The CAT4237 is a DC-DC step-up converter that delivers an accurate constant current ideal for driving LEDs. Operation at a constant switching frequency of 1 MHz 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. LED currents up to 40 mA can be supported over a wide range of input supply voltages from 2.8 V to 5.5 V, making the device ideal for battery-powered applications. The CAT4237 high-voltage output stage is perfect for driving six, seven or eight white LEDs in series with inherent current matching in LCD backlight applications.
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.

• Drives 6 to 8 White LEDs in series from 3 V
• Up to 87% efficiency
• Low Quiescent Ground Current 0.6 mA
• Adjustable Output Current (up to 40 mA)
• High Frequency 1 MHz Operation
• High Voltage Power Switch
• Shutdown current less than 1 µA
• Open LED low power mode
• Automatic Shutdown at 1.9 V (UVLO)
• Thermal shutdown protection
• Digital Still Cameras