mic4104yml Micrel Semiconductor, mic4104yml Datasheet - Page 10

• Manufacturer Part Number: mic4104yml
• Description: 100v Half Bridge Mosfet Drivers 3/2a Sinking/sourcing Current
• Manufacturer: Micrel Semiconductor

The MIC4104 has a TTL compatible input range and is
recommended for use with inputs signals whose amplitude
is less than the supply voltage. The threshold level is
independent of the VDD supply voltage and there is no
dependence between I
with the MIC4104. This feature makes the MIC4104 an
excellent level translator that will drive high threshold
MOSFETs from a low voltage PWM IC.
Low-Side Driver
A block diagram of the low-side driver is shown in Figure
3. The low-side driver is designed to drive a ground (V
pin)
impedances allow the external MOSFET to be turned on
and off quickly. The rail-to-rail drive capability of the output
ensures full enhancement of the external MOSFET.
A high level applied to LI pin causes the upper driver FET
to turn on and V
external MOSFET. A low level on the LI pin turns off the
upper driver and turns on the low side driver to ground the
gate of the external MOSFET.
High-Side Driver and Bootstrap Circuit
A block diagram of the high-side driver and bootstrap
circuit is shown in Figure 4. This driver is designed to drive
a floating N-channel MOSFET, whose source terminal is
referenced to the HS pin.
Micrel
October 2007
Figure 2. MIC4103 Supply Current vs. Input Voltage
referenced
Figure 3. Low-Side Driver Block Diagram
Vss
DD
Vdd
N-channel
voltage is applied to the gate of the
VDD
LO
and the input signal amplitude
MOSFET.
External
FET
Low
driver
SS
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
synchronous buck converter shown in Figure 5, the HS pin
is at ground potential while the low-side MOSFET is on.
The internal diode allows capacitor C
V
drop of the internal diode). After the low-side MOSFET is
turned off and the HO pin turns on, the voltage across
capacitor C
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
diode is reverse biased preventing capacitor C
discharging.
Figure 4. High-Side Driver and Bootstrap Circuit Block
DD
C
-V
Figure 5. High-Side Driver and Bootstrap Circuit
VDD
HI
LI
D
during this time (where V
Level
shift
B
Vdd
IN
is applied to the gate of the upper external
. As the HS and HB pin rise, the internal
Vss
B
. In a typical application, such as the
HB
Diagram
HO
C
HS
LO
B
D
is the forward voltage
Vin
B
Q1
Q2
to charge up to
M9999-100107-B
MIC4103/4104
Lout
B
from