This 4 channel LED driver circuit is designed using CAT4106 integrated LED driver (multi-channel LED driver) and high power dc-dc converter suitable for powering backlighting applications up to a total of 6 watts.
Up to 4 matched LED strings can be accurately programmed with uniform drive current set by a single external resistor.
The CAT4106 4 channel LED driver circuit automatically adjusts the output voltage to drive the highest forward voltage string with the minimum headroom voltage maximizing the efficiency.
High resolution dimming control is achieved by the EN/PWM logic pin which supports multiple frequencies.
This ensures precise PWM dimming control while the device remains fully biased. In addition, when held at logic low, the device to enter a full shutdown 'zero' current mode.
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).
The 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: