MIC5010

Micrel

5-98

April 1998

Inhibit

Input

Thresh

Sense

Source

Gnd

Fault

V+

C1

Com

C2

Gate

1

2

3

4

5

6

78

9

10

11

12

13

14

MIC5010

IRFP044 (2)

10µF

20k

Ω

Figure 9. 50-Ampere

Industrial Switch

+

NC

NC

100

Ω

5m

Ω

LOAD

24V

15k

Ω

OFF

330k

Ω

100k

Ω

ON

24V

LVF-15 (RCD)

CR2943-NA102A

(GE)

extends out from the control box, is more easily pressed.

This circuit is compatible with control boxes such as the

CR2943 series (GE). The circuit is configured so that if both

switches close simultaneously, the “off” button has prece-

dence. If there is a fault condition the circuit will latch off, and

it can be reset by pushing the “on” button.

This application also illustrates how two (or more) MOSFETs

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

utes the switch dissipation into multiple packages.

High-Voltage Bootstrap (Figure 10). Although the MIC5010

is limited to operation on 7 to 32V supplies, a floating

bootstrap arrangement can be used to build a high-side

switch that operates on much higher voltages. The MIC5010

and MOSFET are configured as a low-side driver, but the

load is connected in series with ground. The high speed

normally associated with low-side drivers is retained in this

circuit.

Power for the MIC5010 is supplied by a charge pump. A

20kHz square wave (15Vp-p) drives the pump capacitor

and delivers current to a 100

µF storage capacitor. A zener

diode limits the supply to 18V. When the MIC5010 is off,

power is supplied by a diode connected to a 15V supply.

The circuit of Figure 8 is put to good use as a barrier

between low voltage control circuitry and the 90V motor

supply.

Half-Bridge Motor Driver (Figure 11). 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 and, in the case of the MIC5010, could trip the over-

current comparator. Speed is also important, since PWM

control requires the outputs to switch in the 2 to 20kHz

range.

The circuit of Figure 11 utilizes fast configurations for both

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

input provide a 2 to 3

µs dead time effectively eliminating

occurs, the circuit breaker shuts off. The breaker tests the

load every 18ms until the short is removed, at which time the

circuit latches ON. No reset button is necessary.

Opto-Isolated Interface (Figure 8). Although the MIC5010

has no special input slew rate requirement, the lethargic

transitions provided by an opto-isolator may cause oscilla-

tions on the rise and fall of the output. The circuit shown

accelerates the input transitions from a 4N35 opto-isolator

by adding hysteresis. Opto-isolators are used where the

control circuitry cannot share a common ground with the

MIC5010 and high-current power supply, or where the

control circuitry is located remotely. This implementation is

intrinsically safe; if the control line is severed the MIC5010

will turn OFF.

Fault-Protected Industrial Switch (Figure 9). The most

common manual control for industrial loads is a push button

on/off switch. The “on” button is physically arranged in a

recess so that in a panic situation the “off” button, which

100k

Ω

Figure 8. Improved

Opto-Isolator Performance

1k

Ω

To MIC5010 Input

100k

Ω

4N35

33k

Ω

33pF

MPSA05

15V

10mA

Control Input