LTC3608 LINER [Linear Technology], LTC3608 Datasheet - Page 18

• Manufacturer Part Number: LTC3608
• Description: 18V, 8A Monolithic Synchronous Step-Down DC/DC Converter
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
LTC3608
• Use a compact plane for the switch node (SW) to improve
• Use planes for V
• Flood all unused areas on all layers with copper. Flood-
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 7.
18
2.5V AT
V
GND
cooling of the MOSFETs and to keep EMI down.
fi ltering and to keep power losses low.
ing with copper reduces the temperature rise of power
components. Connect these copper areas to any DC
net (V
system).
OUT
8A
(OPTIONAL)
5V TO 18V
C
C
L1: CDEP85NP-R80MC-50
C5: MURATA GRM31CR60J226KE19
KEEP POWER GROUND AND SIGNAL GROUND SEPARATE.
CONNECT AT ONE POINT.
22μF
10μF
IN
OUT
6.3V
35V
C
: TAIYO YUDEN GMK325BJ106MM-B
C5
= PGND
= SGND
3×
IN
IN
: TDKC2012X5ROJ226M
V
IN
, V
(OPTIONAL)
OUT
C
100μF
OUT1
10μF
35V
, GND or to any other DC rail in your
×2
C6
IN
+
+
and V
GND
0.8μH
L1
V
IN
OUT
PGND
41
42
43
44
45
46
47
48
49
50
51
52
Figure 6. Design Example: 5V to 18V Input to 2.5V/8A at 550kHz
to maintain good voltage
SW
SW
SW
SW
SW
SW
SW
PV
PV
PV
PV
PV
IN
IN
IN
IN
IN
40 39 38 37 36 35 34 33 32 31 30 29 28 27
1
2
3
INTV
4
CC
5
4.7μF
C
6.3V
VCC
CMDSH-3
6
D
LTC3608
B
7
8
SW
SW
INTV
SW
9 10 11 12 13 14
CC
C
0.22μF
B1
• Segregate the signal and power grounds. All small
• 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
signal components should return to the SGND pin at
one point, which is then tied to the PGND pin.
capacitor carries the MOSFET AC current.
from sensitive small-signal nodes.
to the INTV
the BOOST and SW pins.
the V
C
0.1μF
C
0.47μF
25V
SS
F
IN
PGOOD
SGND
SGND
SGND
V
and PGND pins.
FCB
RNG
V
I
I
NC
NC
NC
ON
TH
FB
R
1Ω
F1
26
25
24
23
22
21
20
19
18
17
16
15
CC
V
IN
and PGND pins.
IN
(OPTIONAL)
pin decoupling capacitor C
R
510k
CC
SS1
SGND
R1
9.5k
1%
decoupling capacitor C
R3
0Ω
C4
0.01μF
V
IN
EXTV
(OPTIONAL)
R
100k
PG1
C1
C
0.01μF
CC
ON
INTV
CC
IN
(OPTIONAL)
0.1μF
187k
R
1%
close to the IC. This
(OPTIONAL)
ON
11.3k
R5
C3
R
R2
30.1k
1%
0Ω
VON
B
1500pF
F
100pF
VCC
C
C
C1
closely to
closely to
C2
(OPTIONAL)
3608 F06
C2
closely
V
V
SGND
V
3608fa
OUT
IN
OUT