| 品牌：ACM | 型号：ACM3220 | 类型：其他IC |
| 封装：QFN4*4-16 |
1. Features ? Wide Power Supply Range: 2.5V to 5.5V ? Gain Settings: -6dB, 0dB, 3dB, and 6dB ? High Power Supply Noise Rejection - 100 dB PSRR at 217 Hz - 90 dB PSRR at 10kHz ? Eliminates Need for DC-Blocking Capacitors - Outputs Biased at 0V - Improves System Noise Performance ? Fully Differential or Single-Ended Inputs - Built-In Resistors Reduces Component Count - Improves System Noise Performance ? Short-Circuit and Thermal-Overload Protection ? 2.3 mA Typical Supply Current ? Constant Maximum Output Power from 2.5V to 5.5V ? Active Click and Pop Suppression ? +8 kV HBM ESD Protected Outputs ? Small Package Available - 16-Pin, 3 mm × 3mm Thin QFN 2. Applications ? Notebook PCs ? Cellular Phones ? PDAs ? Smart Phones ? Portable Audio Equipment ? MP3 Players 3. General Description The ACM3220 is a stereo headphone amplifier that eliminates the need for external dc-blocking output capacitors. Differential stereo inputs and built-in resistors. Differential stereo inputs and built-in resistors set the device gain, further reducing external component count. Gain is selectable at -6dB, 0dB, 3dB or 6dB. The amplifier drives 36mW into 32? speakers from a single 3.6V supply. The ACM3220 provides a constant maximum output power independent of the supply voltage, thus facilitating the design for prevention of acoustic shock. The ACM3220 features fully differential inputs to reduce system noise pickup between the audio source and the headphone amplifier. The high power supply noise rejection performance and differential architecture provides increased RF noise immunity. For single-ended input signals, connect INL+ and INR+ to ground. The device has built-in pop suppression circuitry to completely eliminate disturbing pop noise during turn-on and turn-off. The amplifier outputs have short-circuit and thermal-overload protection along with +8 kV HBM ESD protection, simplifying end equipment compliance to the IEC 61000-4-2 ESD standard. The ACM3220 operates from a single 2.5V to 5.5V supply with 2.3mA of typical supply current. Shutdown mode reduces supply current to less than 1μA.
耳放选型及指标对比
耳放***指标个人认为是底噪，毕竟比较直接影响体验。耳机直接罩在耳朵上的，对信噪比要求比较高，现在音箱的客户都开始用一拳做标准了，何况耳放。所以现在各***都非常关注信噪比。
当工程师设计一款高性能耳机时候就开始考虑耳放，它不仅起到了功率放大的作用，还能够使耳机所表现出来的音乐细节与控制张力更加出色，提高声音的清晰度和层次感。不过，并不是所有的耳机都需要用到耳放，耳放常用来驱动哪些高阻抗/低灵敏度的耳机，以便充分发挥出这些***耳机的真正实力。
耳放***指标个人认为是底噪，毕竟比较直接影响体验。耳机直接罩在耳朵上的，对信噪比要求比较高，现在音箱的客户都开始用一拳做标准了，何况耳放。所以现在各***都非常关注信噪比。
ACM3220 底噪测试
***个关键指标就是功耗了，这方面静态电流是重点。据说电池原材料又要涨价了，老板们盯着电池成本，年轻的消费者才懒得给你频繁充电，影响体验感。
静态电流这个还要关注一个点就是跟电池的关系，电池的电压范围从2.7-4.2V动态变化的，静态电流这个指标，有的是跟电压关系不是很大，有的型号就会跟随电池电压变化。
