LM3445_14 Datasheet, PDF (1/37 Pages) Texas Instruments – Triac Dimmable Offline LED Driver

LM3445
www.ti.com
SNVS570K – JANUARY 2009 – REVISED NOVEMBER 2011
Triac Dimmable Offline LED Driver
Check for Samples: LM3445
FEATURES
1
•2 Triac Dim Decoder Circuit for LED Dimming
• Application Voltage Range 80V_AC – 277V_AC
• Capable of Controlling LED Currents Greater
Than 1A
• Adjustable Switching Frequency
• Low Quiescent Current
• Adaptive Programmable Off-Time Allows for
Constant Ripple Current
• Thermal Shutdown
• No 120Hz Flicker
• Low Profile 10-Pin VSSOP Package or 14-Pin
SOIC
• Patent Pending Drive Architecture
APPLICATIONS
• Retro Fit Triac Dimming
• Solid State Lighting
• Industrial and Commercial Lighting
• Residential Lighting
DESCRIPTION
The LM3445 is an adaptive constant off-time AC/DC
buck (step-down) constant current controller designed
to be compatible with triac dimmers. The LM3445
provides a constant current for illuminating high
power LEDs and includes a triac dim decoder. The
dim decoder allows wide range LED dimming using
standard triac dimmers. The high frequency capable
architecture allows the use of small external passive
components. The LM3445 includes a bleeder circuit
to ensure proper triac operation by allowing current
flow while the line voltage is low to enable proper
firing of the triac. A passive PFC circuit ensures good
power factor by drawing current directly from the line
for most of the cycle, and provides a constant positive
voltage to the buck regulator. Additional features
include thermal shutdown, current limit and V_CC
under-voltage lockout.
TYPICAL LM3445 LED DRIVER APPLICATION CIRCUIT
BR1
TRIAC
DIMMER
VAC
V+
R2
D1
D3
C7 ⁺
D4
D9
C10
D8 _{C9 +}
Q1
D2
R5
C5
LM3445MM
1 ASNS _U1 BLDR 10
R1
2 FLTR1
VCC 9
C3
3 DIM
GATE ⁸
4 COFF
ISNS ⁷
5 FLTR2
GND 6
C4
VBUCK
VLED
C12
-
R4
VLED-
D10
Q3
L2
ICOLL
Q2
R3
95.0
14 Series connected LEDs
90.0
85.0
10 Series connected LEDs
80.0
75.0
80
90 100 110 120 130 140
LINE VOLTAGE (V_AC)
C11
1
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2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2009–2011, Texas Instruments Incorporated