ltc3728legn-trpbf Linear Technology Corporation, ltc3728legn-trpbf Datasheet - Page 29

• Manufacturer Part Number: ltc3728legn-trpbf
• Description: Dual, 550khz, 2-phase Synchronous Step-down Switching Regulator
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC3728. These items are also illustrated graphically in
the layout diagram of Figure 10. The Figure 11 illustrates
the current waveforms present in the various branches
of the 2-phase synchronous regulators operating in the
continuous mode. Check the following in your layout:
1. Are the top N-channel MOSFETs M1 and M3 located
within 1cm of each other with a common drain connection
at C
the two channels as it can cause a large resonant loop.
IN
? Do not attempt to split the input decoupling for
R1
R3
R2
R4
INTV
3.3V
CC
f
IN
10
11
12
13
14
1
2
3
4
5
6
7
8
9
Figure 10. LTC3728 Recommended Printed Circuit Layout Diagram
RUN/SS1
SENSE1
SENSE1
V
PLLFLTR
PLLIN
FCB
I
SGND
3.3V
I
V
SENSE2
SENSE2
TH1
TH2
OSENSE1
OSENSE2
OUT
+
–
LTC3728
–
+
RUN/SS2
BOOST1
BOOST2
EXTV
PGOOD
INTV
PGND
SW1
SW2
BG1
BG2
TG1
TG2
V
CC
CC
IN
28
27
26
25
24
23
22
21
20
19
18
17
16
15
2. Are the signal and power grounds kept separate? The
combined LTC3728 signal ground pin and the ground return
of C
The path formed by the top N-channel MOSFET, Schottky
diode and the C
PC trace lengths. The output capacitor (–) terminals should
be connected as close as possible to the (–) terminals
of the input capacitor by placing the capacitors next to
each other and away from the Schottky loop described
above.
3. Do the LTC3728 V
to the (+) terminals of C
be connected between the (+) terminal of C
R
PGOOD
PU
INTVCC
C
C
C
B1
B2
INTVCC
V
(<7V)
PULL-UP
must return to the combined C
C
VIN
V
R
IN
IN
M1
IN
M3
capacitor should have short leads and
OSENSE
M2
M4
OUT
L1
C
L2
IN
pins resistive dividers connect
? The resistive divider must
R
R
SENSE
SENSE
C
C
D1
OUT1
OUT2
D2
LTC3728
OUT
3728 F10
OUT
(–) terminals.
V
GND
V
OUT1
OUT2
and signal
29
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