MIC4600 Datasheet, PDF (16/26 Pages) Microchip Technology – 28V Half-Bridge MOSFET Driver

MIC4600
path for the current is from the source of the MOSFET
and back to capacitor C_B. The high-side circuit return
path usually does not have a low-impedance ground
plane so the etch connections in this critical path
should be short and wide to minimize parasitic
inductance. As with the low-side circuit, impedance
between the MOSFET source and the decoupling
capacitor causes negative voltage feedback that fights
the turn-on of the MOSFET.
It is important to note that capacitor C_B must be placed
close to the BST and SW pins. This capacitor not only
provides all the energy for turn-on but it must also keep
HB pin noise and ripple low for proper operation of the
high-side drive circuitry.
impedance between the MIC4600, the decoupling
capacitors, and the external MOSFET will degrade the
performance of the driver.
FIGURE 6-3:
Turn-On Current Paths.
Figure 6-4 shows the critical current paths when the
driver outputs go low and turn off the external
MOSFETs. Short, low-impedance connections are
important during turn-off for the same reasons given in
the turn-on explanation. Current flowing through the
internal diode replenishes charge in the bootstrap
capacitor, C_BST.
LOW-SIDE DRIVE
TURN-OFF CURRENT PATH
VDD
DL
C_VDD
BST
PGND
LSI
DH
C_B
Level
shift
HSI
SW
HIGH-SIDE DRIVE
TURN-OFF CURRENT PATH
MIC4600
FIGURE 6-4:
Turn-Off Current Paths.
Use a ground plane to minimize parasitic inductance
and impedance of the return paths. The MIC4600 is
capable of greater than 1A peak currents and any
DS20005584A-page 16
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