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LM3444 Datasheet(PDF) 7 Page - Texas Instruments |
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LM3444 Datasheet(HTML) 7 Page - Texas Instruments |
7 / 27 page ICOLL V+ VAC + + 1 2 3 4 5 6 7 8 9 1 0 - VLED G N D VC C FILT ER NC NC ISN S GAT E NC CO FF N C LM344 4 VLED- D 3 C 7 C 9 C 1 0 D 4 D 8 D 9 R 2 D 1 Q 1 C 5 C 1 2 D2 D1 0 Q2 L 2 Q3 R 3 R 4 C 1 1 C 4 U1 VBUCK BR1 LM3444 www.ti.com SNVS682B – NOVEMBER 2010 – REVISED NOVEMBER 2011 APPLICATION INFORMATION FUNCTIONAL DESCRIPTION The LM3444 contains all the necessary circuitry to build a line-powered (mains powered) constant current LED driver. Theory of Operation Refer to Figure 11 below which shows the LM3444 along with basic external circuitry. Figure 11. LM3444 Schematic VALLEY-FILL CIRCUIT VBUCK supplies the power which drives the LED string. Diode D3 allows VBUCK to remain high while V+ cycles on and off. VBUCK has a relatively small hold capacitor C10 which reduces the voltage ripple when the valley fill capacitors are being charged. However, the network of diodes and capacitors shown between D3 and C10 make up a "valley-fill" circuit. The valley-fill circuit can be configured with two or three stages. The most common configuration is two stages. Figure 12 illustrates a two and three stage valley-fill circuit. Copyright © 2010–2011, Texas Instruments Incorporated Submit Documentation Feedback 7 Product Folder Links: LM3444 |
Similar Part No. - LM3444_14 |
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Similar Description - LM3444_14 |
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