ZXSC300

ISSUE 4 - SEPTEMBER 2007

9

Output Power Calculation

By making the above assumptions for inductance and

peak current the output power can be determined by:

P

(V

V

x I

I

OUT

OUT

IN

PK

MIN

=

+

)(

)

2

x

T

TT

OFF

ON

OFF

()

+

drop

where

≅ 1.7µs (internally set by ZXSC300)

and

T

TV

V

V

ON

OFF

OUT

IN

IN

=

−

()

and

II

(V

- V

xT

L

MIN

PK

OUT

IN

OFF

=−

)

Operating f requency c an be derived by:

F

TT

ON

OFF

=

+

1

()

Capacitor selection

For pulsed operation, as in the maximum battery life

solution, no capacitors are required at the output to

the LED. For rectified operation, as in the maximum

brightness solution, a small value ceramic capacitor

is required, typically 2.2uF.

Generally an input capacitor is not required, but a

small ceramic capacitor may be added to aid EMC,

typically 470nF to 1uF.

Demonstration board

A demonstration board for the Maximum battery life

solution, is available upon request. These can be

obtained through your local Zetex office or through

Zetex web pages. For all reference designs Gerber

files and bill of materials can be supplied.

Layout of Maximum battery life solution

Top Copper

Drill Holes

Bottom Copper

Silk Screen