W-52

2

Typical Application Circuit

Figure 1. Li Ion Driver for Four High Brightness White LEDs

15 mA

4

1.50 k

TSOT 23 Pin Numbers

6.8 H

2

3

1

6

5

SW

VIN

RSET

D1

C2

1 F

C1

4.7 F

VIN

2.7 V

to

4.2 V

PWM

DIMMING

CONTROL

W-52

LED

GND

SHDN

C1: Taiyo Yuden JMK212BJ475

C2: Taiyo Yuden EMK212BJ105

D1: Zetez ZHCS400

L1: Sumida CLQ4D106R8

(Panasonic ELJEA6R8)

Table 1. PIN DESCRIPTION

Pin Number

SOT23

Name

Function

1

SW

Switch pin. This is the drain of the internal power switch. For minimum EMI, min-

imize the trace area connected to this pin.

2

GND

Ground pin. Connect pin 2 to ground.

3

LED

LED (cathode) connection pin.

4

RSET

RESET pin. A resistor connected from pin 4 to ground sets the LED current. This

pin is also used to dim the LEDs.

5

SHDN

Shutdown pin.

6

VIN

Input supply pin. This pin should be bypassed with a capacitor to ground. A

4.7 F capacitor mounted close to the pin is recommended.