The LM3445 is an adaptive constant off-time AC/DC buck
(step-down) constant current controller designed to be compatible
with triac dimmers. The LM3445 provides a constant
current for illuminating high power LEDs and includes a triac
dim decoder. The dim decoder allows wide range LED dimming
using standard triac dimmers. The high frequency capable
architecture allows the use of small external passive
components. The LM3445 includes a bleeder circuit to ensure
proper triac operation by allowing current flow while the line
voltage is low to enable proper firing of the triac. A passive
PFC circuit ensures good power factor by drawing current directly
from the line for most of the cycle, and provides a
constant positive voltage to the buck regulator. Additional
features include thermal shutdown, current limit and VCC under-
voltage lockout.