The CAT4139 is a DC/DC step-up converter that delivers an accurate constant current ideal for driving LEDs. Operation at a fixed switching frequency of 1MHz allows the device to be used with small value external ceramic capacitors and inductor. LEDs connected in series are driven with a regulated current set by the external resistor R1. The CAT4139 is ideal for driving parallel strings of up to five white LEDs in series or up to 22 V.
LED dimming can be done by using a DC voltage, a logic signal, or a pulse width modulation (PWM) signal. The shutdown input pin allows the device to be placed in power-down mode with 'zero' quiescent current.
In addition to thermal protection and overload current limiting, the device also enters a very low power operating mode during 'Open LED' fault conditions.

• Switch Current Limit 750 mA
• Drives LED strings up to 22 V
• Up to 87% Efficiency
• Low Quiescent Ground Current 0.6 mA
• 1 MHz Fixed Frequency Low noise Operation
• Soft start “in-rush” current limiting
• Shutdown current less than 1 µA
• Open LED Overvoltage Protection
• Automatic Shutdown at 1.9 V (UVLO)
• Thermal overload protection