Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 7
Copyright © 2000
Rev. 1.2c, 2005-05-18
WWW.Microsemi .COM
LX8816
Dual Channel 1A Low Dropout Re
ulator
TM
®
APPLICATION INFORMATION
Layout Consideration
The layout must be done with low impedance paths for V
IN
, V
1,
V
2
and
Ground by using sufficiently wide traces to avoid voltage drops and
noise pick up. The output capacitors must be placed as close as
possible to the voltage regulator output pins. To allow the same
voltage reference for all circuits, use a star configuration from the
output capacitors to the different loads. The input capacitor should be
connected between V
IN
and ground with short leads. Although it may
not be immediately obvious, best load regulation for the adjustable
output is obtained when the top of the resistor divider, (R1), is
connected as close as possible to the case of the regulator, not to the
load.
Heatsink Consideration
The PCB copper can be used as a heatsink for the surface mounted
S-Pak. Using the minimum size as shown in the recommended pad
layout limits the usable power to about 1W for ambient temperature of
50°C. Since most ap
lications require greater than 2W there is the
need to provide additional heat sinking. This can be accomplished by
using additional copper area both on the PCB surface as shown in the
ossible heat sink layout below, or to an embedded ground plane.
Since the die pad (copper tab) is in electrical contact with ground, the
designer can use thermal vias on the surface of the PCB taking
advantage of the heat-spreading (Cu) layer of an internal ground plane.
HEAT SINK LAYOUT
Board Level
Ground
Plane
Component
Trace
B
A
Component
Component Trace
Ground Plane
Inner Power Plane
Backside Trace
VIAS
B
A
Figure 3 - Heatsink
RECOMMENDED MINIMUM PCB FOOTPRINT
11.56mm
9.98mm
8.84mm
3.28mm
.86mm
1.83mm
4.39mm
5.36mm
7.92mm
9.75mm
8.89mm
0mm
1.37mm
A
A
P
P
P
P
L
L
I
I
C
C
A
A
T
T
I
I
O
O
N
N
