“This is a high-performance, adjustable constant current, and PWM dimmer project. It provides accurate output constant current and PWM control. The circuit regulates the current flowing through a LED/LED array to maintain the desired level of light output. The board consists of CAT4101 LED driver chip and LTC6992-1 PWM generator chip.
The CAT4101 is a constant-current sink driving a string of high-brightness LEDs up to 1A with a very low dropout of 0.5 V at full load. It requires no inductor, provides a low noise operation, and minimizes the number of components. The LED current is set by an external resistor connected to the RSET pin. The LED pin is compatible with high voltage up to 25 V, allowing the driving of long strings of LEDs. The device ensures an accurate and regulated current in the LEDs independent of supply and LED forward voltage variation. The PWM/EN input allows the device shutdown and the LED brightness adjustment by using an external pulse width modulation (PWM) signal. The driver features thermal shutdown protection that becomes active whenever the die temperature exceeds 150C.
The LTC6992 is a silicon oscillator with an easy-to-use analog voltage-controlled pulse width modulation (PWM) capability. The LTC6992 is part of the Timer Blox® family of versatile silicon timing devices. A single resistor, RSET, programs the LTC6992’s internal master oscillator frequency. The output frequency is determined by this master oscillator and an internal frequency divider, NDIV, programmable to eight settings from 1 to 16384. Applying a voltage between 0V and 1V on the MOD pin sets the duty cycle. The four versions differ in their minimum/maximum duty cycle. Note that a minimum duty cycle limit of 0% or maximum duty cycle limit of 100% allows oscillations to stop at the extreme duty cycle settings.”