sc483itstrt Semtech Corporation, sc483itstrt Datasheet - Page 16

• Manufacturer Part Number: sc483itstrt
• Description: Sc483 Dual Synchronous Buck Pseudo-fixed-frequency Power-supply Controller
• Manufacturer: Semtech Corporation

Layout Guidelines
One (or more) ground planes is/are recommended to minimize the effect of switching noise and copper losses, and
maximize heat dissipation. The IC ground references, VSSA1 and VSSA2, should be kept separate from power
ground. All components that are referenced to them should connect to them locally at the chip. VSSA1 and VSSA2
should connect to power ground at their respective output capacitors only.
Feedback traces must be kept far away from noise sources such as switching nodes, inductors and gate drives.
Route feedback traces with their respective VSSAs as a differential pair from the output capacitor back to the chip.
Run them in a “quiet layer” if possible.
Chip decoupling capacitors (VDDP, VCCA) should be located next to the pins and connected directly to them on the
same side.
Power sections should connect directly to the ground plane(s) using multiple vias as required for current handling
(including the chip power ground connections). Power components should be placed to minimize loops and reduce
losses. Make all the connections on one side of the PCB using wide copper filled areas if possible. Do not use
“minimum” land patterns for power components. Minimize trace lengths between the gate drivers and the gates of
the MOSFETs to reduce parasitic impedances (and MOSFET switching losses), the low-side MOSFET is most critical.
Maintain a length to width ratio of <20:1 for gate drive signals. Use multiple vias as required by current handling
requirement (and to reduce parasitics) if routed on more than one layer
Current sense connections must always be made using Kelvin connections to ensure an accurate signal.
We will examine the SC483 OUT2 reference design used in the Design Procedure section while explaining the layout
guidelines in more detail, using the same generic components for OUT1.
POWER MANAGEMENT
2005 Semtech Corp.
PGOOD
PGOOD
VBAT
VBAT
R1
1M
0402
C4
1nF
0402
R7
1M
0402
C18
1nF
0402
C7
56p
0402
C15
56p
0402
VOUT
VOUT1
VOUT
VOUT2
R4
20k0
0402
R3
20k0
0402
R9
20k0
0402
R13
20k0
0402
Figure 8: Reference Design and Layout Example
R2
10R
0402
R8
10R
0402
5VSUS
5VSUS
C9
1uF
0603
C19
1uF
0603
VSSA1
VSSA2
22
23
24
25
26
27
28
10
11
12
13
14
8
9
U1
EN/PSV1
TON1
VOUT1
VCCA1
FB1
PGD1
VSSA1
EN/PSV2
TON2
VOUT2
VCCA2
FB2
PGD2
VSSA2
N OTES
(1) R 6 and R 12 aid in k eeping VSSA1 and VSSA2 s eparate f rom PGN D ex c ept where des ired in lay out.
SC483
PGND1
PGND2
VDDP1
VDDP2
BST1
ILIM1
BST2
ILIM2
DH1
DH2
DL1
DL2
LX1
LX2
7
6
5
4
3
2
1
21
20
19
18
17
16
15
16
5VSUS
5VSUS
C10
1uF
0603
C20
1uF
0603
R5 7k87
0402
R10 7k87
0402
D1
SOD323
D2
SOD323
C5 0.1uF
0603
C11 0.1uF
0603
IRF7811AV
FDS6676S
IRF7811AV
FDS6676S
Q2
Q1
Q3
Q4
VBAT
VBAT
C6
2n2/50V
0402
C12
2n2/50V
0402
L1
L2
VSSA1
VSSA2
2u2
2u2
R6 0R (1)
R12 0R (1)
C1
0u1/25V
0603
0402
C13
0u1/25V
0603
0402
C2
10u/25V
1210
C14
10u/25V
1210
+
+
C8
220u/25m
7343
C16
220u/25m
7343
+
+
C3
220u/25m
7343
C17
220u/25m
7343
www.semtech.com
VOUT1
VOUT2
SC483