MIC4103_10 Datasheet, PDF (10/18 Pages) Micrel Semiconductor – 100V Half Bridge MOSFET Drivers 3/2A Sinking/Sourcing Current

Micrel
MIC4103/4104
Functional Description
The MIC4103 is a high-voltage, non-inverting, dual
MOSFET driver that is designed to independently drive
both high-side and low-side N-Channel MOSFETs. The
block diagram of the MIC4103 is shown in Figure 1.
Both drivers contain an input buffer with hysteresis, a
UVLO circuit and an output buffer. The high-side output
buffer includes a high-speed level-shifting circuit that is
referenced to the HS pin. An internal diode is used as part
of a bootstrap circuit to provide the drive voltage for the
high-side output.
Startup and UVLO
The UVLO circuit forces the driver output low until the
supply voltage exceeds the UVLO threshold. The low-side
UVLO circuit, monitors the voltage between the VDD and
VSS pins. The high-side UVLO circuit monitors the voltage
between the HB and HS pins. Hysteresis in the UVLO
circuit prevents noise and finite circuit impedance from
causing chatter during turn-on.
Input Stage
The MIC4103 and MIC4104 have different input stages,
which lets these parts cover a wide range of driver
applications. Both the HI and LI pins are referenced to the
VSS pin.
The MIC4103 has a high-impedance, CMOS compatible
input threshold and is recommended for applications
where the input signal is noisy or where the input signal
swings the full range of voltage (from V_DD to GND). There
is typically 400mV of hysteresis on the input pins
throughout the V_DD range. The hysteresis improves noise
immunity and prevents input signals with slow rise times
from falsely triggering the output. The threshold voltage of
the MIC4103 varies proportionally with the V_DD supply
voltage.
The amplitude of the input signal affects the VDD supply
current. V_IN voltages that are a diode drop less than the
V_DD supply voltage will cause an increase in the VDD pin
current. The graph in Figure 2 shows the typical
dependence between I_VDD and V_IN for V_DD = 12V.
Figure 2. MIC4103 Supply Current vs. Input Voltage
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_VDD and the input signal amplitude
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 (VSS
pin) referenced N-channel MOSFET. Low driver
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_DD voltage is applied to the gate of the
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.
Vdd
External
FET
LO
November 2010
Vss
Figure 3. Low-Side Driver Block Diagram
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M9999-110910-B