Al8807, Application information – Diodes AL8807 User Manual
Page 15
AL8807
Document number: DS35281 Rev. 5 - 2
15 of 20
March 2013
© Diodes Incorporated
AL8807
Application Information
(cont.)
Recommendations for minimising radiated EMI and other transients and thermal considerations are:
1.
The decoupling capacitor (C1) has to be placed as close as possible to the V
IN
pin and D1 Cathode
2.
The freewheeling diode’s (D1) anode, the SW pin and the inductor have to be placed as close as possible to each other to avoid ringing.
3.
The Ground return path from C1 must be a low impedance path with the ground plane as large as possible
4.
The LED current sense resistor (R1) has to be placed as close as possible to the V
IN
and SET pins.
5.
The majority of the conducted heat from the AL8807 is through the GND pin 2. A maximum earth plane with thermal vias into a second earth
plane will minimise self-heating
6.
To reduce emissions via long leads on the supply input and LEDs low RF impedance capacitors (C2 and C5) should be used at the point the
wires are joined to the PCB
A typical application for the AL8807 is an LED MR16 lamp (schematic shown in Figure 38).
Figure 38 MR16 Circuit Schematic
An evaluation board for the AL8807 (named the AL8807EV2) for MR16 is available on request from your local Diodes’ sales representative. This
board follows Diodes’ recommendations for low EMI. Images of the top layer and bottom layers are shown in Figure 39.
Figure 39 Recommended MR16 PCB Layout