CL6807 查看數據表（PDF） - Unspecified

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CL6807

30V 1A LED driver with internal switch

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CHIPLINK

SEMICONDUCTOR

CL6807

Freewheeling Diode Selection

The forward voltage of the freewheeling diode should be as low as possible for better efficiency.

A Schottky diode is a good choice as long as the breakdown voltage is high enough to withstand

the maximum operating voltage. The forward current rating of the diode must be at least equal to

the maximum LED current.

LED Current Ripple

The LED current ripple is equal to the inductor current ripple. In cases when a lower LED current

ripple is needed, a capacitor can be placed across the LED terminals.

PCB Layout Guidelines

Careful PCB layout is critical to achieve low switching losses and stable operation. Use a

multilayer board whenever possible for better noise immunity. Minimize ground noise by connecting

high-current ground returns, the input bypass-capacitor ground lead, and the output-filter ground

lead to a single point (star ground configuration). In normal operation, there are two power loops.

One is formed when the internal MOSFET is on and the high current flows through IN—RSENSE—

LEDs—Inductor—MOSFET—GND. The other loop is formed when the internal MOSFET is off

when the high current circulates through RSENSE—LEDs—Inductor—freewheeling diode. To

minimize noise interaction, each loop area should be as small as possible. Place RSENSE as close as

possible to the input filter and VIN. For better noise immunity, a Kelvin connection is strongly

recommended between ISNS and RSENSE. Connect the exposed paddle to a large-area ground

plane for improved power dissipation.

2008-09-09

6

http://www.chiplink-semi.com

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