LM3445-208277EV/NOPB National Semiconductor, LM3445-208277EV/NOPB Datasheet
LM3445-208277EV/NOPB
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LM3445-208277EV/NOPB Summary of contents
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... Simplified LM3445 Schematic and Efficiency Plot Warning: This LM3445 evaluation PCB is a non-isolated design. The ground connection on the evaluation board is NOT referenced to earth ground oscilloscope ground lead is connected to the evaluation board ground test point for analysis, and AC power is applied, the fuse (F1) will fail open. ...
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... Pull above 4.9V (typical) to TRI-STATE 3 DIM Input/output dual function dim pin. This pin can be driven with an external PWM signal to dim the LEDs. It may also be used as an output signal and connected to the DIM pin of other LM3445 or LED drivers to dim multiple LED circuits simultaneously. 4 COFF OFF time setting pin ...
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... LM3445 Evaluation Board Schematic 30103508 3 www.national.com ...
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... Bill of Materials LM3445 Evaluation Board REF DES Description U1 IC Driver LED W/TRIAC DIM 10MSOP BR1 Bridge Rectifier 600V 0.8A MINIDIP X7R 1206 10% 500V Ceramic C2 330V AC C3, C23, C35 DNP C5, C7 1000 pF X7R 1206 500V Ceramic X7R 603 5% 100V Ceramic C8 470 nF X7R 603 25V Ceramic ...
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R11 249Ω 1% R12 3.3 MΩ 1% R13 100Ω 1% R14 150Ω 1% R40 0Ω 5% R16 R17 100kΩ 1% 1/4W 0Ω 1/4W R18, R34, R35 4.7Ω 1% R19 10Ω 1% 1/4W R20 1.8Ω 5% 1/3W R21 ...
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PCB Layout www.national.com Top Layer 6 30103511 ...
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... Warning: The LM3445 evaluation boards have no isolation or any type of protection from shock. Caution must be taken when handling evaluation board. Avoid touching evaluation board, and removing any cables while evaluation board is operating. Isolating the evaluation board rather than the oscilloscope is highly recommended. ...
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... Finally, R27 can be selected using the current, Zener voltage, and transistor parameters: 30103512 3. Average LED Current The LM3445 constant off-time control loop regulates the peak inductor and therefore, peak LED current. The average LED current is related to the peak inductor current by the following relationship: ...
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... Holding Current This LM3445 High Voltage demo board includes five circuit blocks (shown below) that work together to draw additional current from the line at key points in the dimming cycle and ensure a minimum level of current is drawn from the triac dimmer at all times. A description of their operation is outlined below ...
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Output Variation without Component Adjustment If the variation of converter operating parameters is not a concern, the number of LEDs can be adjusted without changes to the evalulation board component values. The ef- fects of changing the LED string ...
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Notes 11 www.national.com ...
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