LM3445 Triac dimmable offline LED driver | TI.com

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Triac dimmable offline LED driver

Triac dimmable offline LED driver - LM3445


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.


  • TRIAC Dim Decoder Circuit for LED Dimming
  • Application Voltage Range 80 VAC to 277 VAC
  • 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
  • Patented Drive Architecture


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Part number Order 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) Features Operating temperature range (C) Package Group Package size: mm2:W x L (PKG)
LM3445 Order now AC/DC     8     12     2     9     60     1     Buck
Forward Phase (Triac)
Reverse Phase    
Inductive     30     1000     2     0.75     7.4 / 6.4     Adjustable Switch Frequency
Thermal Shutdown    
-40 to 125     SOIC | 14
VSSOP | 10    
14SOIC: 52 mm2: 6 x 8.65 (SOIC | 14)
10VSSOP: 9 mm2: 3 x 3 (VSSOP | 10)    
LM3447 Order now AC/DC     7.5     17.5     2     9     60     1     Flyback     Forward Phase (Triac)
Reverse Phase    
Active     Inductive     60     120     1.6     1     10.5 / 7.5     Adjustable Switch Frequency
Soft Switching
Thermal Shutdown    
-40 to 125     TSSOP | 14     14TSSOP: 32 mm2: 6.4 x 5 (TSSOP | 14)