The IS31LT3380 is a continuous mode inductive
step-down converter, designed for driving a single LED or
multiple series connected LEDs efficiently from a voltage
source higher than the LED voltage. The chip operates
from an input voltage between 8.5V and 40V and
provides an output current up to 1.2A.
The IS31LT3380 includes a high-side output current
sensing circuit, which uses an external resistor to set the
nominal average output current. The IS31LT3380
includes an integrated output switch which has a very low
conducting impedance to ensure high system efficiency.
The IS31LT3380 has switch dimming function. The chip
detects external switch action to adjust output current,
allowing for dimming functionality to be achieved without
changing the original lighting system circuitry.
The switch dimming is implemented in either two-level
mode or three-level mode. The output current of every
level and the total number of levels are customer
selected by setting the corresponding input conditions of
DIM1 and DIM2 pin.
The output current is set at the initial value the first time
that power is supplied to the chip. After the initial power
up sequence, the chip adjusts the output current
according to the external switch action. After the lowest
current level, the current cycles back to the initial value if
more switch action is detected. If the power is switched
off for longer than 2 seconds, the device will return to it’s
initial state, and the output current will be set to the initial
value at the next time that power is applied.