Datasheet

MCP14628
DS22083A-page 12 © 2008 Microchip Technology Inc.
FIGURE 5-1: Turn On Current Paths.
The charge needed for the turning on of the high-side
power MOSFET comes from the bootstrap capacitor
C
BOOT
. Current flows from C
BOOT
through the internal
HIGHDR circuitry, into the gate of the high-side power
MOSFET, out the source, and back to C
BOOT
. The
printed circuit board traces that construct this current
loop need to have a small area and low inductance. To
control the inductance, short and wide traces must be
used.
Figure 5-2 depicts the current flow paths when the
outputs of the MCP14628 are low and the power
MOSFETs are turned off. These current paths should
also have low inductance and a small loop area to
minimize voltage ringing and spiking.
FIGURE 5-2: Turn Off Current Paths.
The following recommendations should be followed to
allow for optimal circuit performance.
- The components that construct the high
current paths previously mentioned should be
placed close the MCP14628. The traces
used to construct these current loops should
be wide and short to keep the inductance and
impedance low.
- A ground plane should be used to keep both
the parasitic inductance and impedance
minimized. The MCP14628 is capable of
sourcing and sinking high peaks current and
any extra parasitic inductance or impedance
will result in non-optimal performance.
V
CC
PWM
C
VCC
C
BOOT
V
SUPPLY
MCP14628
Control
Logic
V
CC
PWM
C
VCC
C
BOOT
V
SUPPLY
MCP14628
Control
Logic