IS31LT3918 LED driver IC is a peak current detection
buck converter which operates in constant off time
mode. It operates over a very wide input voltage supply
range of 6VDC to 450VDC or 110VAC/220VAC.
IS31LT3918 incorporates the special feature of switch
dimming by detecting OFF-ON cycles of the main
power switch. When the switch is cycled within a 2
second period (typical) the device automatically
switches the dimming level to the next step. As a result,
dimming can be achieved without replacing any wiring
in the original system. There are multiple modes of
switch dimming that the user may configure 2 steps or
3 steps, as well as different levels of dimming via the
external pins DIM1 and DIM2.
IS31LT3918 can also realize LED dimming using an
external PWM signal. It can accept a PWM signal from
0% to 100% duty cycle. The LED current may also be
adjusted linearly by applying an analog input voltage in
the range of 0.5V to 2.5V.
IS31LT3918 adopts a peak current mode control
architecture, which eliminates the need for any
additional loop compensation while maintaining a good
degree of constant output current regulation.