LTC3855 LINER [Linear Technology], LTC3855 Datasheet - Page 42

• Manufacturer Part Number: LTC3855
• Description: Dual, Fast, Accurate Step-Down DC/DC Controller
• Manufacturer: LINER [Linear Technology]

LTC3838
APPLICATIONS INFORMATION
• Keep the switch nodes (SW1,2), top gates (TG1,2) and
42
boost nodes (BOOST1,2) away from noise-sensitive
small-signal nodes, especially from the opposite
channel’s voltage and current sensing feedback pins.
These nodes have very large and fast moving signals
and therefore should be kept on the “output side” of
R
R
FB2(2)
FB1(2)
R
R
R
R
ITH2(2)
ITH1(2)
SGND TRACE
ITH1(1)
ITH2(1)
LOCALIZED
BOLD LINES INDICATE HIGH SWITCHING CURRENT. KEEP LINES TO A MINIMUM LENGTH.
C
R
ITH2(2)
FB2(1)
C
ITH2(1)
C
ITH1(2)
C
ITH1(1)
C
R
SS1
C
R
FB1(1)
SS2
T
DTR2
SENSE2
SENSE2
V
TRACK/SS2
ITH2
V
PHASMD
MODE/PLLIN
CLKOUT
SGND
RT
V
ITH1
TRACK/SS1
V
V
SENSE1
SENSE1
FB2
RNG2
RNG1
OUTSENSE1
OUTSENSE1
–
+
+
–
+
–
Figure 14. Recommended PCB Layout Diagram
PGOOD2
PGOOD1
BOOST2
BOOST1
DRV
DRV
EXTV
INTV
PGND
RUN2
RUN1
DTR1
SW2
SW1
BG2
TG2
BG1
TG1
CC2
CC1
V
CC
CC
IN
C
B2
R
C
C
C
INTVCC
INTVCC
DRVCC
B1
D
D
B1
B2
the LTC3838 (power-related pins are toward the right
hand side of the IC), and occupy minimum PC trace
area. Use compact switch node (SW) planes to improve
cooling of the MOSFETs and to keep EMI down. If DCR
sensing is used, place the top filter resistor (R1 only in
Figure 5) close to the switch node.
C
VIN
R
VIN
MT2
V
MT1
IN
CERAMIC
+
CERAMIC
C
L2
IN
L1
MB2
MB1
R
R
SENSE2
SENSE1
PGND
C
C
OUT2
OUT1
V
V
OUT2
OUT1
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