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| LTC3609 Datasheet, PDF (18/24 Pages) Linear Technology – 32V, 6A Monolithic Synchronous Step-Down DC/DC Converter | |||
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LTC3609
APPLICATIONS INFORMATION
INTVCC
CVCC
4.7μF
6.3V
VIN
CF
RF1
0.1μF 1Ω
50V
SW
GND
40 39 38 37 36 35 34 33 32 31 30 29 28 27
VOUT
2.5V AT
6A
COUT1 +
100μF
x2
GND
L1
1.2μH
VIN
VIN
5V TO 32V
CIN
4.7μF
50V
x2
41 SW
42 SW
43 SW
44
SW
45 SW
46 SW
47 SW
48 PVIN
49 PVIN
50 PVIN
51
PVIN
52
PVIN
LTC3609
SGND 26
NC 25
NC 24
23
VFB
ION 22
NC 21
SGND 20
19
FCB
ITH 18
VRNG 17
16
PGOOD
SGND 15
EXTVCC
C4
0.01μF
R1
9.53k
1%
R2
30.1k
1%
VOUT
RON
187k
1%
VIN
R5
CC1
1000pF
15.8k
INTVCC
JP1
RPG1
100k
CC2
100pF
1 2 3 4 5 6 7 8 9 10 11 12 13 14
CIN: MURATA GRM32ER71H475K
COUT: MURATA GRM435R60J107M
LI: CDEP851R2MC-50
KEEP POWER GROUND AND SIGNAL
GROUND SEPARATE. CONNECT AT
ONE POINT.
SW
2Ω
INTVCC
DB
CMDSH-3
CB1
0.22μF
SW
CSS
0.1μF
CVON
0.1μF
PGOOD
SGND
VOUT
Figure 6. Design Example: 5V to 32V Input to 2.5V/6A at 550kHz
INTVCC
3609 F06
⢠Use a compact plane for the switch node (SW) to improve
cooling of the MOSFETs and to keep EMI down.
⢠Use planes for VIN and VOUT to maintain good voltage
ï¬ltering and to keep power losses low.
⢠Flood all unused areas on all layers with copper. Flood-
ing with copper reduces the temperature rise of power
components. Connect these copper areas to any DC
net (VIN, VOUT, GND or to any other DC rail in your
system).
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
⢠Segregate the signal and power grounds. All small
signal components should return to the SGND pin at
one point, which is then tied to the PGND pin.
⢠Connect the input capacitor(s) CIN close to the IC. This
capacitor carries the MOSFET AC current.
⢠Keep the high dV/dT SW, BOOST and TG nodes away
from sensitive small-signal nodes.
⢠Connect the INTVCC decoupling capacitor CVCC closely
to the INTVCC and PGND pins.
⢠Connect the top driver boost capacitor CB closely to
the BOOST and SW pins.
⢠Connect the VIN pin decoupling capacitor CF closely to
the VIN and PGND pins.
3609f
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