Microchip Technology ADM00427 Scheda Tecnica
© 2011 Microchip Technology Inc.
DS22284A-page 21
MCP16323
5.0.9
PCB LAYOUT INFORMATION
Good printed circuit board layout techniques are
important to any switching circuitry, and switching
power supplies are no different. When wiring the
switching high-current paths, short and wide traces
should be used. Therefore, it is important that the input
and output capacitors be placed as close as possible to
the MCP16323 to minimize the loop area.
The feedback resistors and feedback signal should be
routed away from the switching node and the switching
current loop. When possible, ground planes and traces
should be used to help shield the feedback signal and
minimize noise and magnetic interference.
A good MCP16323 layout starts with C
important to any switching circuitry, and switching
power supplies are no different. When wiring the
switching high-current paths, short and wide traces
should be used. Therefore, it is important that the input
and output capacitors be placed as close as possible to
the MCP16323 to minimize the loop area.
The feedback resistors and feedback signal should be
routed away from the switching node and the switching
current loop. When possible, ground planes and traces
should be used to help shield the feedback signal and
minimize noise and magnetic interference.
A good MCP16323 layout starts with C
IN
placement.
C
IN
supplies current to the input of the circuit when the
switch is turned on. In addition to supplying high-
frequency switch current, C
IN
also provides a stable
voltage source for the internal MCP16323 circuitry.
Unstable PWM operation can result if there are
excessive transients or ringing on the V
Unstable PWM operation can result if there are
excessive transients or ringing on the V
IN
pin of the
MCP16323 device. In
, C
IN
is placed close to
the V
IN
pins. A ground plane on the bottom of the board
provides a low resistive and low inductive path for the
return current. The next priority in placement is the
freewheeling current loop formed by C
return current. The next priority in placement is the
freewheeling current loop formed by C
OUT
and L while
strategically placing the C
OUT
return close to C
IN
return. Next, C
BOOST
should be placed between the
boost pin and the switch node pin. This leaves space
close to the MCP16323 V
close to the MCP16323 V
FB
pin to place R
TOP
and
R
BOT
. R
TOP
and R
BOT
are routed away from the switch
node so noise is not coupled into the high-impedance
V
V
FB
input.
FIGURE 5-1:
Recommended Layout.
V
OUT
GND
GND
C
IN
C
OUT
C
OUT
R
BOT
R
TOP
10
Ω
R
PG
Bottom layer is a 2 oz
copper ground plane
Trace on
bottom layer
C
IN
V
IN
L
MCP16323
Top layer is made
with 2 oz copper
Board Dimensions
are 2.5" by 2.5"
The 2 middle
layers are made
with 1 oz copper
and connected to
V
IN
and GND
C
BOOST