基于AS3645的LED闪光驱动设计方案

Austriamicrosystems公司的AS3645是超小型高效单/双路LED闪光驱动器,它的DC/DC升压转换器工作频率高达2MHz,具有软起动功能,闪光停止,过压,超稳,欠压和LED短路保护功能.单路闪光LED电流高达700mA, 双路闪光LED电流高达1000mA,主要用于手机,数码相机和PDA的闪光/火炬.本文介绍AS3645主要特性, 内部方框图,以及典型工作电路图, 采用基带I2C模式, 照相机I2C模式和并行接口模式的应用电路图.

AS3645:1000/720mA Ultra Small High efficient single/dual LED Flash Driver with Safety Features

The AS3645 is an inductive high efficient DCDC step up converter with two current sources. The DCDC step up converter operates at a fixed frequency of 2MHz and includes soft startup to allow easy integration into noise sensitive RF systems. The two current sources (one for driving one or two flash LEDs and one for the indicator LED) can operate in flash / torch / assist (=video) light / indicator modes. If a two flash LEDs configuration is used, the LEDs are connected in series. Therefore identical current is guaranteed.

The AS3645 includes flash timeout, overvoltage, overtemperature, undervoltage and LED short circuit protection functions.

The AS3645 can be controlled either with parallel interface mode to allow simple integration. Alternatively it can be controlled by I2C mode to allow a more sophisticated
control of all settings like currents and timings.

The interface is selected by a dedicated pin (I2C/EN). The AS3645 is available in a space-saving WL-CSP package measuring only 2x1.6mm and operates over the -30℃ to +85℃ temperature range.

AS3645主要特性:

High efficiency 2MHz fixed frequency DCDC Boost converter with soft start allows small coils

- Stable even in coil current limit

High Flash LED(s) current (720mA for single flash LED, 1000mA (2x500mA) for dual flash LED)

Separate Indicator LED output

Flash LED(s) cathode connected to ground:

Improved thermal performance (ground = heat sink)

Simplified PCB layout

Flash, Torch, Assist and Indicator Mode

Protection functions:

Automatic Flash Timeout timer to protect the LED(s)

Overvoltage and undervoltage Protection

Overtemperature Protection

LED(s) short circuit protection

Dual Interface selectable by pin (parallel interface mode and I2C mode)

Available in tiny WL-CSP Packages

3x4 balls 0.5mm pitch, 2x1.6mm package size

AS3645应用:

Flash/Torch for mobile phones, digital cameras and PDA

图1.AS3645内部方框图

图2.AS3645典型工作电路图

图3.AS3645采用基带I2C模式的应用电路图

图4.AS3645采用照相机I2C模式的应用电路图

图5.AS3645采用并行接口模式的应用电路图