The CAT4240 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. The CAT4240 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
The CAT4240 is a 6 W boost LED driver that delivers a constant current up to 750 mA for high‑voltage LED strings (up to 38 V). It operates at a fixed 1 MHz switching frequency, offering up to 94 % efficiency and very low quiescent current.
The device includes built‑in protections such as UVLO at 1.9 V, shutdown current below 1 pA, thermal overload shutdown at 150 °C, and an open‑LED over‑voltage protection that limits the output to 42 V. Recommended external components include a 47 µH inductor (e.g., Sumida CDRH6D28‑470) and a Schottky diode (e.g., CMSH1‑40).
| Switch Current Limit | 750 mA |
|---|---|
| Efficiency | up to 94 % |
| Quiescent Ground Current | 0.6 mA |
| Shutdown Current | < 1 pA |
| UVLO Threshold | 1.9 V |
| Supply Voltage Range | 2.8 V – 5.5 V |
| Switching Frequency | 1 MHz |
| Maximum Duty Cycle | 92 % |
| Thermal Shutdown Temperature | 150 °C |
| Thermal Hysteresis | 20 °C |
The device can limit the switch current to 750 mA.
LED current is set by an external resistor R1 using the formula I_LED = 0.3 V / R1.
The device shuts down when the voltage exceeds 1.9 V (UVLO).