SC411 Semtech Corporation, SC411 Datasheet - Page 19

• Manufacturer Part Number: SC411
• Description: Synchronous Buck Pseudo-Fixed Frequency Power Supply Controller
• Manufacturer: Semtech Corporation

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As shown below, VOUT should be routed away from noisy traces (such as BST, DH, DL and LX) and in a quiet layer (if
possible) to the output capacitor(s).
Next, the schematic in Figure 8 below shows the power section. The highest di/dts occur in the input loop (highlight-
ed in red) and thus this loop should be kept as small as possible.
The input capacitors should be placed with the highest frequency capacitors closest to the loop to reduce EMI. Use
large copper pours to minimize losses and parasitics. See Figure 9 for an example.
© 2007 Semtech Corp.
POWER MANAGEMENT
I R F 7 8 1 1 A V
F D S 6 6 7 6 S
Q 1
Q 2
V B A T
C5
56p
0402
VOUT
R3
20k0
0402
R5
14k3
0402
Figure 8: Power Section and Input Loop
Figure 7: VOUT Sense Trace Routing
C 2
2 n 2 / 5 0 V
0 4 0 2
1
2
3
4
L 1
VOUT
VCCA
FB
PGD
U1
2 u 2
SC411
C 3
0 u 1 / 2 5 V
0 6 0 3
19
+
C 6
2 2 0 u / 2 5 m
7 3 4 3
VDDP
ILIM
DH
LX
C 4
1 0 u / 2 5 V
1 2 1 0
12
11
10
9
+
7 3 4 3
C 7
2 2 0 u / 2 5 m
+
C6
220u/25m
7343
+
C7
220u/25m
7343
V O U T
VOUT
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SC411