Diodes AL8805 Manuel d'utilisateur télécharger pdf (Page 13)

AL8805

Document number: DS35030 Rev. 4 - 2

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www.diodes.com

July 2012

L8805

Application Information (cont.)

Thermal and Layout Considerations

Figure 35 gives details about the PCB layout suggestions:

1. the capacitor C1 has to be placed as close as possible to V

2. The sense resistor R1 has to be placed as close as possible to V

and SET

3. The D1 anode, the SW pin and the inductor have to be placed as close as possible to avoid ringing.

Figure 35 Recommended PCB Layout

Application Example

Typical application example for the AL8805 is the MR16 lamp. They typically operate from 12V

or 12V

, using conventional electromagnetic

transformers or electronic transformers.

As a replacement in some halogen lamp applications LEDs offer a more energy efficient solution – providing no radiated heat and no Ultra Violet

light.

This application example is intended to fit into the base connector space of an MR16 style LED lamp. The design has been optimized for part

count and thermal performance for a single 3W LED in the Lens section.

Figure 36 MR16 Schematic

An inductor choice of 33µH with saturation current higher than 1.1A, will limit the frequency variation between 230kHz and 350kHz over the

whole input voltage variation (8V to 18V), and therefore represent the best choice for an MR16 solution also taking into account the size

constraint of the lamp.

The AL8805 guarantee high level of performance both with 12V

and 12V

power supply.

The efficiency is generally higher than 81% and current regulation is better than 0.1mA/V in for a DC input voltage in the range from 8V to 18V.

In table 1 can be found the bill of material of the MR16 application example.

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Diodes AL8805 Manuel d'utilisateur Page 13