It accepts a supply from 3V to 20V and draws a typical 1.9mA supply current, making it suitable for both primary-side and secondary-side regulation circuits in isolated DC-DC converters, flyback supplies, and telecom bricks.
The 3V to 20V supply range gives flexibility to run from a regulated 3.3V rail or directly off a higher-voltage bias winding without an extra LDO. The 1.9mA supply current is the total current the IC consumes; it is not the LED drive current itself but the control overhead. When sizing the bias supply for the feedback loop, budget this 1.9mA plus the optocoupler LED current (set by the external resistor) to avoid starving the controller during startup or transient load steps.
Housed in a thin SOT-23-6 (TSOT-23-6) package, the LT4430ES6#TRMPBF occupies minimal board area. The six-pin footprint is standard for this family; the thin profile helps in low-profile power supplies.