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

Product

Folder

Sample &

Buy

Technical

Documents

Tools &

Software

Support &

Community

Reference

Design

LM3445

SNVS570M – JANUARY 2009 – REVISED NOVEMBER 2015

LM3445 TRIAC Dimmable Offline LED Driver

1 Features

3 Description

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

1

•

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 1 A

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

•

Low Quiescent Current

capable architecture allows the use of small external

•

Adaptive Programmable Off-Time Allows for

passive components. The LM3445 includes a bleeder

Constant Ripple Current

circuit to ensure proper TRIAC operation by allowing

current flow while the line voltage is low to enable

•

Thermal Shutdown

proper firing of the TRIAC. A passive PFC circuit

•

No 120-Hz Flicker

ensures good power factor by drawing current directly

•

Low Profile 10-Pin VSSOP Package or 14-Pin

from the line for most of the cycle, and provides a

SOIC

constant positive voltage to the buck regulator.

Additional features include thermal shutdown, current

•

Patented Drive Architecture

2 Applications

Device Information(1)

•

Retro Fit TRIAC Dimming

PART NUMBER

PACKAGE

BODY SIZE (NOM)

•

Solid State Lighting

VSSOP (10)

3.00 mm × 3.00 mm

LM3445

•

Industrial and Commercial Lighting

SOIC (14)

3.91 mm × 8.65 mm

•

Residential Lighting

(1) For all available packages, see the orderable addendum at

the end of the data sheet.

Typical LM3445 LED Driver Application Circuit

Efficiency vs Line Voltage

1

An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,

intellectual property matters and other important disclaimers. PRODUCTION DATA.