LM3445MM/NOPB National Semiconductor, LM3445MM/NOPB Datasheet
LM3445MM/NOPB
Specifications of LM3445MM/NOPB
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LM3445MM/NOPB Summary of contents
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... Additional features include thermal shutdown, current limit and V der-voltage lockout. Typical LM3445 LED Driver Application Circuit © 2010 National Semiconductor Corporation LM3445 Features ■ Triac dim decoder circuit for LED dimming ■ ...
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Connection Diagrams Top View 10-Pin MSOP NS Package Number MUB10A Ordering Information Order Number Spec. Package Type LM3445MM NOPB MSOP-10 LM3445MMX NOPB MSOP-10 LM3445M NOPB SOIC-14L LM3445MX NOPB SOIC-14L Pin Descriptions SOIC MSOP Name Description 12 1 ASNS PWM output ...
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... Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. BLDR to GND V , GATE, FLTR1 to GND CC ISNS to GND ASNS, DIM, FLTR2, COFF to GND COFF Input Current Continuous Power Dissipation (Note 2) Electrical Characteristics over the full Operating Temperature Range ( T design, or statistical correlation ...
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Symbol Parameter CURRENT SENSE COMPARATOR V FLTR2 open circuit voltage FLTR2 R FLTR2 impedance FLTR2 V Current sense comparator offset voltage OS GATE DRIVE OUTPUT V GATE high saturation DRVH V GATE low saturation DRVL I Peak souce current DRV ...
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Typical Performance Characteristics f vs Input Line Voltage SW BLDR Resistor vs Temperature Min On-Time ( Temperature ON Efficiency vs Input Line Voltage 30060304 V UVLO vs Temperature CC 30060306 Off Threshold (C11) vs Temperature 30060308 5 30060305 ...
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Normalized Variation www.national.com over V Voltage Leading Edge Blanking Variation Over Temperature BUCK 30060310 6 30060372 ...
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Simplified Internal Block Diagram FIGURE 1. Simplified Block Diagram 7 30060311 www.national.com ...
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Application Information FUNCTIONAL DESCRIPTION The LM3445 contains all the necessary circuitry to build a line- powered (mains powered) constant current LED driver whose output current can be controlled with a conventional triac dim- mer. OVERVIEW OF PHASE CONTROL DIMMING A ...
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Theory of Operation Refer to figure 4 below which shows the LM3445 along with basic external circuitry. FIGURE 4. LM3445 Schematic 9 30060301 www.national.com ...
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SENSING THE RECTIFIED TRIAC WAVEFORM A bridge rectifier, BR1, converts the line (mains) voltage (5c) into a series of half-sines as shown in 5b. Figure 5a shows a typical voltage waveform after diode D3 (valley fill circuit ...
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As the holding resistor R5 is in- creased, the overall efficiency per LM3445 will also increase. ANGLE DETECT The Angle Detect circuit uses a comparator with a fixed threshold voltage of 7.21V to monitor the BLDR pin ...
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The valley-fill circuit allows the buck regulator to draw power throughout a larger portion of the AC line. This allows the ca- pacitance needed lower than if there were no BUCK valley-fill circuit, and adds passive ...
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OVERVIEW OF CONSTANT OFF-TIME CONTROL A buck converter’s conversion ratio is defined as: Constant off-time control architecture operates by simply defining the off-time and allowing the on-time, and therefore the switching frequency, to vary as either V The output voltage ...
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... LED driver devices (slaves controlled by a single LM3445 (master) by connecting their DIM pins together. MASTER/SLAVE CONFIGURATION National Semiconductor offers an LM3445 demonstration PCB for customer evaluation through our website. The fol- lowing description and theory uses reference designators that follow our evaluation PCB. The LM3445 Master/Slave schematics are illustrated below (figures 13 - 15) for clarity ...
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MASTER/SLAVE CONNECTION DIAGRAM MASTER/SLAVE BLOCK DIAGRAMS FIGURE 14. Master/Slave configuration with Separate Valley-Fill Circuits FIGURE 13. Master Slave Configuration 15 30060326 30060327 www.national.com ...
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FIGURE 15. Master/Slave configuration with One Valley-Fill Circuit THERMAL SHUTDOWN Thermal shutdown limits total power dissipation by turning off the output switch when the IC junction temperature exceeds www.national.com 165°C. After thermal shutdown occurs, the output switch doesn’t turn on ...
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Design Guide DETERMINING DUTY-CYCLE (D) Duty cycle (D) approximately equals: With efficiency considered: For simplicity, choose efficiency between 75% and 85%. CALCULATING OFF-TIME The “Off-Time” of the LM3445 is set by the user and remains fairly constant as long as ...
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The off-time of the LM3445 can be programmed for switching frequencies ranging from 30 kHz to over 1 MHz. A trade-off between efficiency and solution size must be considered when designing the LM3445 application. The maximum switching frequency attainable is ...
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SETTING THE LED CURRENT The LM3445 constant off-time control loop regulates the peak inductor current (I ). The average inductor current equals the L2 average LED current (I ). Therefore the average LED cur- AVE rent is regulated by regulating ...
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Determining the capacitance value of the valley-fill ca- pacitors: The valley fill capacitors should be sized to supply energy to the buck converter (V ) when the input line is less than its BUCK peak divided by the number of ...
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When the triac is firing at 135° the current through the LED string will be small. Therefore the droop should be small at this point FIGURE 21. AC Line with Various Firing ...
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Design Example The following design example illustrates the process of cal- culating external component values. Known: 1. Input voltage range (90V – 135V AC 2. Number of LEDs in series = 7 3. Forward voltage drop of a single LED ...
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LM3445 Design Example 1 Input = 90V to 135V LED String Application @ 400 mA LED 23 30060369 www.national.com ...
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Bill of Materials Qty Ref Des 1 U1 IC, CTRLR, DRVR-LED, MSOP10 1 BR1 Bridge Rectifiier, SMT, 400V, 800 Common mode filter DIP4NS, 900 mA, 700 1 L2 Inductor, SHLD, SMT, 1A, 470 µH 2 L3, L4 ...
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Physical Dimensions inches (millimeters) unless otherwise noted For Ordering, Refer to Ordering Information Table For Ordering, Refer to Ordering Information Table MSOP-10 Pin Package (MM) NS Package Number MUB10A SOIC-14 Pin Package (M) NS Package Number M14A 25 www.national.com ...
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