MAX98357A PCM输入D类音频放大器解决方案

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Maxim公司的MAX98357A/MAX98357B是数字脉码调制(PCM)输入D类放大器,提供AB类音频性能和D类效率,有五个可选择的增益设定(3dB, 6dB, 9dB, 12dB和15dB),单电源2.5V-5.5V工作,5V 4Ω时的输出功率为3.2W,效率92% (RL = 8Ω, POUT = 1W),输出噪音25μVRMS (AV = 15dB),1kHz时的THD+N为0.015%,主要用在笔记本电脑和上网本(Netbook),手机和平板电脑.本文介绍了MAX98357A/MAX98357B主要特性,功能框图和几种应用电路,以及MAX98357开发板DEV(WLP)主要特性,框图,电路图,材料清单和PCB设计图.

The MAX98357A/MAX98357B are digital pulse-code mod-ulation (PCM) input Class D power amplifiers that provide Class AB audio performance with Class D efficiency. These ICs offer five selectable gain settings (3dB, 6dB, 9dB, 12dB, and 15dB) in I2S/left-justified mode set by a single gain select input and a fixed 12dB gain in TDM mode.

The digital audio interface is highly flexible with the MAX98357A supporting I2S data and the MAX98357B supporting left-justified data. Both ICs support 8 channel time division multiplexed (TDM) data. The digital audio interface accepts specified sample rates between 8kHz and 96kHz for all supported data formats. The ICs can be configured to produce a left channel, right channel, or (left/2 + right/2) output from the stereo input data. The ICs operate using 16/24/32-bit data for I2S and left-justified modes as well as 16-bit or 32-bit data using TDM mode. The ICs eliminate the need for the external MCLK signal that is typically used for PCM communication. This reduc-es EMI and possible board coupling issues in addition to reducing the size and pin count of the ICs.

The ICs also feature a very high wideband jitter toler-ance (12ns typ) on BCLK and LRCLK to provide robust operation.Active emissions-limiting, edge-rate limiting, and over-shoot control circuitry greatly reduce EMI. A filterless spread-spectrum modulation scheme eliminates the need for output filtering found in traditional Class D devices and reduces the component count of the solution.

The ICs are available in 9-pin WLP (1.345mm x 1.435mm x 0.64mm) and 16-pin TQFN (3mm x 3mm x 0.75mm) packages and are specified over the -40 ℃ to +85℃ tem-perature range.

MAX98357A/MAX98357B主要特性:

Single-Supply Operation (2.5V to 5.5V)
3.2W Output Power into 4Ω at 5V
2.4mA Quiescent Current
92% Efficiency (RL = 8Ω, POUT = 1W)
25μVRMS Output Noise (AV = 15dB)
Low 0.015% THD+N at 1kHz
No MCLK Required
Sample Rates of 8kHz to 96kHz
Supports Left, Right, or (Left/2 + Right/2) Output
Sophisticated Edge Rate Control Enables Filterless Class D Outputs
77dB PSRR at 1kHz
Low RF Susceptibility Rejects TDMA Noise from GSM Radios
Extensive Click-and-Pop Reduction Circuitry
Robust Short-Circuit and Thermal Protection
Available in Space-Saving Packages: 1.345mm x 1.435mm WLP (0.4mm Pitch) and 3mm x 3mm TQFN

MAX98357A/MAX98357B应用:

Notebook and Netbook Computers
Cellular Phones
Tablets

图1.MAX98357A/MAX98357B功能框图

图2.MAX98357A/MAX98357B增益6dB左路PCM工作电路

图3.MAX98357A/MAX98357B增益12dB左路PCM工作电路

图4.MAX98357A/MAX98357B增益6dB右路PCM工作电路

图5.MAX98357A/MAX98357B增益6dB(左路/2+右路/2)PCM工作电路

图6.MAX98357A/MAX98357B采用两个IC的立体声PCM工作电路

图7.MAX98357A/MAX98357B增益12dB通路TDM工作电路

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MAX98357开发板DEV(WLP)

The MAX98357 development board (DEV board) is a fullyassembled and tested PCB that evaluates the MAX98357I2S digital input Class D power amplifier. The DEV boardoperates from a single 2.5V to 5.5V DC power supply andis capable of delivering 3.2W into a 4Ω load. The deviceoutputs can be connected directly to a speaker load forfilterless applications. However, a filter can be added toease evaluation. The MAX98357A accepts standard I2Sdata and the MAX98357B accepts left-justified digital audio data. Both versions also support 8-channel TDMaudio data.

The MAX98357 evaluation system (EV system) includesthe MAX98357 DEV board and Maxim Integrated’s audiointerface board (AUDINT001 board).

The AUDINT001 board provides an easy-to-use USBaudio-to-I2S converter. This allows for any computer tobecome a digital audio source, which can be used toevaluate the devices. The AUDINT001 board can also beused to power the MAX98357. This allows for a completeevaluation from a single USB connection.

MAX98357开发板DEV(WLP)主要特性:

●● 2.5V to 5.5V Single-Supply Operation
●● Only a Single External Component (VDD Capacitor)Required in Many Applications
●● I2S, Left-Justified, or TDM Input
●● Five Selectable Gains (3db, 6dB, 9dB, 12dB, and15dB)
●● Audio Channel Select (Left, Right, and Mono Mix)
●● Filterless Operation
●● Optional Class D Output Filters for Ease ofEvaluation
●● Proven PCB Layout
●● Fully Assembled and Tested

图8.MAX98357开发板DEV(WLP)简化框图

图9.MAX98357开发板DEV(WLP)电路图
MAX98357开发板DEV(WLP)材料清单:



图10.MAX98357开发板DEV(WLP) PCB设计图(1)

图11.MAX98357开发板DEV(WLP) PCB设计图(2)

图12.MAX98357开发板DEV(WLP) PCB设计图(3)

图13.MAX98357开发板DEV(WLP) PCB设计图(4)

图14.MAX98357开发板DEV(WLP) PCB设计图(5)

fidelio

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