The CAT4238 is a DC-DC step-up converter that delivers an accurate constant current ideal for driving LEDs. Operation at a fixed 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 up to 5.5 V, making the device ideal for battery-powered applications. The CAT4238 high-voltage output stage is perfect for driving mid-size and large panel displays containing up to ten white LEDs in series.
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 High Voltage LED strings (38 V)
• Up to 87% Efficiency
• Low Quiescent Ground Current 0.6 mA
• Adjustable Output Current
• 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
• Mid-size and Large Panel Displays