IntersilISL97684四路TFT-LCD显示LED背光驱动方案

Intersil公司的ISL97684是用于中等尺寸TFT-LCD背光的四路LED驱动器,输入电压低到4V,输出电压高达45V.还提供8位PWM调光,在时的线性度低至0.009%,或30kHz时为1.35%,主要应用在平板PC和笔记本电脑显示LED背光,PMP LED背光.本文介绍了ISL97684主要特性, 方框图,以及单电源,双电源应用电路和PWM调光应用电路.

The ISL97682, ISL97683, ISL97684 are Intersil’s highly integrated 2-3-4-channels LED drivers that are suitable for medium size TFT-LCD backlights. These parts can drive multiple channels of LEDs from inputs as low as 4V to outputs of up to 45V. They can also operate from inputs as low as 3V to outputs of up to 26.5V in bootstrap configuration.

The ISL97682, ISL97683, ISL97684 feature optional channels phase shift control. This feature is used to minimize the input, output ripple characteristics and load transient, which help eliminate or reduce the video and audio noise interference from the backlight driver operation.

The ISL97682, ISL97683, ISL97684 offer 8-bit PWM dimming for systems that need frequency tuning flexibility. With the unique adaptive boost switching architecture, the ISL97682, ISL97683, ISL97684 also offer Direct PWM dimming with output, which follows input and achieves linearity as low as 0.009% at 200Hz or 1.35% at 30kHz.

The drivers incorporate dynamic headroom control that monitors the highest LED forward voltage string and uses its feedback signal for the minimum output regulation. The ISL97682, ISL97683, ISL97684 incorporates extensive fault protection functions including
string open and short circuit detections, OVP, and OTP. The switching frequency can be selected at either 600kHz or 1.0MHz in PFM or PWM mode. These parts are available in the thin and compact 16 Ld 3mmx3mm TQFN package and operate in ambient temperature from -40℃ to +85℃.

ISL97684主要特性:

· ISL97682 - 2 x 100mA Channels

· ISL97683 - 3 x 50mA Channels

· ISL97684 - 4 x 50mA Channels

· Input Voltage 4.0V~26.5V with Max VOUT of 45V

· Input Voltage 3.0V (see Figure 26)~24V with Max VOUT of 26.5V

· PWM Dimming Linearity

- PWM Dimming with Adjustable Dimming Frequency with Duty Cycle Linear from 0.4% to 100% <30kHz

- Direct PWM Dimming with Duty Cycle Linear from 0.009% to 100% at 200Hz

· Current Matching of 0.7% typical from 1%~100% Dimming

· Selectable 600kHz or 1MHz Switching Frequency in PWM/PFM Mode

· Dynamic Headroom Control

· Fault Protection

- String Open/Short Circuit Protections, OVP, OTP

· Thin and Compact TQFN-16 3mmx3mm Package

ISL97684应用:

· Tablet to Notebook PC Displays LED Backlighting

· PMP LED Backlighting

图1.ISL97684方框图

图2.ISL97684单电源3V应用电路图

图3.ISL97684双电源2.7V应用电路图

图4.ISL97684直接PWM调光应用电路图

图4.ISL97684 采用RFPWM频率可调的PWM调光应用电路图

详情请见:
http://www.intersil.com/data/fn/fn7689.pdf