AL8808EV2
Issue 1 – January 2013 www.diodes.com
© Diodes Incorporated 2013
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AL8808EV2 EVALUATION BOARD REFERENCE DESIGN
The AL8808EV2 is configured to the reference design shown in Figure 3. For other reference designs
or further applications information, please refer to the AL8808 datasheet.
The operating voltage is a nominal 12V AC or DC. The nominal current is set at 680mA with a 0R15
sense resistor R1. The circuit operates in continuous mode at approximately 300kHz, (with DC
voltage), with a 33uH inductor and one LED.
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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.
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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 C2 is needed.
C1 is not fitted.
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C3 provides local decoupling for the AL8808 device U1. It is important that this is as close as
possible to U1, as shown in the layout. C4 decouples the LED connections to minimise EMI
and to smooth the current.
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L1 smooth’s the switching at LX into a DC current for the LED string. D1 operates as the
freewheeling diode, preventing large voltage spikes at LX.
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L2 is not fitted, and the pads are shorted with a link on this evaluation board. Its purpose is to
reduce EMI. Both 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.
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R1 sets the LED current. The 0R15 resistor shown gives a LED current of 680mA.
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Optional extra parts are marked by an asterisk and are NOT fitted on the PCB.
Figure 3. Schematic diagram of full PCB including not fitted components options on PCB
