PPMIC BU

www.belling.com.cn

BL9582 Rev 1.2

Belling Proprietary Information. Unauthorized Photocopy and Duplication Prohibited

2/2010

©2010 Belling All Rights Reserved

11

BL9582

32V, 1.4A Step-down

High Brightness LED Driver with Internal Switch

or applied with a voltage higher than 1.2V

(must be less than or equal to 5V). Actually,

which can be adjusted to a less one by

dimming.

The table below gives values of nominal

average

output

current

for

several

preferred values of current setting resistor

on page 1.

Nominal average output current (mA)

1000

0.1

760

0.13

667

0.15

333

0.3

Output current adjustment by external

DC control

The ADJ pin can be driven by an external

output current to a value below the nominal

U1

BL9582

ADJ

RS

L1

47uH

1

2

D1

1

2

CIN

4.7uF

VADJ

VIN

The average output current is given by:

0.1

(0.3

1.2 )

1.2

ADJ

OUT

ADJ

S

V

I

VV

V

R

×

=≤

≤

×

Note that 100% brightness setting

Output current adjustment by PWM

control

A Pulse Width Modulated (PWM) signal

with duty cycle PWM can be applied to the

ADJ pin, as shown below, to adjust the

output current to a value below the nominal

0.1

(0

100%,1.2

5 )

OUT

ADJ

S

D

I

DV

V

V

R

×

=≤ ≤

≤

≤

0.1

(0

100%, 0.3

1.2 )

1.2

PULSE

OUT

PULSE

S

VD

ID

V

V

V

R

×

×

=≤ ≤

≤

≤

×

U1

BL9582

ADJ

L1

47uH

1

2

RS

D1

1

2

CIN

4.7uF

VIN

PWM

PWM

dimming

provides

reduced

brightness

by

modulating

the

LED’s

forward current between 0% and 100%.

The LED brightness is controlled by

adjusting the relative ratios of the on time

to the off time. A 25% brightness level is

achieved by turning the LED on at full

current for 25% of one cycle. To ensure

this switching process between on and off

state is invisible by human eyes, the

switching frequency must be greater than

100 Hz. Above 100 Hz, the human eyes

average the on and off times, seeing only

an effective brightness that is proportional

to the LED’s on-time duty cycle. The

advantage of PWM dimming is that the

forward

current

is

always

constant,