MIC5019 Datasheet, PDF (8/12 Pages) Micrel Semiconductor – Ultra-Small High-Side N-Channel MOSFET Driver with Integrated Charge Pump

Micrel, Inc.
MIC5019
Figure 3. Using a Logic-Level MOSFET
Refer to Figure 3 for an example showing nominal
voltages. The maximum gate-to-source voltage rating of
some of the logic-level MOSFET can be ±10V; this can
be exceeded if a higher supply voltage is used. An
external zener diode can clamp the gate-to-source
voltage as shown in Figure 4. The zener voltage, plus its
tolerance, must not exceed the absolute maximum gate
voltage of the MOSFET.
Figure 5. Switching an Inductive Load
Switching off an inductive load in a high-side application
momentarily forces the MOSFET source negative (as
the inductor opposes changes to current). This voltage
spike can be very large and can exceed a MOSFET’s
gate-to-source and drain-to-source ratings. A Schottky
diode across the inductive load provides a discharge
current path to minimize the voltage spike. The peak
current rating of the diode should be greater than the
load current.
In a low-side application, switching off an inductive load
will momentarily force the MOSFET drain higher than the
supply voltage. The same precaution applies.
Split Power Supply
Refer to Figure 6. The MIC5019 can be used to control a
12V load by separating the driver supply from the load
supply.
Figure 4. Gate-to-Source Protection
A gate-to-source zener may also be required when the
maximum gate-to-source voltage could be exceeded due
to normal part-to-part variation in gate output voltage.
Other conditions can momentarily increase the gate-to-
source voltage, such as turning on a capacitive load or
shorting a load.
Inductive Loads
Inductive loads include relays, and solenoids. Long
leads may also have enough inductance to cause
adverse effects in some circuits.
Figure 6. 12V High-Side Switch
July 2012
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