原标题：TI PCM186x系列音频前端子系统解决方案

　　TI公司的PCM186x系列是音频前端器件,不需要5V电源或外接可编增益放大器,和欧洲Ecodesign法规兼容,集成了可替代某些DSP功能的许多系统级的功能,从而能以降低成本方式实现更小更智能的产品,采用3.3V电源,主要用在汽车,家庭影院,网络照相机和音响中的音频子系统.本文介绍了PCM186x系列主要特性,内部框图以及评估板PCM1865EVM主要特性,框图,电路图,材料清单和PCB元件布局图.

　　The PCM186x family of audio front-end devices takes a new approach to audio-function integration to ease compliance with European Ecodesign legislation while enabling high-performance end products. With no need for a 5-volt supply or an external programmable-gain amplifier, smaller, smarter products are feasible at reduced cost.

　　The PCM186x’s highly flexible audio front end supports input levels from small-mV microphone inputs to 2.1VRMS line Inputs without external resistor dividers. The PCM186x family integrates many system-level functions that assist or replace some DSP functions.

　　All these features are available using a single 3.3V power supply. An integrated bandgap voltage reference provides excellent PSRR, so that a dedicated analog 3.3V rail may not be required.

　　PCM186x系列主要特性:

　　Universal Analog Mic Input, 2.1VRMS Full Scale

　　8 Analog Inputs with MUX and PGA

　　Analog pre-mix function before PGA/MUX

　　Single Ended, Pseudo-Differential or Differential Inputs with Mic Bias

　　4x Digital Microphone Inputs

　　Up to 4 Mono ADC channels (PCM1865)

　　Hardware Control (PCM1861)

　　I2C or SPI Control (PCM1863/5)

　　H/W Programmable Gain Amplifier

　　Fixed Mic Pregainselect : 20, 32dB (Analog)

　　S/W Programmable Gain Amplifier

　　Integrated High Performance Audio PLL

　　Single 3.3V Supply for Analog and Digital

　　Additional 1.8V Core and Interface for lower

　　power consumption

　　Power Dissipation at 3.3V: <85mW (PCM1861/3),

　　<145mW (PCM1865)

　　‘Energysense’ Audio Content Detector - for auto

　　system wakeup and sleep

　　Master or Slave Audio Interface:

　　Mixer functionality:

　　Digital Mixer to mix ADC outputs and I2S

　　synchronous inputs

　　Zero Crossing PGA Gain changes

　　Automatic PGA Clipping Suppression control

　　PCB-footprint compatibility across all 3 devices

　　PCM186x系列主要应用:

　　Audio Subsystem: Automotive Head Unit & Trunk Amp

　　Audio Subsystem: Home Theater in a Box (HTiB)

　　Audio Subsystem: PC Speaker

　　Audio Subsystem: Speaker Dock

　　Audio Subsystem: Automotive Head Unit

　　Audio Subsystem: Network Cameras

　　Audio Subsystem: Sound Bar (Low End)

　　Network Cameras Subsystem

　　图1.PCM186x系列内部框图

　　PCM186x系列评估板PCM1865EVM

　　PCM1865EVM 110 dB 4ch S/W Controlled Audio ADC With Universal Front End Evaluation Module

　　The PCM1865EVM (EVM) is an easy-to-use board for full evaluation of the four channel PCM1865 ADC. The included USB-12X board connects the EVM to the PC and provides 5V power. The EVM is controlled by PurePathTM Console which gives the ability to load, run and save scripts.

　　The PCM186xEVM has an external +5-V power connection or USB +5 V through the USB-I2X board topower the EVM. In conjunction with the USB-I2X board, all of the register programming can be done viaUSB. In the case of the hardware-controlled parts, resistors are included to tie inputs high or low. Thereare headers and test points for most signals to and from the PCM186x. Digital audio can be streamedfrom the included SPDIF optical connectors or though a USB to a PC.

　　评估板PCM1865EVM主要特性:

　　Simple external 5V power connection or USB power from USB-I2X

　　All of the register programming can be done via USB through USB-I2X using PurePathTM Console

　　Headers and test points available for most signals to and from the PCM1865

　　Digital Audio can be streamed from the included SPDIF optical connectors or through a USB to a PC

　　An on board PCM9211 allows the EVM to receive and transmit digital audio via optical/SPDIF connectors

　　图2.评估板PCM1865EVM外形图

　　图3.USB-I2X板外形图

　　图4.评估板PCM1865EVM和USB-I2X板连接图

　　图5.评估板PCM1865EVM框图

　　评估板PCM1865EVM材料清单(BOM):