Triac Dimmable Offline LED Driver - LM3445

LM3445 (ACTIVE)

Triac Dimmable Offline LED Driver

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 VCC under-voltage lockout.

Features

  • Triac Dim Decoder Circuit for LED Dimming
  • Application Voltage Range 80VAC – 277VAC
  • 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

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Input Voltage (Type)
Vin (Min) (V)
Vin (Max) (V)
Iout (Max) (A)
Vout (Min) (V)
Vout (Max) (V)
Regulated Outputs (#)
Topology
Dimming Method
Power Factor Correction (Min)
Type
Switching Frequency (Min) (kHz)
Switching Frequency (Max) (kHz)
Iq (Typ) (mA)
Vref (V)
UVLO Thresholds On/Off (V)
Special Features
Rating
Operating Temperature Range (C)
Pin/Package
Approx. Price (US$)
LM3445 LM3447
AC/DC     AC/DC    
8     7.5    
12     17.5    
2     2    
9     9    
60     60    
1     1    
Buck
Flyback    
Flyback    
Analog
Forward Phase (Triac)
PWM
Reverse Phase    
Forward Phase (Triac)
Reverse Phase    
Active
Passive    
Active    
Inductive     Inductive    
30     60    
1000     120    
2     1.6    
0.75     1    
7.4 / 6.4     10.5 / 7.5    
Adjustable Switch Frequency
Enable/Shutdown
Thermal Shutdown    
Adjustable Switch Frequency
Soft Switching
Thermal Shutdown    
Catalog     Catalog    
-40 to 125     -40 to 125    
10VSSOP
14SOIC    
14TSSOP    
0.60 | 1ku     0.65 | 1ku    
WEBENCH® LM3445
 
110.00 <=


V in Lower
 V
 
<=


V in Upper
 V
 
<= 270.00
Ambient Temp  °C <= 100
Light Output (optional)  Lumens



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