MIC5011 Micrel Semiconductor, MIC5011 Datasheet - Page 10

• Manufacturer Part Number: MIC5011
• Description: Minimum Parts High- or Low-Side MOSFET Driver
• Manufacturer: Micrel Semiconductor

MIC5011
Applications Information
Time-Delay Relay (Figure 9). The MIC5011 forms the
basis of a simple time-delay relay. As shown, the delay
commences when power is applied, but the 100k /1N4148
could be independently driven from an external source such
as a switch or another high-side driver to give a delay
relative to some other event in the system. Hysteresis has
been added to guarantee clean switching at turn-on.
Motor Driver with Stall Shutdown (Figure 10). Tachom-
eter feedback can be used to shut down a motor driver
circuit when a stall condition occurs. The control switch is a
3-way type; the “START” position is momentary and forces
the driver ON. When released, the switch returns to the
“RUN” position, and the tachometer's output is used to hold
the MIC5011 input ON. If the motor slows down, the tach
output is reduced, and the MIC5011 switches OFF. Resis-
tor “R” sets the shutdown threshold.
Electronic Governor (Figure 11). The output of an ac
tachometer can be used to form a PWM loop to maintain the
speed of a motor. The tachometer output is rectified,
partially filtered, and fed back to the input of the MIC5011.
When the motor is stalled there is no tachometer output,
and MIC5011 input is pulled high delivering full power to the
motor. If the motor spins fast enough, the tachometer output
is sufficient to pull the MIC5011 input low, shutting the
output off. Since the rectified waveform is only partially
filtered, the input oscillates around its threshold causing the
MIC5011 to switch on and off at the frequency of the
tachometer signal. A PWM action results since the average
dc voltage at the input decreases as the motor spins faster.
The 1k potentiometer is used to set the running speed of
the motor. Loop gain (and speed regulation) is increased by
increasing the value of the 100nF filter capacitor.
The performance of such a loop is imprecise, but stable and
inexpensive. A more elaborate loop would consist of a PWM
controller and a half-bridge.
MIC5011
100k
47µF
100
+
10k
1N4148
Figure 9. 30 Ampere
Time-Delay Relay
1
2
3
4
V+
Source
Gnd
Input
MIC5011
Gate
Com
(Continued)
C2
C1
10µF
8
7
6
5
(Delay=2.5s)
OUTPUT
+
12V
IRFZ44
10
330k
R
330k
100nF
Figure 11. Electronic Governor
1N4148
330k
330k
100nF
START
STOP
Figure 10. Motor Stall
RUN
1k
1
2
3
4
15V
V+
Input
Source
Gnd
1
2
3
4
Shutdown
1N4148
MIC5011
V+
Source
Gnd
12V
Input
MIC5011
Gate
Com
T
C2
C1
Com
Gate
T
C2
C1
8
7
6
5
10µF
8
7
6
5
10µF
1nF
+
15V
M
+
IRF541
12V
July 2000
M
IRFZ44
Micrel