CMOS White LED Driver Boost Converter

• Low quiescent ground current (0.5mA typical)
• Power efficiency over 80%
• Compatible pinout with LT1937
• Adjustable output current (up to 40mA)
• High frequency 1.2MHz operation
• Input voltage operation down to 2.5V
• Low resistance (0.5Ω) power switch
• Drives up to 4 White LEDs in series
• Shutdown current less than 1µA
• Load fault protection against open-circuits
• Low value external components
• Low profile 5-lead SOT23 (1mm max) and TDFN (0.8mm) package

The CAT37 is a DC/DC step up converter that delivers a regulated output current. Operation at a constant switching frequency of 1.2MHz allows the device to be used with very small value external inductor and ceramic capacitors.

The CAT37 is targeted to drive multiple white light-emitting diodes (LEDs) connected in series and provides the necessary regulated current to control the brightness and the color purity. An external resistor R1 controls the output current level. LED currents of up to 40mA can be supported over a wide range of input supply voltages from 2.5V to 7V, making the device ideal for battery-powered applications.

A high voltage output stage allows up to 4 White LEDs to be driven in series. Series drive provides inherent current matching.

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 "near zero" quiescent current.

In addition to overcurrent limiting protection, the device also includes detection circuitry to ensure protection against open-circuit load fault conditions.

The device is available in a low profile (1mm max height) 5-lead thin SOT23 package.

• Color LCD and keypad backlighting
• Cellular phones
• Handheld terminals
• Digital cameras
• PDAs/Games
• Portable MP3 players