The LT?3755 and LT3755-1 are DC/DC controllers designed
to operate as a constant-current source for driving high
current LEDs. They drive a low side external N-channel
power MOSFET from an internal regulated 7V supply. The
??? xed frequency, current-mode architecture results in stable
operation over a wide range of supply and output voltages.
A ground referenced voltage FB pin serves as the input for
several LED protection features, and also makes it possible
for the converter to operate as a constant-voltage source.
A frequency adjust pin allows the user to program the
frequency from 100kHz to 1MHz to optimize ef?? ciency,
performance or external component size.
The LT3755/LT3755-1 sense output current at the high
side of the LED string. High side current sensing is the
most ?? exible scheme for driving LEDs, allowing boost,
buck mode or buck-boost mode con?? guration. The PWM
input provides LED dimming ratios of up to 3000:1, and
the CTRL input provides additional analog dimming ca-
pability. Both parts are available in the 16-lead (3mm ×
3mm) QFN package.