MIC5014/5015

Micrel

5-144

1997

Motor Driver With Stall Shutdown (Figure 10) 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 MIC5014 input ON.

If the motor slows down, the tach output is reduced, and the

MIC5014 switches OFF. Resistor “R” sets the shutdown

threshold.

Figure 10. Motor Stall Shutdowm

Simple DC-DC Converter (Figure 11) The simplest applica-

tion for the MIC5014 is as a basic one-chip DC-DC converter.

As the output (Gate) pin has a relatively high impedance, the

output voltage shown will vary significantly with applied load.

Incandescent/Halogen Lamp Driver (Figure 8) The combi-

nation of an MIC5014/5015 and a power FET makes an

effective driver for a standard incandescent or halogen lamp

load. Such loads often have high inrush currents, as the

resistance of a cold filament is less than one-tenth as much as

when it is hot.

Power MOSFETs are well suited to this

application as they have wider safe operating areas than do

power bipolar transistors. It is important to check the SOA

curve on the data sheet of the power FET to be used against

the estimated or measured inrush current of the lamp in

question prior to prototyping to prevent “explosive” results.

If overcurrent sense is to be used, first measure the duration

of the inrush, then use the topology of Figure 5 with the RC of

the timer chosen to accomodate the duration with suitable

guardbanding.

Figure 8. Halogen Lamp Driver

Relay Driver (Figure 9) Some power relay applications re-

quire the use of a separate switch or drive control, such as in

the case of microprocessor control of banks of relays where

a logic level control signal is used, or for drive of relays with

high power requirements. The combination of an MIC5014/

5015 and a power FET also provides an elegant solution to

power relay drive.

Figure 9: Relay Driver

MIC5014

Control Input

OFF

ON

1

2

3

4

8

7

6

5

IRF540

12V

NC

Gate

Gnd

Source

Input

V+

NC

NC

10µF

OSRAM

HLX64623

MIC5014

Control Input

OFF

ON

1

2

3

4

8

7

6

5

IRF540

12V

NC

Gate

Gnd

Source

Input

V+

NC

NC

10µF

Guardian Electric

1725-1C-12D

MIC5014

1

2

3

4

8

7

6

5

IRFZ44

12V

NC

Gate

Gnd

Source

Input

V+

NC

NC

10µF

M

T

R

330k

Ω

330k

Ω

1N4148

Figure 11. DC - DC Converter

MIC5014

1

2

3

4

8

7

6

5

NC

Gate

Gnd

Source

Input

V+

NC

NC

10µF

5V