sc183c Semtech Corporation, sc183c Datasheet - Page 18

• Manufacturer Part Number: sc183c
• Description: 2.5mhz, 2a Synchronous Step-down Regulator
• Manufacturer: Semtech Corporation

© 2009 Semtech Corp.
Applications Information (continued)
PCB Layout Considerations
The layout diagram in Figure 5 shows a recommended
top-layer PCB for the SC83C and supporting components.
Figure 6 shows the bottom layer for this PCB. Fundamental
layout rules must be followed since the layout is critical for
achieving the performance specified in the Electrical
Characteristics table. Poor layout can degrade the perfor-
mance of the DC-DC converter and can contribute to EMI
problems, ground bounce, and resistive voltage losses.
Poor regulation and instability can result.
The following guidelines are recommended when devel-
oping a PCB layout:
.
2.
3.
4.
5.
The input capacitor, C
the PVIN and PGND pins as possible. This capacitor
provides a low impedance loop for the pulsed currents
present at the buck converter’s input. Use short wide
traces to connect as closely to the IC as possible.
This will minimize EMI and input voltage ripple by
localizing the high frequency current pulses.
Keep the LX pin traces as short as possible to minimize
pickup of high frequency switching edges to other
parts of the circuit. C
close as possible between the LX and GND pins, with
a direct return to the GND pin from C
Route the output voltage feedback/sense path away
from inductor and LX node to minimize noise and
magnetic interference.
Use a ground plane referenced to the SC83C PGND
pin. Use several vias to connect to the component
side ground to further reduce noise and interference
on sensitive circuit nodes.
If possible, minimize the resistance from the VOUT
and AGND pins to the load. This will reduce the
voltage drop on the ground plane and improve the
load regulation. And it will also improve the overall
efficiency by reducing the copper losses on the output
and ground planes.
OUT
IN
and L should be connected as
should be placed as close to
OUT
.
8
GND
VIN
Figure 5 — Recommended PCB Layout
Figure 6 — Bottom Layer Detail
VIN
L
CTLx
GND
GND
U1
C
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OUT
SC183C
VOUT
VOUT
GND