基于AS3645的LED閃光驅(qū)動(dòng)設(shè)計(jì)方案

Austriamicrosystems公司的AS3645是超小型高效單/雙路LED閃光驅(qū)動(dòng)器,它的DC/DC升壓轉(zhuǎn)換器工作頻率高達(dá)2MHz,具有軟起動(dòng)功能,閃光停止,過(guò)壓,超穩(wěn),欠壓和LED短路保護(hù)功能.單路閃光LED電流高達(dá)700mA, 雙路閃光LED電流高達(dá)1000mA,主要用于手機(jī),數(shù)碼相機(jī)和PDA的閃光/火炬.本文介紹AS3645主要特性, 內(nèi)部方框圖,以及典型工作電路圖, 采用基帶I2C模式, 照相機(jī)I2C模式和并行接口模式的應(yīng)用電路圖.

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應(yīng)用:

Flash/Torch for mobile phones, digital cameras and PDA

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圖1.AS3645內(nèi)部方框圖

圖2.AS3645典型工作電路圖

圖3.AS3645采用基帶I2C模式的應(yīng)用電路圖

圖4.AS3645采用照相機(jī)I2C模式的應(yīng)用電路圖

圖5.AS3645采用并行接口模式的應(yīng)用電路圖