ADI ADP8860背景光LED电荷泵驱动方案

ADI 公司的ADP8860是集成了自动光电晶体管控制的可编程背景光LED电荷泵驱动器,能在黑暗和办公室环境光照条件下改变电流强度,从而大大地节省了电源.光强度阈值能通过I2C接口编程,有7路单独和可编程的LED驱动器(6路驱动器电流30mA,1路驱动器为60mA),可编程最大限流有128等级,待机模式电流小于1uA,主要用于移动显示器背景光和手机键盘背景光,双RGB背景光,LED指示器和小型显示器背景光.本文介绍了ADP8860的主要特性,详细的方框图以及典型应用电路,通用应用电路和带键盘光控制的ADP8860应用电路.

The ADP8860 combines a programmable backlight LED charge pump driver with automatic phototransistor control. This combi-nation allows for significant power savings because it changes the current intensity in office and dark ambient light conditions. By performing this function automatically, it eliminates the need for a processor to monitor the phototransistor.

The light intensity thresholds are fully programmable via the I2C interface. A second phototransistor input, with dedicated comparators, improves the ambient light detection levels for various user operating conditions.

The ADP8860 allows as many as six LEDs to be independently driven up to 30 mA (typical). A seventh LED can be driven to 60 mA (typical). All LEDs are programmable for minimum/max-imum current and fade in/out times via the I2C interface. These LEDs can also be combined into groups to reduce the processor instructions during fade in/out.

Driving this entire configuration is a two-capacitor charge pump with gains of 1×, 1.5×, and 2×. This setup is capable of driving a maximum IOUT of 240 mA from a supply of 2.5 V to 5.5 V. The device includes a variety of safety features including short-circuit, overvoltage, and overtemperature protection. These features allow easy implementation of a safe and robust design. Addi-tionally, input inrush currents are limited via an integrated soft start combined with controlled input-to-output isolation.

The ADP8860 is available in two package types, either a compact 2 mm × 2.4 mm × 0.6 mm WLCSP (wafer level chip scale package) or a small LFCSP (lead frame chip scale package).

ADP8860主要特性:

Charge pump with automatic gain selection of 1×, 1.5×, and 2× for maximum efficiency

Up to two built-in comparator inputs with programmable modes for ambient light sensing

Outdoor, office, and dark modes for maximum backlight power savings

7 independent and programmable LED drivers

6 drivers capable of 30 mA (typical)

1 driver capable of 60 mA (typical)

Programmable maximum current limit (128 levels)

Standby mode for <1 μA current consumption

16 programmable fade in and fade out times

0.1 sec to 5.5 sec

Choose from linear, square, or cubic rates

Fading override

I2C-compatible interface for all programming

Dedicated reset pin and built-in power-on reset (POR)

Short-circuit, overvoltage, and overtemperature protection

Internal soft start to limit inrush currents

Input-to-output isolation during faults or shutdown

Operation down to VIN = 2.5 V with undervoltage lockout (UVLO) at VIN = 2.0 V

Small wafer level chip scale package (WLCSP) or lead frame chip scale package (LFCSP)

ADP8860应用:

Mobile display backlighting

Mobile phone keypad backlighting

Dual RGB backlighting

LED indication

General backlighting of small format displays



图1.ADP8860详细方框图



图2.ADP8860典型应用电路



图3.ADP8860通用应用电路



图4.带键盘光控制的ADP8860应用电路