The CAT3649 is a high efficiency fractional charge pump that can drive up to six LEDs. The inclusion of a 1.33x fractional charge pump mode increases the 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 2.4 V to 5.5 V.
The LED current can be adjusted in different ways. The full-scale LED current is set to 25 mA once the device is enabled. Analog dimming in 32 linear steps is achieved via a 1-wire pulse-dimming input (ADIM). Further adjustment of the LED current can be done by applying a pulse width modulation (PWM) signal on the PWM input. The PWM dimming control is compatible with content adaptive brightness control (CABC) for a wide range of PWM signal frequency up to 200 kHz.
The CAT3649 can be shut down by holding the ADIM or PWM input in a logic low condition for greater than 30 ms.

• High Efficiency 1.33x Charge Pump
• Drives up to 6 LEDs at 25 mA Each
• PWM Dimming 100 Hz to 200 kHz for CABC
• Quad-mode Charge Pump: 1x, 1.33x, 1.5x, 2x
• 1-wire EZDim
• 32 Linear Steps (ADIM)
• Power Efficiency up to 92%
• Low Noise Input Ripple in All Modes
• Zero Current Shutdown Mode
• Soft Start and Current Limiting
• Short Circuit Protection
• Thermal Shutdown Protection