IS31LT3938 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 10VDC to 450VDC or
IS31LT3938 incorporates the special feature of three
power sequencing levels by detecting OFF-ON cycles
of the main power switch. When the switch is cycled
within a 4 second period (typical) the device
automatically switches the power level to the next step.
As a result, the input and output power of the luminaire
may be adjusted depending on the desired amount of
illumination and/or power consumption. There are
multiple power levels that the engineer may configure,
2 steps or 3 steps, via the external pins DIM1 and
IS31LT3938 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.
IS31LT3938 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.