原标题：Maxim MAX97220差分输入耳机放大器解决方案

　　Maxim公司的MAX97220A/B是差分输入的线路/耳机放大器,5V电源时能以3VRMS驱动1K欧姆线路负载, 3.3V电源时能以2VRMS驱动600欧姆线路负载,工作电压2.5V-5.5V, DirectDrive输出,不需要隔直流电容,THD+N优于90dB,18位SNR性能达112dB,主要用于STB,蓝光和DVD播放器,LCD电视和音频设备.本文介绍了MAX97220主要特性, 功能方框图, MAX97220A评估板主要特性,电路图,材料清单和PCB元件布局图.

　　The MAX97220A/B is a differential input DirectDrive® line driver/headphone amplifier. This device is capable of driving line level loads with 3VRMS into 1kI with a 5V supply and 2VRMS into 600I loads from a 3.3V supply. A headphone load is capable of being driven with 125mW into 32I with a 5V supply. The IC is offered with an inter­nally fixed 6dB gain or an externally set gain through external resistors. The external gain setting nodes can also be used to configure filters for set-top box applica­tions. The IC has exceptional THD+N over the full audio bandwidth.

　　Two versions of the IC are available with different turn-on times (tON). The A and C versions for headphone applications feature a tON of 5.5ms while the B and D versions, intended for set-top-box applications, feature a 130ms tON. An on-chip charge pump inverts the power-supply input, creating a negative rail. The output stage of the amplifier is powered between the positive input sup­ply and the output of the charge pump. The bipolar sup­plies bias the output about ground, eliminating the need for large, distortion-introducing output coupling capaci­tors. The IC powers on and off without clicks or pops.

　　The IC is available in a 3mm x 3mm x 0.8mm, 16-pin TQFN and is specified over the extended -40NC to +85NC temperature range.

　　MAX97220主要特性:

　　Output Power 125mW into 32I with a 5V Supply

　　3VRMS Output Drive into 1kI with a 5V Supply

　　2VRMS Output Drive into 600I with a 3.3V Supply

　　Fully Differential Inputs

　　Fixed or Externally Adjustable Gain with No Clicks or Pops

　　Wide 2.5V to 5.5V Operating Range

　　DirectDrive Outputs Eliminate DC-Blocking Capacitors

　　Flat THD+N, Better Than 90dB in the Audio Band

　　18-Bit SNR Performance, 112dB

　　Footprint Compatible with the MAX9722

　　Simple Multimedia Interfaces

　　MAX97220应用:

　　Set-Top Boxes

　　Blu-rayK and DVD Players

　　LCD Televisions

　　Prosumer Audio Devices

　　图1.MAX97220功能方框图

　　图2.MAX97220简化方框图

　　图3.MAX97220A和MAX9722 PCB布局图

　　图4.MAX97220A/B增益设定图

　　MAX97220A评估板

　　The MAX97220A evaluation kit (EV kit) is a fully assembled and tested circuit board that evaluates the MAX97220A differential input DirectDrive® line driver/headphone amplifier. The device is capable of driving 125mW into 32Ω, or 3VRMS into 600Ω load, with a 5V supply.

　　The EV kit provides an externally set gain, is powered from a 2.5V to 5.5V single power supply, and includes a shutdown input. The EV kit also evaluates the MAX97220B, MAX97220C, and MAX97220D devices. Request a free MAX97220B, MAX97220C, and/or MAX97220D IC sample from the factory when ordering the EV kit.

　　MAX97220A评估板主要特性:

　　2.5V to 5.5V Single-Supply Operation

　　3VRMS Output Drive Into 600ω Load

　　125mW Headphone Amplifier

　　Fully Differential Inputs

　　Externally Adjustable Gain

　　Low-Power Shutdown Input

　　Evaluates the MAX97220B, MAX97220C, and MAX97220D (with IC Replacement)

　　Fully Assembled and Tested

　　图5.MAX97220A评估板电路图

　　MAX97220A评估板材料清单(BOM):