adi 公司的ad5203是集成了smbus 和pwm輸入的8串白光led(wled)驅動器,采用電流模式和升壓轉換器技術,具有高效率.ad5203集成了0.15 Ω, 2.9 a的開關,工作頻率在350khz和1mhz間選擇.輸入電壓從6v到21v,最大輸出電壓可調至45v,調光頻率在200hz到10khz間可調,具有led開路和短路故障保護.主要用在筆記本電腦,umpc和監視顯示器.本文介紹了ad5203主要特性,方框圖以及采用無延遲調光模式的smbus接口, dpwm調光模式的pwm接口和dc電流調光模式的pwm接口的典型應用電路.

8-string, white led driver with smbus and pwm input for lcd backlight applications

the add5203 is a white led driver for backlight applications based on high efficiency, current-mode, step-up converter technology. it is designed with a 0.15 Ω, 2.9 a internal switch and a pin-adjustable operating frequency between 350 khz and 1 mhz.

the add5203 contains eight regulated current sources for uniform brightness intensity. each current source can be driven up to 30 ma, and the led driving current is pin adjustable by an external resistor. the add5203 drives up to eight parallel strings of multiple series connected leds with a ±1.5% current matching between strings.

the add5203 provides various dimming modes. each dimming mode is selectable with an external dimming mode selection pin. the led dimming control interface can be achieved through pwm input and/or smbus.

the device provides adjustable output dimming frequency range from 200 hz to 10 khz by an external resistor and capacitor. the add5203 operates over an input voltage range of 6 v to 21 v, but the device can function with a voltage as low as 5.6 v.

the add5203 also has multiple safety protection features to prevent damage during fault conditions. if any led is open or short, the device automatically disables the faulty current source. the internal soft start prevents inrush current during startup. thermal shutdown protection prevents thermal damage.

the add5203 is available in a low profile, thermally enhanced, 4 mm × 4 mm × 0.75 mm, 28-lead, rohs-compliant lead frame chip scale package (lfcsp_wq) and is specified over the industrial temperature range of −25℃ to +85℃.

ad5203主要特性:

white led driver based on inductive boost converter

integrated 50 v mosfet with 2.9 a peak current limit

input voltage range: 6 v to 21 v

maximum output adjustable up to 45 v

350 khz to 1 mhz adjustable operating frequency

overvoltage protection (ovp) up to typical 47.5 v

built-in soft start for boost converter

drives up to eight led current strings

led current adjustable up to 30 ma for each channel

headroom control to maximize efficiency

adjustable dimming frequency: 200 hz to 10 khz

led open and short fault protection

selectable dimming control interface methods

pwm input

smbus serial input

selectable dimming modes

fixed delay pwm dimming control with 8-bit resolution

no delay pwm dimming control with 8-bit resolution

direct pwm dimming control

dc current dimming control with 8-bit resolution

general

thermal shutdown

undervoltage lockout

28-lead, 4 mm × 4 mm × 0.75 mm lfcsp_wq

ad5203應用:

notebook pcs, umpcs, and monitor displays


圖1.ad5203電路方框圖

圖2.ad5203典型應用電路:采用無延遲調光模式的smbus接口

圖3.ad5203典型應用電路:采用dpwm調光模式的pwm接口

圖4.ad5203典型應用電路:采用dc電流調光模式的pwm接口