MIC4102_11 MIC [MIC GROUP RECTIFIERS], MIC4102_11 Datasheet - Page 10

• Manufacturer Part Number: MIC4102_11
• Description: 100V Half Bridge MOSFET Driver with Anti-Shoot Through Protection PRELIMINARY SPECIFICATIONS
• Manufacturer: MIC [MIC GROUP RECTIFIERS]

High-Side Driver and Bootstrap Circuit
A block diagram of the high-side driver and bootstrap
circuit is shown in Figure 3. This driver is designed to
drive a floating N-channel MOSFET, whose source
terminal is referenced to the HS pin.
Micrel, Inc.
November 2006
LS
C
B
Figure 3. High-Side Driver Block Diagram
Figure 2. Low-Side Driver Block Diagram
Signal
Drive
Vdd
Vss
HS
Vdd
HB
HO
LO
External
External
FET
FET
10
A low power, high speed, level shifting circuit isolates the
low side (VSS pin) referenced circuitry from the high-
side (HS pin) referenced driver. Power to the high-side
driver and UVLO circuit is supplied by the bootstrap
circuit while the voltage level of the HS pin is shifted
high.
The bootstrap circuit consists of an internal diode and
external capacitor, C
the synchronous buck converter shown in Figure 4, the
HS pin is at ground potential while the low-side MOSFET
is on. The internal diode allows capacitor C
up to V
voltage drop of the internal diode). After the low-side
MOSFET is turned off and the HO pin turns on, the
voltage across capacitor C
upper external MOSFET. As the upper MOSFET turns
on, voltage on the HS pin rises with the source of the
high-side MOSFET until it reaches V
HB pin rise, the internal diode is reverse biased
preventing capacitor C
PWM
C
VDD
Figure 4. High-Side Driver and Bootstrap Circuit
DD
FF
-V
Q
Q
_
Level
shift
Vdd
D
during this time (where V
Vss
B
HB
. In a typical application, such as
B
from discharging.
HO
C
HS
LO
B
B
is applied to the gate of the
Vin
Q1
Q2
IN
. As the HS and
D
Lout
M9999-112806
is the forward
B
MIC4102
to charge
Cout
Vout