原标题：Wolfson WM8994智能手机多路音频CODEC方案

　　Wolfson公司的WM8994是高度集成智能手机用超低功耗高保真音频CODEC,具有高保真24位4路DAC和2路ADC,立体声DAC播放的SNR为100dB(A加权),1W立体声/2W单声道D类/AB类扬声器驱动器,无电容W类耳机驱动器,智能的MIC接口和高性能模拟MIC接口,主要应用在智能手机和音乐手机,手提导航仪和移动互联网设备(MID).本文介绍了WM8994主要特性,方框图, 采用数字MIC和数字音频接口的智能手机方框图以及WM8994评估板,功能方框图,详细电路图和所用材料清单(BOM).

　　The WM8994 is a highly integrated ultra-low power hi-fi CODEC designed for smartphones and other portable devices rich in multimedia features.

　　An integrated stereo class D/AB speaker driver and class W headphone driver minimize power consumption during audio playback.

　　The device requires only Vbatt and a 1.8V supply, generating all other internal supply rails from integrated LDOs.

　　Stereo full duplex asynchronous sample rate conversion and multi-channel digital mixing combined with powerful analogue mixing allow the device to support a huge range of different architectures and use cases.

　　A fully programmable parametric EQ provides speaker compensation and a dynamic range controller can be used in the ADC or DAC paths for maintaining a constant signal level, maximizing loudness and protecting speakers against overloading and clipping.

　　A smart digital microphone interface provides power regulation, a low jitter clock output and decimation filters for up to four digital microphones. A MIC activity detect with interrupt is available.

　　Active ground loop noise rejection and DC offset correction help prevent pop noise and suppress ground noise on the headphone outputs.

　　WM8994主要特性:

　　• Hi-Fi 24-bit 4-channel DAC and 2-channel ADC

　　• 100dB SNR during stereo DAC playback (‘A’ weighted)

　　• Smart MIC interface

　　- Power, clocking and data input for up to four digital MICs

　　- High performance analogue MIC interface

　　- MIC activity monitor & interrupt allows processor to sleep

　　• 1W stereo / 2W mono class D/AB speaker driver

　　• Capless class W headphone drivers

　　- Integrated charge pump

　　- 6mW total power for DAC playback to headphones

　　• 4 line outputs (single-ended or differential)

　　• BTL earpiece driver

　　• Digital audio interfaces for multi-processor architecture

　　- Asynchronous stereo duplex sample rate conversion

　　- Powerful mixing and digital loopback functions

　　• ReTuneTM Mobile 5-band, 6-channel parametric EQ

　　• Programmable dynamic range controller

　　• Dual FLL provides all necessary clocks

　　- Self-clocking modes allows processor to sleep

　　- All standard sample rates from 8kHz to 96kHz

　　• Active noise reduction circuits

　　- DC offset correction removes pops and clicks

　　- Ground loop noise cancellation

　　• Integrated LDO regulators

　　• 72-ball W-CSP package (4.511mm x 4.023mm x 0.7mm)

　　WM8994应用:

　　• Smartphones and music phones

　　• Portable navigation

　　• Mobile internet devices

　　图1.WM8994方框图

　　图2.采用数字MIC和数字音频接口的WM8994智能手机方框图

　　WM8994评估板

　　The WM8994 is a highly integrated ultra-low power hi-fi CODEC designed for smartphones and other portable devices rich in multimedia features. This evaluation platform has been designed to allow the user ease of use and give optimum performance in device measurement as well as providing the user with the ability to listen to the excellent audio quality offered by the WM8994.

　　图3.WM8994评估板功能方框图

　　图4.WM8994评估板电路图:S/PDIF接口

　　图5.WM8994评估板电路图:USB接口

　　图6.WM8994评估板电路图:控制I/F电平转移

　　图7.WM8994评估板电路图:音频I/F电平转移

　　图8.WM8994评估板电路图:音频输入

　　图9.WM8994评估板电路图:DUT插座

　　图10.WM8994评估板电路图:音频输出

　　图11.WM8994评估板电路图:GPIO接口

　　图12.WM8994评估板电路图:USB电源1

　　图13.WM8994评估板电路图:USB电源2

　　图14.WM8994评估板电路图:外接电源

　　图15.WM8994评估板电路图:Mini板ID

　　WM8994评估板材清单(BOM):