Datasheet
20
LTC3778
3778f
APPLICATIO S I FOR ATIO
WUUU
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 C
IN
, C
OUT
, 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).
Figure 9. LTC3778 Layout Diagram
20
19
18
17
16
15
14
13
12
11
C
C2
BOLD LINES INDICATE HIGH CURRENT PATHS
C
C1
C
SS
C
FB
C
ION
R
ON
R
C
R
F
3778 F10
1
2
3
4
5
6
7
8
9
10
RUN/SS
V
ON
PGOOD
V
RNG
I
TH
FCB
SGND
I
ON
V
FB
EXTV
CC
BOOST
TG
SW
SENSE+
SENSE–
PGND
BG
DRV
CC
INTV
CC
V
IN
C
B
M2
M1
D1
D
B
C
F
C
VCC
C
OUT
C
IN
V
IN
V
OUT
+
–
+
–
LTC3778
L
R1
R2
+
•
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 V
IN
and V
OUT
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 (V
IN
, V
OUT
, 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.