揚聲器耳機放大器有獨立的音量及開關控制單元，四路輸入可以配置為兩路差分輸入或四路單端輸入方式。該芯片通過內部集成可調動態(tài)范圍壓縮及失真限制器使揚聲器輸出最大音量，在不衰減大信號品質的情況下提高小信號的增益。本文通過介紹MAX97003芯片的特性、應用方向和內部結構圖實現(xiàn)對該芯片的理解，并通過MAX97003EVKIT開發(fā)參考設計實現(xiàn)快速應用，給出相應開發(fā)板設計特性，原理圖、PCB制板圖及元器件列表。
The MAX97003 audio subsystem combines a mono speaker amplifier with a stereo headphone amplifier. The headphone and speaker amplifiers have independent volume and on/off controls. The four inputs are configurable as two differential or four single-ended inputs.
To minimize output noise, both the headphone and speaker outputs utilize a downward expander/noise gate to attenuate noise when no desired input signal is present.
The speaker output incorporates an adjustable dynamic range compressor (DRC) and distortion limiter to protect the speaker and maximize loudness. This allows high gain for low-level signals without compromising the quality of large signals.
All controls are performed using the two-wire I2C interface. The IC operates in the extended -40°C to +85℃ temperature range, and is available in the 2.0mm x 2.4mm, 20-bump WLP package (0.4mm pitch).
MAX97003主要特性：
2.7V to 5.5V Speaker Supply Voltage
1.8V Headphone Supply Voltage
1.0W Speaker Output (VPVDD = 4.2V, ZSPK = 8Ω + 68μH, 1% THD+N)
32mW/Channel Headphone Output (RHP = 32Ω)
Active Emissions Limiting for Enhanced EMI Reduction
Efficient Class H Headphone Amplifier
Ground-Referenced Headphone Outputs
Headphone Ground Sense
2 Stereo Single-Ended/Mono Differential Inputs
Integrated Expander/Noise Gate for Low Output Noise
Integrated DRC (Speaker Outputs)
Integrated Distortion Limiter (Speaker Outputs)
Extensive Click-and-Pop Reduction Circuitry
TDMA Noise Free
2.0mm x 2.4mm, 20-Bump WLP Package (0.4mm Pitch)
MAX97003應用：
Cell Phones
Portable Media Players
圖1. MAX97003方框圖
MAX97003EVKIT設計方案主要特性：
﹡ 2.7V to 5.5V Single-Supply Operation
﹡Proven Audio PCB Layout
﹡On-Board USB Interface Circuit Generates I2C-Compatible Signals
﹡PCB Pads for User-Supplied I2C-Compatible Signals
﹡Surface-Mount Components
﹡Windows XP-, Windows Vista-, and Windows 7-Compatible Software
﹡Fully Assembled and Tested
MAX97003EVKIT電路圖：
圖3. MAX97003EVKIT(2/2)電路圖
