LTC3851 LINER [Linear Technology], LTC3851 Datasheet - Page 22

• Manufacturer Part Number: LTC3851
• Description: Synchronous Step-Down Switching Regulator Controller
• Manufacturer: LINER [Linear Technology]

LTC3851
APPLICATIONS INFORMATION
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of
the LTC3851. These items are also illustrated graphically
in the layout diagram of Figure 9. Check the following in
your layout:
1. Are the board signal and power grounds segregated?
22
The LTC3851 GND pin should tie to the ground plane
close to the input capacitor(s). The low current or signal
ground lines should make a single point tie directly to
the GND pin. The synchronous MOSFET source pins
should connect to the input capacitor(s) ground.
47pF
R
C
R
0.1μF
C
FREQ
SS
1000pF
C
C
C
C2
1
2
3
4
5
6
7
8
MODE/PLLIN
FREQ/PLLFLTR
RUN
TK/SS
I
V
SENSE
SENSE
TH
FB
LTC3851
–
+
Figure 9. LTC3851 Layout Diagram
INTV
BOOST
GND
I
SW
V
LIM
BG
TG
CC
IN
16
15
14
13
12
11
10
9
R1
R2
+
+
C
4.7μF
2. Does the V
3. Are the SENSE
OUT
D
B
tors? The resistive divider R1, R2 must be connected
between the (+) plate of C
47pF to 100pF capacitor should be as close as possible
to the LTC3851. Be careful locating the feedback resis-
tors too far away from the LTC3851. The V
not be routed close to any other nodes with high slew
rates.
with minimum PC trace spacing? The fi lter capaci-
tor between SENSE
as possible to the LTC3851. Ensure accurate current
sensing with Kelvin connections as shown in Figure
10. Series resistance can be added to the SENSE lines
to increase noise rejection and to compensate for the
ESL of R
C
B
SENSE
M1
FB
R
L1
SENSE
pin connect directly to the feedback resis-
.
–
M2
D1
and SENSE
+
and SENSE
C
IN
OUT
+
3851 F09
and signal ground. The
leads routed together
–
V
V
OUT
should be as close
+
–
–
+
IN
FB
line should
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