REFERENCE DESIGNS

Three typical LED driving applications are shown.

Firstly a typical LCD backlight circuit, then maximum

brightness LED driving solution and lastly an optimised

battery life LED driving solution.

This application shows the ZXSC310 in a typical LCD

backlight application for Digital Still Cameras and

PDA’s. The input voltage for these backlight circuits are

usually fixed from the main system power, typically

3.3V or 5V. The LED’s are connected serially so that the

light is distributed uniformly in each LED. The current

provided to the LED’s can either be pulsed or DC. The

DC current is programmable via a sense resistor,

for the reference designs. DC current is achieved by

adding a Schottky rectifying diode and an output

capacitor, as shown in the reference design below.

SEMICO NDUC TORS

ZXSC310

ISSUE 3 - SEPTEMBER 2007

6

V

=3.3V/5V

DRIVE

Gnd

S

TDN

LCD backlight circuit

Ref

Value

Part Number

Manufacture

Comments

U1

N/A

ZXSC310E5

Zetex Semiconductors

Single cell converter, SOT23-5

Q1

N/A

FMMT618

Zetex Semiconductors

Low V

D1

N/A

ZHCS1000

Zetex Semiconductors

1A Schottky diode, SOT23

C1

2.2 F

Generic

Various

0805 Size

R1

(6)

150m

Generic

Various

1206 Size

R1

(7)

250m

Generic

Various

1206 Size

L1

(8)

68µH

Surface mount inductor

Materials list

(Notes)