Freescale MC34825 Micro-USB接口方案

Freescale 公司的MC34825 是Micro-USB接口IC,支持通用充电解决方案,支持USB或UART R/D测试电缆,和高速480Mbps USB2.0兼容,支持32个ID电阻值,I2C接口,待机模式的静态电流10uA.本文介绍MC34825主要特性, 简化方框图, 简化应用框图和手机系统的接口电路框图.

Micro-USB Interface IC Supporting Universal Charging Solution and Wired Accessories

The 34825 is designed to support the Universal Charging Solution (UCS) recommended by the OMTP (Open Mobile Terminal Platform), as well as to use the same 5-pin micro or mini-USB connector for other wired accessories. The 34825 supports various types of external power supplies, such as a dedicated ac/dc adapter or a USB port, to charge the battery. It has functions built in to identify the type of the power supply, and sets low or high charging current, based on the current capability of the power supply. The 34825 monitors the power supply, and offers an up to 28 V of over-voltage protection (OVP) to the cell phone against failed power supplies. The 34825 also contains analog switches to multiplex the 5 pins, to support UART and high speed USB data communication, mono or stereo audio headset with or without a microphone and a cord remote controller, manufacturing or research-and-development (R/D) test cables, and other accessories.

The 34825 monitors both the VBUS status and the resistance between the ID pin and the ground to identify the accessory being plugged into the mini or micro-USB connector. A high-accuracy 5-bit ADC is offered to distinguish 32 levels of ID resistance that are assigned to buttons in a cord remote controller or to identification (ID) resistors of accessories. After identifying the attached accessory, the 34825 sends an interrupt signal to a host IC and the host IC can configure the analog switches via an I2C serial bus for further actions. When the accessory is detached from the cell phone, an interrupt signal is also sent to inform the host.

MC34825主要特性:

•Identifies various types of power supplies to set low or high battery-charging-current levels

•Internal power switch to offer OVP against up to 28 V failed power supply input

•Supports stereo/mono headset with or without microphone and remote controller with pure passive components

•Supports USB or UART R/D test cables

•High speed (480 Mbps) USB 2.0 compliant

•Supports 32 ID resistance values with a high accuracy 5-bit ADC

•Accessory attachment and detachment detection with an interrupt signal to the host IC

•I2C interface

•10 μA quiescent current in Standby mode

•Pb-free packaging designated by suffix code EPI2CVDDIOI2C

图1.MC34825简化内部方框图

图2.MC34825简化应用框图

图3.手机系统的接口电路框图