Demonstration Circuit DC688 is a quad output power supply intended for use in small to medium size TFT panels. The circuit features the LT1942 quad output switching regulator and generates an LED driver along with the triple output supply required for the TFT panels. With an input voltage range of 3V to 4.2V, two step-up regulators and one inverting regulator provide AVDD , VON and VOFF bias voltages for the LCD panels. Another high power boost is used to drive 12 LEDs (2 strings of 6 LEDs each). For 3V minimum input voltage, up to 20mA current is available for each LED string. A built-in LED ballast circuit is included to precisely match the LED currents in the two strings.