MIC5013_05 Datasheet, PDF (12/15 Pages) Micrel Semiconductor – Protected High- or Low-Side MOSFET Driver

MIC5013
Micrel, Inc.
Applications Information (Continued)
The top-side driver is based on the bootstrapped circuit of
Figure 6, and cannot be switched on indefinitely. The boot-
strap capacitor (1µF) relies on being pulled to ground by the
bottom-side output to recharge. This limits the maximum
duty cycle to slightly less than 100%.
Two of these circuits can be connected together to form
an H-bridge. If the H-bridge is used for locked antiphase
control, no special considerations are necessary. In the case
of sign/magnitude control, the “sign” leg of the H-bridge
should be held low (PWM input held low) while the other
leg is driven by the magnitude signal.
If current feedback is required for torque control, it is avail-
able in chopped form at the bottom-side driver's 22 mΩ
current-sensing resistor.
Time-Delay Relay (Figure 12). The MIC5013 forms the
basis of a simple time-delay relay. As shown, the delay
commences when power is applied, but the 100 kΩ/1N4148
could be independently driven from an external source such
as a switch or another high-side driver to give a delay rela-
tive to some other event in the system.
Hysteresis has been added to guarantee clean switching
at turn-on. Note that an over-current condition latches the
relay in a safe, OFF condition. Operation is restored by
either cycling power or by momentarily shorting pin 1 to
ground.
Motor Driver with Stall Shutdown (Figure 13). Tachometer
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
MIC5013 input ON. If the motor slows down, the tach output
is reduced, and the MIC5013 switches OFF. Resistor “R”
sets the shutdown threshold. If the output current exceeds
30A, the MIC5013 shuts down and remains in that condition
until the momentary “RESET” button is pushed. Control is
then returned to the START/RUN/STOP switch.
15V
100nF
1N5817
1N4148
22kΩ
220pF
20kΩ
MIC5013
1 _{Input Fault} 8
2 _{Thresh V+} 7
3 _{Sense Gate} 6
4 _{Source Gnd} 5
1N4001 (2)
+
1µF
IRF541
100Ω
22mΩ
CPSL-3
(Dale)
15kΩ
PWM
INPUT
22kΩ
2N3904
M
12V,
10A Stalled
15V
10kΩ
1nF
10kΩ
MIC5013
1 _{Input Fault} 8
2 _{Thresh V+} 7
3 _{Sense Gate} 6
4 _{Source Gnd} 5
+
10µF
IRF541
22mΩ
CPSL-3
(Dale)
Figure 11. Half-Bridge
Motor Driver
MIC5013
12
July 2005