MIC5060_10 Datasheet, PDF (10/12 Pages) Micrel Semiconductor – Ultra Small High-Side MOSFET Driver

Micrel, Inc.
Typical Applications
Variable Supply Low Side Driver for Motor Speed
Control
The internal regulation in the MIC5060 allows a steady
gate enhancement to be supplied while the MIC5060
supply varies from 5V to 30V, without damaging the
internal gate to source zener clamp. This allows the
speed of the DC motor shown to be varied by varying
the supply voltage.
MIC5060
Figure 5. DC Motor Speed Control/Driver
Solenoid Valve Driver
High power solenoid valves are used in many industrial
applications requiring the timed dispensing of chemicals
or gases. When the solenoid is activated, the valve
opens (or closes), releasing (or stopping) fluid flow. A
solenoid valve, like all inductive loads, has a
considerable “kickback” voltage when turned off, as
current cannot change instantaneously through an
inductor. In most applications, it is acceptable to allow
this voltage to momentarily turn the MOSFET back on as
a way of dissipating the inductor’s current. However, if
this occurs when driving a solenoid valve with a fast
switching speed, chemicals or gases may be
inadvertently be dispensed at the wrong time with
possibly disastrous consequences. Also, too large of a
kickback voltage (as is found in larger solenoids) can
damage the MIC5060 or the power FET by forcing the
Source node below ground (the MIC5060 can be driven
up to 20V below ground before this happens). A catch
diode has been included in this design to provide an
alternate route for the inductive kickback current to flow.
The 5kΩ resistor in series with this diode has been
included to set the recovery time of the solenoid valve.
Figure 6. Solenoid Valve Driver
Incandescent/Halogen Lamp Driver
The combination of an MIC5060 and a power FET
makes an effective driver for a standard incandescent or
halogen lamp load. Such loads often have high inrush
currents, as the resistance of a cold filament is less than
one-tenth as much as when it is hot. Power MOSFETs
are well suited to this application as they have wider safe
operating areas than do power bipolar transistors. It is
important to check the SOA curve on the data sheet of
the power FET to be used against the estimated or
measured inrush current of the lamp in question prior to
prototyping to prevent “explosive” results.
Figure 7. Halogen Lamp Driver
February 2010
10
M9999-021610-C