The CAT3661 is a high efficiency low power fractional charge pump that drives one LED with up to 5 mA of current. Soft-start current limiting and short-circuit protection are optimized for use with coin cell batteries.Low noise input ripple and constant switching frequency allows the use of small external ceramic capacitors. This makes the CAT3661 ideal for EMI sensitive applications. The charge pump supports a wide range of input voltages from 2.0 V to 5.5 V.The CAT3661 has a built-in circuitry to provide feedback to a microcontroller of Open/Short LED and Low battery events. The Low battery indicator trip point is internally fixed at 2.4 V. External resistors can be added to raise or lower the trip voltage, if needed.The device is packaged in the tiny 16-lead TQFN 3 mm x 3 mm package with a max height of 0.8 mm.The inclusion of a 1.33x fractional charge pump mode increases device efficiency by up to 10% over traditional 1.5x tri-mode charge pumps with no added external capacitors.