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 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 up to 5.5V, 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. The device is housed in a low profile (1mm max height) 5-lead thin SOT23 package for space critical applications.