Four White LED Backlight Driver
The ADM8843 uses charge pump technology to provide the power to drive up to four LEDs. The LEDs are used for backlighting a color LCD display that has regulated constant current for uniform brightness intensity. The main display can use up to three LEDs, and the sub display uses one LED. The CTRL1 and CTRL2 digital input control pins control the shutdown operation and the brightness of the main and sub displays.
To maximize power efficiency, the charge pump can operate in 1×, 1.5×, or 2× mode. The charge pump automatically switches among 1×/1.5×/2× modes, based on the input voltage, to maintain sufficient drive for the LED anodes at the highest power efficiency.
Improved brightness matching of the LEDs is achieved by a feedback pin that senses individual LED current with a typical matching accuracy of 0.3%.
- Cellular phones with main and sub displays
- White LED backlighting
- Camera flash/strobes and movie light applications
- Micro TFT color displays
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
The ADM8843 provides two digital input control pins, CTRL1 and CTRL2, which control the operation and the brightness of the LEDs. The ADM8843 is configured with a sub and main display, the main display refers to 3 of the 6 LEDs (FB1 – FB3) and the sub display refers to the remaining LED (FB54).
The ADM8843 provides the option to control the brightness of the LEDs with a digital PWM signal. The duty cycle of the PWM signal determines the brightness of the backlight LEDs. Brightness control of the LEDs can also be controlled by a DC voltage. The ADM8843 has soft-start circuitry to limit inrush current flow at power up.
The ADM8843 is fabricated using CMOS technology for minimal power consumption. The part is packaged in a 16-lead LFCSP (Lead Frame Chip Scale Package).
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