LTC3703-5
29
37035fa
APPLICATIO S I FOR ATIO
W
U
U
U
Figure 20. LTC3703-5 Buck Converter Suggested Layout
LTC3703-5
MODE/SYNC
FSET
COMP
FB
I
MAX
INV
RUN/SS
GND
V
IN
BOOST
TG
SW
VCC
DRV
CC
BG
BGRTN
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
C
C1
C
IN
C
C2
C
C3
R
C1
R
C2
R1
R2
R
F
R
MAX
R
SET
C
B
V
IN
M1
M2
L1
D1
V
OUT
C
OUT
D
B
V
CC
C
SS
37035 F18
C
DRVCC
X5R
C
VCC
X5R
+
+
+
–
5. Place the small-signal components away from high
frequency switching nodes (BOOST, SW, TG, and BG). In
the layout shown in Figure 20, all the small signal compo-
nents have been placed on one side of the IC and all of the
power components have been placed on the other. This
also helps keep the signal ground and power ground
isolated.
6. A separate decoupling capacitor for the supply, V
CC
, is
useful with an RC filter between the DRV
CC
supply and V
CC
pin to filter any noise injected by the drivers. Connect this
capacitor close to the IC, between the V
CC
and GND pins
and keep the ground side of the V
CC
capacitor (signal
ground) isolated from the ground side of the DRV
CC
capacitor (power ground).
7. For optimum load regulation and true remote sensing,
the top of the output resistor divider should connect
independently to the top of the output capacitor (Kelvin
connection), staying away from any high dV/dt traces.
Place the divider resistors near the LTC3703-5 in order to
keep the high impedance FB node short.
8. For applications with multiple switching power convert-
ers connected to the same input supply, make sure that the
input filter capacitor for the LTC3703-5 is not shared with
other converters. AC input current from another converter
could cause substantial input voltage ripple, and this could
interfere with the operation of the LTC3703-5. A few
inches of PC trace or wire (L
≅
100nH) between C
IN
of the
LTC3703-5 and the actual source V
IN
should be sufficient
to prevent input noise interference problems.
