LX1994

Microsemi

Integrated Products Division

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

Page 8

High Efficiency LED Driver

Copyright

© 2003

Rev. 1.0a, 2004-08-10

TM

®

APPLICATION CIRCUITS

VDD

VSS

SNK

SRC

LX1970

AUTO

DRV

SRC

OVP

S/P

VIN

BRT

V

GND

LX1994

FB

33uH

FDV303

UPS5819

LS

CMP

0.1uF

R5

R6

R7

PWM

C2

R4

R1

R2

R3

100% DUTY

80% DUTY

60% DUTY

40% DUTY

20% DUTY

0% DUTY

AUTO MODE RESPONSE

LED

CURRENT

AMBIENT LIGHT

MAX

1M

30k

15

2.94k

28.7k

226k

23.2k

1uF

C1

22uF

Figure 2 –PWM Dimming applied to S/P Input and Light Sensor (Dimming option 1)

100% DUTY

80% DUTY

60% DUTY

40% DUTY

20% DUTY

0% DUTY

AUTO MODE RESPONSE

LED

CURRENT

AMBIENT LIGHT

MAX

VDD

VSS

SNK

SRC

LX1970

AUTO

DRV

SRC

OVP

S/P

VIN

BRT

V

GND

LX1994

FB

33uH

FDV303

UPS5819

LS

CMP

0.1uF

R5

R6

R7

PWM

C2

R4

C1

R1

R2

R3

1M

30k

15

2.94k

28.7k

226k

4.99k

100uF

1uF

1M

Vcc

110k

BSS123

+

-

Figure 3 –PWM Dimming applied to S/P Input and Light Sensor (Dimming option 2)