LM3445_15 Datasheet, PDF (1/42 Pages) Texas Instruments – TRIAC Dimmable Offline LED Driver

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LM3445
SNVS570M – JANUARY 2009 – REVISED NOVEMBER 2015
LM3445 TRIAC Dimmable Offline LED Driver
1 Features
•1 TRIAC Dim Decoder Circuit for LED Dimming
• Application Voltage Range 80 V_AC to 277 V_AC
• Capable of Controlling LED Currents Greater
Than 1 A
• Adjustable Switching Frequency
• Low Quiescent Current
• Adaptive Programmable Off-Time Allows for
Constant Ripple Current
• Thermal Shutdown
• No 120-Hz Flicker
• Low Profile 10-Pin VSSOP Package or 14-Pin
SOIC
• Patented Drive Architecture
2 Applications
• Retro Fit TRIAC Dimming
• Solid State Lighting
• Industrial and Commercial Lighting
• Residential Lighting
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
VBUCK
VLED
C12
-
R4
VLED-
D10
Q3
L2
ICOLL
Q2
4 COFF
ISNS ⁷
5 FLTR2
GND 6
R3
C4
3 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.
Device Information⁽¹⁾
PART NUMBER
PACKAGE
BODY SIZE (NOM)
LM3445
VSSOP (10)
SOIC (14)
3.00 mm × 3.00 mm
3.91 mm × 8.65 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Efficiency vs Line Voltage
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
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.