CAT4237

· Drives 6 to 8 White LEDs in series from 3V
· Up to 87% Efficiency
· Low Quiescent Ground Current 0.6mA
· Adjustable Output Current (up to 40mA)
· High Frequency 1MHz Operation
· High Voltage Power Switch
· Shutdown current less than 1mA
· Open LED low power mode
· Automatic Shutdown at 1.9V (UVLO)
· Thermal shutdown protection
· Thin SOT23 5-Lead (1mm max height)

· Color LCD and keypad Backlighting
· Cellular Phones
· Handheld Devices
· Digital Cameras
· PDAs
· Portable Game Machine

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 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. LED currents up to 40mA can be supported over a wide range of input supply voltages from 2.8V to 5.5V, 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 CAT4237 to be placed in power-down mode with "zero" quiescent current.

In addition to thermal protection and overload current limiting, CAT4237 also enters a very low power operating mode during "Open LED" fault conditions. The device is housed in a low profile (1mm max height) 5-lead thin SOT23 package for space critical applications.