Charge Pump Regulator
Tue, 08/03/2004 - 5:13am
The ADM8845 from Analog Devices provides the power required to drive up to six white LEDs from a 2.6 to 5.5 V (Li-Ion) input supply, using charge pump technology. The white LEDs are used for backlighting a color LCD display. To maximize power efficiency, a charge pump that can operate in either of a 1x, 1.5x, or 2x mode is used. The charge pump automatically switches between 1x/1.5x/2x modes based on the input voltage, to maintain correct output levels at a high power efficiency. Improved brightness matching of the white LEDs is achieved by the use of a feedback pin to sense individual LED current with a maximum matching accuracy of 1% and ISET to ILED maximum matching of 1%.