SNVS570M January   2009  – November 2015 LM3445

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Overview of Phase Control Dimming
      2. 7.3.2  Theory of Operation
      3. 7.3.3  Sensing the Rectified TRIAC Waveform
      4. 7.3.4  LM3445 Line Sensing Circuitry
      5. 7.3.5  TRIAC Holding Current Resistor
      6. 7.3.6  Angle Detect
      7. 7.3.7  Bleeder
      8. 7.3.8  FLTR1 Pin
      9. 7.3.9  Dim Decoder
      10. 7.3.10 Valley-Fill Circuit
      11. 7.3.11 Valley-Fill Operation
      12. 7.3.12 Buck Converter
      13. 7.3.13 Overview of Constant Off-Time Control
      14. 7.3.14 Master/Slave Operation
      15. 7.3.15 Master/Slave Configuration
      16. 7.3.16 Master Board Modifications
      17. 7.3.17 Slave Board Modifications
      18. 7.3.18 Master/Slave Interconnection
      19. 7.3.19 Master/Slave Theory of Operation
      20. 7.3.20 Master/Slave Connection Diagram
      21. 7.3.21 Master/Slave Block Diagrams
      22. 7.3.22 Thermal Shutdown
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Determining Duty-Cycle (D)
      2. 8.1.2 Calculating Off-Time
      3. 8.1.3 Setting the Switching Frequency
      4. 8.1.4 Inductor Selection
      5. 8.1.5 Setting the LED Current
      6. 8.1.6 Valley Fill Capacitors
        1. 8.1.6.1 Determining the Capacitance Value of the Valley-Fill Capacitors
        2. 8.1.6.2 Determining Maximum Number of Series Connected LEDs Allowed
      7. 8.1.7 Output Capacitor
      8. 8.1.8 Switching MOSFET
      9. 8.1.9 Re-Circulating Diode
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curve
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Community Resources
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

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6 Specifications

6.1 Absolute Maximum Ratings

See(1) (3)(2)
MIN MAX UNIT
BLDR to GND –0.3 17 V
VCC, GATE, FLTR1 to GND –0.3 14 V
ISNS to GND –0.3 2.5 V
ASNS, DIM, FLTR2, COFF to GND –0.3 7 V
COFF Input Current 100 mA
Continuous Power Dissipation(4) Internally Limited
Junction Temperature (TJ-MAX) 150 °C
Storage Temperature –65 150 °C
(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability
(2) All voltages are with respect to the potential at the GND pin, unless otherwise specified.
(3) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and specifications.
(4) Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ = 165°C (typ.) and disengages at +TJ = 145°C (typ).

6.2 ESD Ratings

VALUE UNIT
V(ESD) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1)(3) ±2000 V
Charged-device model (CDM), per JEDEC specification JESD22-C101(2) ±1000
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
(2) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
(3) Human Body Model, applicable std. JESD22-A114-C.

6.3 Recommended Operating Conditions

MIN MAX UNIT
VCC 8 12 V
Junction Temperature –40 125 °C

6.4 Thermal Information

THERMAL METRIC(1) LM3445 UNIT
DGS (VSSOP) D (SOIC)
10 PINS 14 PINS
RθJA Junction-to-ambient thermal resistance 159 82.8 °C/W
RθJC(top) Junction-to-case (top) thermal resistance 54.5 40.2 °C/W
RθJB Junction-to-board thermal resistance 78.7 37.5 °C/W
ψJT Junction-to-top characterization parameter 5.3 6.4 °C/W
ψJB Junction-to-board characterization parameter 77.5 37.2 °C/W
RθJC(bot) Junction-to-case (bottom) thermal resistance N/A N/A °C/W
(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report, SPRA953.

6.5 Electrical Characteristics

All Typical limits are for TJ = 25°C and all Maximum and Minimum limits apply over the full Operating Temperature Range ( TJ = −40°C to +125°C). Minimum and Maximum limits are specified through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = +25ºC, and are provided for reference purposes only.
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
BLEEDER
RBLDR Bleeder resistance to GND IBLDR = 10 mA 230 325 Ω
VCC SUPPLY
IVCC Operating supply current 2 2.85 mA
VCC-UVLO Rising threshold 7.4 7.7 V
Falling threshold 6 6.4
Hysterisis 1
COFF
VCOFF Time out threshold 1.225 1.276 1.327 V
RCOFF Off timer sinking impedance 33 60 Ω
tCOFF Restart timer 180 µs
CURRENT LIMIT
VISNS ISNS limit threshold 1.174 1.269 1.364 V
tISNS Leading edge blanking time 125 ns
Current limit reset delay 180 µs
ISNS limit to GATE delay ISNS = 0 to 1.75-V step 33 ns
INTERNAL PWM RAMP
fRAMP Frequency 5.85 kHz
VRAMP Valley voltage 0.96 1 1.04 V
Peak voltage 2.85 3 3.08
DRAMP Maximum duty cycle 96.5% 98%
DIM DECODER
tANG_DET Angle detect rising threshold Observed on BLDR pin 6.79 7.21 7.81 V
VASNS ASNS filter delay 4 µs
ASNS VMAX 3.85 4 4.15 V
IASNS ASNS drive capability sink VASNS = 2 V 7.6 mA
ASNS drive capability source VASNS = 2 V –4.3
DIM low sink current VDIM = 1 V 1.65 2.8
DIM High source current VDIM = 4 V –4 –3
VDIM DIM low voltage PWM input voltage threshold 0.9 1.33 V
DIM high voltage 2.33 3.15
VTSTH Tri-state threshold voltage Apply to FLTR1 pin 4.87 5.25 V
RDIM DIM comparator tri-state impedance 10 MΩ
CURRENT SENSE COMPARATOR
VFLTR2 FLTR2 open circuit voltage 720 750 780 mV
RFLTR2 FLTR2 impedance 420 kΩ
VOS Current sense comparator offset voltage –4 0.1 4 mV
GATE DRIVE OUTPUT
VDRVH GATE high saturation IGATE = 50 mA 0.24 0.5 V
VDRVL GATE low saturation IGATE = 100 mA 0.22 0.5
IDRV Peak souce current GATE = VCC/2 –0.77 A
Peak sink current GATE = VCC/2 0.88
tDV Rise time Cload = 1 nF 15 ns
Fall time Cload = 1 nF 15
THERMAL SHUTDOWN
TSD Thermal shutdown temperature See  (1) 165 °C
Thermal shutdown hysteresis 20
(1) Junction-to-ambient thermal resistance is highly application and board-layout dependent. In applications where high maximum power dissipation exists, special care must be paid to thermal dissipation issues in board design. In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = 125°C), the maximum power dissipation of the device in the application (PD-MAX), and the junction-to ambient thermal resistance of the part/package in the application (RθJA), as given by the following equation: TA-MAX = TJ-MAX-OP – (RθJA × PD-MAX).

6.6 Typical Characteristics

LM3445 30060304.gif Figure 1. fSW vs Input Line Voltage
LM3445 30060306.gif Figure 3. BLDR Resistor vs Temperature
LM3445 30060308.gif Figure 5. Min On-Time (tON) vs Temperature
LM3445 30060310.gif Figure 7. Normalized Variation in fSW over VBUCK Voltage
LM3445 30060305.gif Figure 2. Efficiency vs Input Line Voltage
LM3445 30060307.gif Figure 4. VCC UVLO vs Temperature
LM3445 30060309.gif Figure 6. Off Threshold (C11) vs Temperature
LM3445 30060372.gif Figure 8. Leading Edge Blanking Variation Over Temperature