MIC4100BM Micrel Inc, MIC4100BM Datasheet - Page 15

• Manufacturer Part Number: MIC4100BM
• Description: IC,Dual MOSFET Driver,SOP,8PIN,PLASTIC
• Manufacturer: Micrel Inc

Specifications of MIC4100BM

• Configuration: Half Bridge
• Input Type: Non-Inverting
• Delay Time: 27ns
• Current - Peak: 2A
• Number Of Configurations: 1
• Number Of Outputs: 2
• High Side Voltage - Max (bootstrap): 118V
• Voltage - Supply: 9 V ~ 16 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

capacitors are recommended for most applications. The
minimum capacitance value should be increased if low
voltage capacitors are use since even good quality
dielectric capacitors, such as X5R, will lose 40% to 70% of
their capacitance value at the rated voltage.
Placement of the decoupling capacitors is critical. The
bypass capacitor for Vdd should be placed as close as
possible between the Vdd and Vss pins.
capacitor (C
close as possible between the HB and HS pins. The etch
connections must be short, wide and direct. The use of a
ground plane to minimize connection impedance is
recommended. Refer to the section on layout and
component placement for more information.
The voltage on the bootstrap capacitor drops each time it
delivers charge to turn on the MOSFET. The voltage drop
depends on the gate charge required by t
Most MOSFET specifications specify gate charge vs. Vgs
voltage. Based on this information and a recommended
∆V
capacitance is calculated as:
The decoupling capacitor for the Vdd input may be
calculated in with the same formula; however, the two
capacitors are usually equal in value.
Grounding, Component Placement and Circuit Layout
Nanosecond switching speeds and am
in and around the MIC4100 and MIC4101 drivers require
proper placement and trace routing of all components.
Improper placement may cause degraded noise immunity,
false switching, excessive ringing or circuit latch-up.
Figure 9 shows the critical current paths when the driver
outputs go high and turn on the external MOSFETs. It also
helps demonstrate the need for a low impedance g
plane. Charge needed to turn-on the MOSFET gates
comes from the decoupling capacitors C
Current in the low-side gate driver flows from C
the internal driver, into the MOSFET gate and out the
Source. The return connection back to the decoupling
capacitor is made through the ground plane. Any
inductance or resistance in the ground return path causes
a voltage spike or ringing to appear on the source of the
MOSFET. This voltage works against the gate drive
voltage and can either slow down or turn off the MOSFET
during the period where it should be turned on.
Current in the high-side driver is sourced from capacitor C
and flows into the HB pin and out the HO pin, into the gate
of the high side MOSFET. The return path for
Micrel, Inc.
March 2006
HB
of less than 0.1V, the minimum value of bootstrap
C
where
B
≥
B
∆
Q
) for the HB supply pin must be located as
:
V
∆V
Q
gate
HB
gate
HB
=
=
Total
Voltage
Gate
drop
Charge
at the
pere peak currents
at
HB
V
he MOSFET.
VDD
The bypass
HB
VDD
the current
pin
and C
through
round
B
B
.
15
is from the source of the MOSFET and back to capacitor
C
a low impedance ground plane so the etch connections in
this critical path should be short and wide to minimize
parasitic
impedance between the MOSFET source and the
decoupling capacitor causes negative voltage feedback
which fights the turn-on of the MOSFET.
It is important to note that capacitor CB must be placed
close to the HB and HS pins. This capacitor not only
provides all the energy for turn-on but it m
pin noise and ripple low for proper operation of the high-
side drive circuitry.
Figure 10 shows the critical cu
outputs g
lo
for the same reasons given in the turn-on explanation.
Current flowing through the internal diode replenishes
charge in the bootstrap capacitor, CB.
B
w impedance connections are important during turn-off
High-side drive turn-on
. The high-side circuit return path usually does not have
current path
plane
gnd
o low and turn
inductance.
Low-side drive turn-on
current path
C
Turn-On Current Paths
Vdd
C
B
Vdd
HB
HO
HS
As
off the ext
Figure 9
with
rren
ernal MOSFETs. Short,
t paths when the driver
Level
shift
the
low-side
ust also keep HB
Vss
LO
LO
LI
HI
M9999-031506
MIC4100/1
circuit,
plane
gnd