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NJU6052

Ver.2004-02-26

(9) APPLICATIONS INFORMATION

(9-1)

PWM DUTY and LED CURRENT

Formula (4).

(9-2)

INDUCTOR SELECTION

Formula (5) is used to choose an optimum inductor, as shown below:

η

: Power conversion efficiency (= 0.7 to 0.8)

VDS

(9-3)

DIODE SELECTION

A Schottky diode with a low forward-voltage-drop and a fast switching-speed is ideal. And the diode must

have a rating greater than the output voltage and the output current in the system.

(9-4)

CAPACITOR SELECTION

A low ESR (Equivalent Series Resistance) capacitor should be used at the output to minimize output ripples. A

multi-layer ceramic capacitor is the best selection for the NJU6052 application because of not only the low ESR

but its small package. A ceramic capacitor as the input decoupling-capacitor is also recommended and should be

placed as close to the NJU6052 as possible.

LED

REF

R

V

DUTY

=

⋅

=

LED(max)

LED(max)

LED(avg)

I

100

I

I

--- Formula (4)

DELAY

DS

(max)

IN

LIMIT

PEAK

,

L

T

L

V

V

I

I

⋅













−

+

=

OSC

LIMIT

LED

IN

OUT

f

I

I

V

V

L

⋅

⋅













−

=

2

2

η

--- Formula (5)

--- Formula (6)