ltc1778-1 Linear Technology Corporation, ltc1778-1 Datasheet - Page 19

• Manufacturer Part Number: ltc1778-1
• Description: Wide Operating Range, No Rsense Step-down Controller
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
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 10.
• Segregate the signal and power grounds. All small
• Place M2 as close to the controller as possible, keeping
signal components should return to the SGND pin at
one point which is then tied to the PGND pin close to the
source of M2.
the PGND, BG and SW traces short.
BOLD LINES INDICATE HIGH CURRENT PATHS
R1
R2
C
C
SS
C1
U
R
C
U
C
C2
R
1
2
3
4
5
6
7
8
ON
RUN/SS
PGOOD
V
FCB
I
SGND
I
V
TH
ON
W
RNG
FB
LTC1778
EXTV
BOOST
INTV
PGND
Figure 10. LTC1778 Layout Diagram
SW
V
BG
TG
CC
CC
IN
U
16
15
14
13
12
11
10
9
C
VCC
C
D
B
B
C
F
• Connect the input capacitor(s) C
• Keep the high dV/dT SW, BOOST and TG nodes away
• Connect the INTV
• Connect the top driver boost capacitor C
• Connect the V
R
MOSFETs. This capacitor carries the MOSFET AC
current.
from sensitive small-signal nodes.
to the INTV
BOOST and SW pins.
the V
F
IN
M2
and PGND pins.
C
OUT
CC
D1
IN
M1
and PGND pins.
L
pin decoupling capacitor C
LTC1778/LTC1778-1
CC
C
decoupling capacitor C
IN
1778 F10
IN
+
–
–
+
close to the power
V
V
IN
OUT
B
closely to the
F
VCC
closely to
19
closely
1778fb