WLED charge-pump backlight driver eliminates need for processor for backlighting in portable devices

NORWOOD, USA: Analog Devices Inc. has introduced the ADP8870 white LED charge-pump backlight driver that lowers the power consumption of battery-operated handheld devices by up to 45 percent without compromising viewing quality.

The ADP8870 combines three key functions: a programmable backlight LED charge-pump driver with inputs for a photo transistor to automatically control the LED brightness and a PWM (pulse-width modulation) input to manage the scale of the output current.

This combination of features significantly reduces power use by automatically changing the current intensity based on the ambient lighting levels and the white content of the displayed image. By performing this function automatically, the ADP8870 eliminates the need for a processor to monitor the phototransistor, further reducing power requirements and simplifying the portable backlight design.

“During common operations such as web browsing and email, LED backlighting can account for up to 75 percent of the power used by portable electronics,” said Dan Swan, product line director, Power Regulator Products, Analog Devices.

“The ADP8870 employs ambient light sensing and content-adaptive backlight control techniques that will extend battery life by optimizing the main and sub display and QWERTY keypad lighting.”

The ADP8870 controls up to seven LEDs either grouped together for backlight control or used independently for keypad illumination, indicator lighting or fun lighting1. The fading of each LED is programmable allowing the designer to customize the fade-in, fade-out, dim and off times.