A8600

AiT Semiconductor Inc. www.ait-ic.com   A8600 WHITE LED BACKLIGHT DRIVER SIX-STRING WITH ACTIVE CURRENT   DESCRIPTION The A8600 is a high-efficiency driver for white light-emitting diodes (LED(s)). It is designed for large liquid-crystal displays (LCD(s)) that employ an array of LED(s) as the light source. A current-mode step-up controller drives up to six parallel strings of multiple series-connected LED(s). Each string is terminated with ballast that achieves ±1.5% current regulation accuracy, ensuring even bright-ness for all LED(s). The A8600 has a wide input-voltage range from 4.5V to 26V, and provides a fixed 20mA or adjustable 15mA to 25mA full-scale LED current. The A8600 has two dimming control modes to enable a wide variety of applications. In direct DPWM mode, the LED current is directly turned on and off by a PWM signal. In analog dimming mode, an internal phase-locked loop (PLL) circuit translates the PWM signal into an analog signal and linearly controls the LED current down to 12.5%. Below 12.5%, digital dimming is added to allow lower average LED current down to 1%. Both control methods provide 100:1 dimming range. The A8600 has multiple features to protect the controller from fault conditions. Separate feedback loops limit the output voltage if one or more LED(s) fail open or short. The controller features cycle-by cycle current limit to provide consistent operation and soft-start capability. A thermal shutdown circuit provides another level of protection. ...