MIC5014 Micrel Semiconductor, MIC5014 Datasheet - Page 7

• Manufacturer Part Number: MIC5014
• Description: Low-Cost High- or Low-Side MOSFET Driver
• Manufacturer: Micrel Semiconductor

MIC5014/5015
Typical Applications
Variable Supply Low Side Driver for Motor Speed Control
(Figure 6) The internal regulation in the MIC5014/15 allows
a steady gate enhancement to be supplied while the
MIC5014/15 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.
Solenoid Valve Driver (Figure 7) 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
1997
Figure 6: DC Motor Speed Control/Driver
OFF
ON
1
2
3
4
V+
Input
Source
Gnd
MIC5014
10µF
Figure 5. High Side Driver with Delayed Overcurrent Shutdown
Gate
NC
NC
NC
1k
V
8
7
6
5
CC
1
2
3
4
= +5V to +30V
V+
Input
Source
Gnd
M
MIC5014
IRF540
Gate
NC
NC
NC
8
7
6
5
R
0.06
S
1k
R4
12V
5-143
1000pF
R1
1k
R2
120k
applications, it is acceptable to allow this voltage to momen-
tarily 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 inadvertantly be dispensed at the wrong time
with possibly disasterous consequences. Also, too large of
a kickback voltage (as is found in larger solenoids) can
damage the MIC5014 or the power FET by forcing the Source
node below ground (the MIC5014 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 5k resistor in series
with this diode has been included to set the recovery time of
the solenoid valve.
On
LM301A
OFF
ON
0.01µF
Figure 7: Solenoid Valve Driver
1
2
3
4
2.2k
Gnd
Trigger
V
R/C
REF
LM3905N
12V
1
2
3
4
Input
Source
Gnd
V+
Logic
Emit
Coll
MIC5015
V+
8
7
6
5
Gate
NC
NC
NC
Solenoid
8
7
6
5
8320A
ASCO
24V
IRFZ40
5k
1N4005
Micrel
5