AL8807EV2

Issue 2 – February 2012

www.diodes.com

© Diodes Incorporated 2012

5

AL8807EV2 EVALUATION BOARD

FULL COMPONENT OPTIONS FOR THE PCB LAYOUT

Figure 4: Schematic diagram of full PCB including not fitted Components options on PCB

AL8807EV2 Full Circuit description

P1 and P2 are the power input pads, feeding into the bridge rectifier, comprising of D2, D3, D4 and

D5. C5 offers EMI filtering at the input pads.

C1 and C2 form the bulk reservoir capacitance, used to sustain operation of the device during the low

part of the AC wave. In the case of a system driving a single LED, only one capacitor of 150uF is

needed.

L2 and C6 form a filter circuit to reduce conducted EMI if necessary. In many cases they may not be

required, and where that is so, then L2 pads are shorted out and C6 is not fitted.

C3 provides local decoupling for the AL8807 device U1. It is important that this is as close as possible

to U1, as shown in the layout.

R1 sets the LED current. The 0R15 resistor shown gives a LED current of 680mA.

C4 decouples the LED connections, again to minimise EMI, as well as smoothing the current.

L1 smoothes the switching at LX into a DC current for the LED string. D1 operates as the

freewheeling diode, preventing large voltage spikes at LX.

AL8807EV2 Basic operation at full voltage

1.

Connect P1 and P2 to the power supply

2.

Set the PSU to 12VAC or 12VDC

3.

Turn on the PSU and the LED will illuminate and the current should be approximately 680mA.

Warning: Do not stare at the LED directly.