V+

BR1

VAC

TRIAC

DIMMER

+

+

1

2

3

4

5

6

7

8

9

10

-

GND

VCC

FLTR2

ASNS

FLTR1

ISNS

GATE

BLDR

COFF

DIM

LM3445MM

D3

C7

C9

C10

D4

D8

D9

R2

D1

Q1

C5

R5

C12

D2

D10

Q2

L2

Q3

R3

R4

C11

C4

C3

R1

U1

95.0

90.0

85.0

80.0

75.0

80

90

100

110

120

130

140

14 Series connected LEDs

10 Series connected LEDs

LM3445

www.ti.com

SNVS570L – JANUARY 2009 – REVISED MAY 2013

Triac Dimmable Offline LED Driver

Check for Samples: LM3445

1

FEATURES

DESCRIPTION

The LM3445 is an adaptive constant off-time AC/DC

2

•

Triac Dim Decoder Circuit for LED Dimming

buck (step-down) constant current controller designed

•

to be compatible with triac dimmers. The LM3445

•

Capable of Controlling LED Currents Greater

provides a constant current for illuminating high

Than 1A

power LEDs and includes a triac dim decoder. The

dim decoder allows wide range LED dimming using

•

Adjustable Switching Frequency

standard triac dimmers. The high frequency capable

•

Low Quiescent Current

architecture allows the use of small external passive

•

Adaptive Programmable Off-Time Allows for

components. The LM3445 includes a bleeder circuit

Constant Ripple Current

to ensure proper triac operation by allowing current

flow while the line voltage is low to enable proper

•

Thermal Shutdown

firing of the triac. A passive PFC circuit ensures good

•

No 120Hz Flicker

power factor by drawing current directly from the line

•

Low Profile 10-Pin VSSOP Package or 14-Pin

for most of the cycle, and provides a constant positive

SOIC

voltage to the buck regulator. Additional features

•

Patent Pending Drive Architecture

under-voltage lockout.

APPLICATIONS

•

Retro Fit Triac Dimming

•

Solid State Lighting

•

Industrial and Commercial Lighting

•

Residential Lighting

Typical LM3445 LED Driver Application Circuit

1

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2

All trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Copyright © 2009–2013, Texas Instruments Incorporated

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.