MIC5012 Ver la hoja de datos (PDF) - Micrel

Número de pieza

componentes Descripción

Fabricante

MIC5012

Dual High- or Low-Side MOSFET Driver

Micrel 

MIC5012

Micrel

Applications Information (Continued)

12V

can be paralleled. This reduces the switch drop, and distrib-

utes the switch dissipation into multiple packages.

Half-Bridge Motor Driver (Figure 6). Closed loop control of

motor speed requires a half-bridge driver. This topology

presents an extra challenge since the two output devices

should not cross conduct (shoot-through) when switching.

Cross conduction increases output device power dissipa-

tion. Speed is also important, since PWM control requires

the outputs to switch in the 2 to 20kHz range.

100kΩ

1N4148

+

47µF

10kΩ

+

1/2 MIC5012 10µF

V+

Input

Source

Gnd Gate

IRFZ44

The circuit of Figure 6 utilizes fast configurations for both the

100Ω

top- and bottom-side drivers. Delay networks at each input

provide a 2 to 3µs dead time effectively eliminating cross

conduction. Two of these circuits can be connected to-

gether to form an H-bridge for locked antiphase or sign/

magnitude control.

OUTPUT

(Delay=2s)

Figure 7. 30 Ampere

Time-Delay Relay

Time-Delay Relay (Figure 7). The MIC5012 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.

Electronic Governor (Figure 9). 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 MIC5012.

When the motor is stalled there is no tachometer output,

and MIC5012 input is pulled high delivering full power to the

motor. If the motor spins fast enough, the tachometer output

Motor Driver with Stall Shutdown (Figure 8). Tachometer is sufficient to pull the MIC5012 input low, shutting the

feedback can be used to shut down a motor driver circuit output off. Since the rectified waveform is only partially

when a stall condition occurs. The control switch is a 3-way filtered, the input oscillates around its threshold causing the

type; the “START” position is momentary and forces the MIC5012 to switch on and off at the frequency of the

5

driver ON. When released, the switch returns to the “RUN” tachometer signal. A PWM action results since the average

position, and the tachometer's output is used to hold the dc voltage at the input decreases as the motor spins faster.

MIC5012 input ON. If the motor slows down, the tach output The 1kΩ potentiometer is used to set the running speed of

is reduced, and the MIC5012 switches OFF. Resistor “R” the motor. Loop gain (and speed regulation) is increased by

sets the shutdown threshold.

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

12V

controller and a half-bridge.

R

330kΩ 330kΩ

1/2 MIC5012 10µF

V+

Input

Source

Gnd Gate

+

IRFZ44

1N4148

100nF

T

M

12V

START

RUN

STOP

Figure 8. Motor Stall

Shutdown

15V

330kΩ

330kΩ

1/2 MIC5012 10µF

V+

Input

Source

Gnd Gate

+

IRF541

1N4148

100nF

15V

T

M

1kΩ

Figure 9. Electronic Governor

April 1998

5-121

Share Link: