8

Pin Descriptions

Pin #

Pin Name

Pin Function

1LX

Collector of the internal power transistor — connect to the boost inductor and rectifying Schottky

diode.

2

EN

Enable and brightness control pin for LED string

3

ISET

Output current set pin — connect a resistor from this pin to GND to set the maximum current.

4

COMP

Output of the internal transconductance error amplifier — this pin is used for loop

compensation and soft-start. Connect a 1.27 Ohm resistor and 47nF capacitor in series to GND.

5

OUT

Boost output voltage monitor pin — internal over-voltage protection monitors the voltage at this

pin. Connect this pin to the output capacitor and the anode of the LED string.

6

BL

LED constant current sink — connect this pin to the cathode of the LED

7

GND

Ground

8

IN

Power supply pin — bypass this pin with a capacitor close to the pin

T

Thermal Pad

Pad for heatsinking purposes — connect to the ground plane using multiple vias.

Not connected internally.

SC4538