来源：Wolfson公司   作者：

Wolfson公司的WM8350立体声CODEC具有功率管理功能,为手提音频和多媒体系统提供了高性价比的单片解决方案. WM8350提供了高质量立体声录音和播放所需的所有功能.片内的可编程放大器能直接连接耳机和麦克风,在ADC输入通路中还集成了可编程的高通滤波器.WM8350包括有6个可编程的DC/DC转换器,4个低压降(LDO)稳压器和一个限流开关,以便为系统每部分产生合适的电压,广泛应用在手提导航设备, VoIP手机,手提音频和多媒体播放器以及其它以单节锂电池为能源的手提系统.本文介绍了WM8350的主要特性,方框图以及系统应用框图.

Wolfson Stereo CODEC with Integrated Power Management The WM8350 is an integrated audio and power management subsystem which provides a cost effective, single-chip solution for portable audio and multimedia systems.

The integrated audio CODEC provides all the necessary functions for high-quality stereo recording and playback. Programmable on-chip amplifiers allow for the direct connection of headphones and microphones with a minimum of external components. A programmable low-noise bias voltage is available to feed one or more electret microphones. Additional audio features include programmable high-pass filter in the ADC input path.

The WM8350 includes six programmable DC-DC converters, four low-dropout (LDO) regulators and a current limit switch to generate suitable supply voltages for each part of the system, including the integrated audio CODEC as well as off-chip components such as a digital core and IO supplies, and LED lighting. An additional on-chip regulator maintains the backup power for always-on functions. The WM8350 can be powered by a lithium battery, by a wall adaptor or USB.
An on-chip battery charger supports both trickle charging and fast (constant current, constant voltage) charging of single-cell lithium batteries. The charge current, termination voltage, and charger time-out are programmable to suit different types of batteries.

Internal power management circuitry controls the start-up and shutdown sequencing of clocks and supply voltages. It also detects and handles conditions such as under-voltage, extreme temperatures, and deeply discharged or defective batteries, with a minimum of software involvement.

Two programmable constant-current sinks are available for driving LED strings, e.g. for display backlights or photo-flash applications, in a highly power-efficient way. Additional RGB LEDs can be driven through GPIO pins.

The WM8350 includes a 32.768kHz crystal oscillator, an internal RC oscillator, a real time clock (RTC) and an alarm function capable of waking up the system. Internal circuitry can independently generate all clock signals required to start up.

The master clock can be input directly or generated internally by an integrated low power FLL. This master clock can be used to drive low-jitter audio clocks from reference clocks of 5 to 20MHz.To extend battery life, fine-grained power management enables each function in the WM8350 to be independently powered down through the control interface.

主要特性:

Stereo Hi-Fi CODEC
DAC SNR 98dB (‘A’ weighted @ 48kHz), THD -84dB
ADC SNR 95dB (‘A’ weighted @ 48kHz), THD -80dB
40mW on-chip headphone driver with ‘capless’ option
16Ω headphone load: THD –70dB, Po = 20mW
2 differential microphone inputs with low-noise bias voltage and programmable preamps

Programmable high-pass filter for ADC
Microphone and Headphone detection
Auxiliary inputs for analogue signals
Sample rates: 8, 11.025, 16, 22.05, 24, 32, 44.1 or 48kHz
System Control
Support for I2C or SPI Control Interface
Handles power sequencing, reset signals and fault conditions
Autonomous power source selection (battery, wall adaptor or USB bus)
Total current drawn from USB bus is limited to comply with USB 2.0 standard and USB OTG supplement
Supply Generation
2 x DC-DC Buck Converters (0.85V - 3.4V, Up to 1A)
2 x DC-DC Buck Converters (0.85V - 3.4V, Up to 500mA)
2 x DC-DC Boost Converters (5V - 20V, 40 to 200mA)
4 x LDO voltage regulators (0.9V - 3.4V, 150mA)
LED Drivers  
2 programmable constant-current sinks, suitable for screen backlight or white LED photo flash
3 open-drain outputs for RGB LEDs
Battery Charger
Single-cell Li-on / Li-Pol battery charger
Thermal protection for charge control; temperature monitoring available for thermal regulation
LED outputs to indicate charge status and fault conditions
Additional Features
“Always on” RTC with wake-up alarm
Watchdog timer
Up to 13 configurable GPIO pins
On-chip crystal oscillator and internal RC oscillator
Low power FLL supporting 32kHz to 19.2MHz input clocks
7x7mm, 129 BGA package, 0.5mm ball pitch

目标应用:
Portable navigation devices
VoIP handsets
Portable audio and media players
Other portable systems powered by single-cell lithium batteries



图1. WM8350方框图



图2. WM8350系统应用方框图