®

1/8

STLD20D

WHITE LED POWER SUPPLY

PRELIMINARY DATA

October 2004

REV. 2

FEATURES

supply

LEDs branch in shutdown mode

voltage range

current

C8 only)

control

with automatic restart

2.5Vdc to 5Vdc

Table 1: Order Codes

Part Number

Marking

Package

STLD20D-C8

L2D

SOT23-8L

STLD20D-DEF

L2D

QFN 3x3 8L

This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice.

ASD™

Figure 1: Basic connection

L = 10µH

D

Cout = 1µF

Cin = 2.2µF

I

= 20mA

LED

LDS

FB

D: STM BAT20J

L: Murata LQH32CN100K33

SW

GND

(*) STLD20D-C8 only

SHDN

R

(*)

SET

STLD20D

APPLICATION

DESCRIPTION

The STLD20D is a constant switching frequency

boost regulator with specific features to supply up

to 4 white LEDs in series. A stable LED current

regulation, from 2.8V to 4.2V, is achieved by sens-

ing the LED current through a low ohmic shunt re-

includes a supply rejection circuit that prevent any

kind of flickering effect on the display during dy-

namic supply voltage variation. A LED disconnect

switch cut the LED branch to reduce the current

consumption in shutdown mode. The maximum

peak inductor current can be programmed. The

STLD20D includes often numerous features and in-

novative design circuit that allows getting an efficien-

cy above 80% across the total supply voltage range.

Figure 2: Efficiency versus input voltage

78

79

80

81

82

83

84

85

86

87

88

2.5

3

3.5

4

4.5

5

Input voltage (Vdc)

Efficiency (%)