LTC3728 Linear Technology, LTC3728 Datasheet - Page 26

• Manufacturer Part Number: LTC3728
• Description: 2-Phase Synchronous Step-Down Switching Regulator
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
LTC3728
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
two channels as it can cause a large resonant loop.
26
IN
? Do not attempt to split the input decoupling for the
R1
R3
R2
R4
U
INTV
3.3V
CC
U
f
IN
10
11
12
13
14
Figure 10. LTC3728 Recommended Printed Circuit Layout Diagram
1
2
3
4
5
6
7
8
9
RUN/SS1
SENSE1
SENSE1
V
PLLFLTR
PLLIN
FCB
I
SGND
3.3V
I
V
SENSE2
SENSE2
TH1
TH2
OSENSE1
OSENSE2
W
OUT
LTC3728
+
–
–
+
RUN/SS2
BOOST1
BOOST2
EXTV
PGOOD
INTV
PGND
SW1
SW2
BG1
BG2
TG1
TG2
V
U
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
terminals. The path formed by the top N-channel MOSFET,
Schottky diode and the C
leads and PC trace lengths. The output capacitor (–)
terminals should be connected as close as possible to the
(–) terminals of the input capacitor by placing the capaci-
tors next to each other and away from the Schottky loop
described above.
3. Do the LTC3728 V
nect to the (+) terminals of C
must be connected between the (+) terminal of C
R
PGOOD
PU
C
C
C
B1
B2
INTVCC
V
(<7V)
PULL-UP
INTVCC
C
VIN
V
R
IN
M1
IN
M3
must return to the combined C
OSENSE
M2
M4
C
L1
L2
IN
IN
capacitor should have short
pins resistive dividers con-
OUT
R
www.DataSheet4U.com
R
SENSE
? The resistive divider
SENSE
C
C
OUT1
OUT2
D1
D2
3728 F10
V
GND
V
OUT1
OUT2
OUT
OUT
3728fb
and
(–)