データシートサーチシステム |
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LM3464A データシート(PDF) 10 Page - National Semiconductor (TI) |
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LM3464A データシート(HTML) 10 Page - National Semiconductor (TI) |
10 / 22 page 30115003 FIGURE 1. Typical Application Circuit with Fly-Back AC/DC Converter Overview The LM3464/64A is a four channel linear current regulator designed for LED lighting systems with wide input voltage range, high speed PWM and thermal foldback dimming con- trol interface. The LM3464/64A incorporates a Dynamic Headroom Control (DHC) technology which maximizes over- all efficiency of the lighting system by adjusting the output voltage of the primary power source dynamically. Linear cur- rent regulation secures high accuracy output current, LED and system reliability. High speed PWM dimming provides the flexibility of brightness control while maintaining constant col- or temperature of the light. The thermal foldback feature enables the LM3464/64A to manage the temperature of the LED heat sink or system chassis with a simple NTC/PTC temperature sensor. The thermal foldback input can also be used as an analog dimming control input to adapt to other sensors easily, such as ambient light sensor. Dynamic Headroom Control (DHC) Operation Principles of DHC Dynamic Headroom Control is a technology that aims at max- imizing the overall system efficiency by altering the supply voltage to the LED(s) dynamically in respect to the charac- teristics of the LED(s). In the LM3464/64A, DHC is facilitated by connecting a resistor in between the OutP pin of the LM3464/64A and the voltage feedback node of the primary power supply (AC/DC) as shown in Figure 2. 30115004 FIGURE 2. Circuitry of the DHC Mechanism For example, in steady state, when all the output channels are in regulation and the forward voltage of any LED string decreases due to temperature raise, the drain voltage of the corresponding channel (DRx) increases to exceed the default 0.9V typical headroom voltage in order to maintain constant output current. As the drain voltage increases, the voltage of CDHC increases and the current sink into the OutP pin de- creases. This will finally result in decrease of rail voltage (V RAIL) until the corresponding DRx voltage returns to mini- mum level. www.national.com 10 |
同様の部品番号 - LM3464A |
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同様の説明 - LM3464A |
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