MIC5011 Datasheet, PDF (10/12 Pages) Micrel Semiconductor – Minimum Parts High- or Low-Side MOSFET Driver

MIC5011
Applications Information (Continued)
12V
100kΩ
1N4148
+
47µF
10kΩ
+
10µF
MIC5011
1 _V+
C1 ⁸
2 _{Input Com} 7
3 _{Source C2} 6
4 _{Gnd Gate} 5
IRFZ44
100Ω
OUTPUT
(Delay=2.5s)
Figure 9. 30 Ampere
Time-Delay Relay
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 100kΩ/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 1kΩ 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.
Micrel
12V
R
330kΩ 330kΩ
MIC5011 ^10µF
1 _V+
C1 ⁸
2 _{Input Com} 7
3 _{Source C2} 6
4 _{Gnd Gate} 5
+
IRFZ44
1N4148
100nF
T
M
12V
START
RUN
STOP
Figure 10. Motor Stall
Shutdown
15V
330kΩ
330kΩ
+
MIC5011 ^10µF
1 _V+
C1 ⁸
2 _{Input Com} 7 _1nF
3 _{Source C2} 6
4 _{Gnd Gate} 5
IRF541
1N4148
100nF
15V
T
M
1kΩ
Figure 11. Electronic Governor
MIC5011
10
July 2000