The CAT3644 is a high efficiency fractional charge pump that can drive up to four LEDs programmable by a one wire digital interface. The inclusion of a 1.33x fractional charge pump mode increases device efficiency by up to 10% over traditional 1.5x charge pumps with no added external capacitors. Low noise input ripple is achieved by operating at a constant switching frequency which allows the use of small external ceramic capacitors. The multi-fractional charge pump supports a wide range of input voltages from 2.5 V to 5.5 V. The EN/DIM logic input functions as a chip enable and a digital dimming interface for current setting of all LEDs. Six different current ratios are available via the interface.