CAT4106 constant current white LED driver
Using the CAT4106 integrated multi-channel LED driver and high power dc-dc converter manufactured by ON Semiconductor can be designed a very simple and high efficacy LED driver suitable for powering backlighting applications up to a total of 6 watts.
Up to four matched LED strings can be accurately programmed with uniform drive current set by a single external resistor.
The CAT4106 driver automatically adjusts the output voltage to drive the highest forward voltage string with the minimum headroom voltage maximizing the efficiency.
External programming resistors set the minimum and maximum voltage limits for the acceptable 'window of operation' for LED strings. Any channel which fails to regulate within the window (Open or Short LED) is detected and flagged on the FAULT logic output (active low, open-drain).
This constant current white LED driver based on CAT4106 requires small ceramic capacitors of 1 μF on the VIN pin (C1), 4.7 μF on the inductor input (C2), and 10 μF on the output (C3). Under normal condition, a 4.7 μF input capacitor (C2) is sufficient.
A 47 μH inductor is recommended with current rating of 1 A or higher and 1A rated Schottky diode .
A typical value for resistor R7 and R5 is around 20 kΩ. R6 and R4 can be calculated as follows: