ltc3770 Linear Technology Corporation, ltc3770 Datasheet - Page 21

• Manufacturer Part Number: ltc3770
• Description: Fast No Rsense Step-down Synchronous Controller With Margining, Tracking And Pll
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
To set a ±25% margining, select the resistors R3, R4 such
that
or
Choose R3 to be 10k, R4 to be 82k for this application.
PC Board Layout Checklist
When laying out a PC board follow one of two suggested
approaches. The simple PC board layout requires a dedi-
cated 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
39k
11k
R5
R6
V
R4 ≈ 8R3
1 18
REFIN
.
500pF
R
R1
30.1k
CC1
4
•
47k
51k
20k
R7
R8
R
R
= 0.6 ±25% • 0.6
C
3
100pF
=
CC2
95.3k
25
R2
% • .
U
100k
R
10k
0 6
R3
R
75k
PG
INTV
ON
5V
U
82k
CC
RUN
R4
10
11
12
13
14
1
2
3
4
5
6
7
8
9
C
0.1µF
SS
W
RUN
V
PGOOD
V
V
I
SGND
MARGIN1
MARGIN0
I
V
V
MPGM
TRACK/SS
TH
ON
ON
RNG
FB
REFIN
REFOUT
Figure 12. Design Example: 2.5V/10A at 450kHz
LTC3770EG
PLLFLTR
INTV
BOOST
PLLIN
PGND
U
Z
FCB
SW
V
VIN
TG
BG
Z0
Z1
Z2
CC
IN
28
27
26
25
24
23
22
21
20
19
18
17
16
15
0.1µF
CV
IN
• Place C
• Use an immediate via to connect the components to
• Use compact plane for switch node (SW) to improve
• Use planes for V
• Flood all unused areas on all layers with copper. Flood-
it should be as close as possible to the layer with power
MOSFETs.
compact area. It may help to have some components on
the bottom side of the board.
ground plane including SGND and PGND of LTC3770.
Use several bigger vias for power components.
cooling of the MOSFETs and to keep EMI down.
filtering and to keep power losses low.
ing with copper will reduce the temperature rise of
power component. You can connect the copper areas to
any DC net (V
your system).
L1: SUMIDA CEP125-1R8MC-H
C
C
OUT
IN
: UNITED CHEMICON THCR60E1H106ZT
: CORNELL DUBILIER ESRE181E04B
+
+
IN
, C
CB
0.22µF
DB
CMDSH-3
CV
4.7µF
OUT
CC
IN
, MOSFETs, D1 and inductor all in one
, V
IN
M1
Si4884
B340A
M2
Si4874
OUT
and V
D1
1.8µH
L1
, GND or to any other DC rail in
OUT
to maintain good voltage
C
23µF
x5R
x2
OUT3
+
LTC3770
C
180µF
4V
x2
V
2.5V
10A
OUT1-2
OUT
3770 F12
21
C
10µF
50V
x3
V
5V TO 28V
IN
IN
3770fb