LTC3778 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC3778' PDF : 24 Pages View PDF
LTC3778
APPLICATIO S I FOR ATIO
PC Board Layout Checklist
When laying out a PC board follow one of the two sug-
gested approaches. The simple PC board layout requires
a dedicated ground plane layer. Also, for higher currents,
it is recommended to use a multilayer board to help with
heat sinking power components.
• The ground plane layer should not have any traces and
it should be as close as possible to the layer with power
MOSFETs.
• Place CIN, COUT, MOSFETs, D1 and inductor all in one
compact area. It may help to have some components on
the bottom side of the board.
• Place LTC3778 chip with pins 11 to 20 facing the power
components. Keep the components connected to pins
1 to 9 close to LTC3778 (noise sensitive components).
• Use an immediate via to connect the components to
ground plane including SGND and PGND of LTC3778.
Use several bigger vias for power components.
• Use compact plane for switch node (SW) to improve
cooling of the MOSFETs and to keep EMI down.
• Use planes for VIN and VOUT to maintain good voltage
filtering and to keep power losses low.
• Flood all unused areas on all layers with copper. Flood-
ing with copper will reduce the temperature rise of
power component. You can connect the copper areas to
any DC net (VIN, VOUT, GND or to any other DC rail in
your system).
When laying out a printed circuit board, without a ground
plane, use the following checklist to ensure proper opera-
tion of the controller. These items are also illustrated in
Figure 9.
20
CSS
CC1 RC
CC2
CION
CFB
R1
LTC3778
1 RUN/SS
20
BOOST
2
VON
3
PGOOD
19
TG
18
SW
4
VRNG
5
ITH
6
FCB
17
SENSE+
16
SENSE–
15
PGND
7
SGND
14
BG
8
ION
13
DRVCC
9
VFB
12
INTVCC
10
EXTVCC
11
VIN
CB
DB
CVCC
CF
RF
R2
RON
BOLD LINES INDICATE HIGH CURRENT PATHS
L
M1
D1
CIN
M2
COUT
3778 F10
+
VIN
–
–
VOUT
+
Figure 9. LTC3778 Layout Diagram
3778f
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