July 2005

9

MIC5011

MIC5011

Micrel, Inc.

Input

Source

Gate

1

2

3

4

8

MIC5011

7

6

5

V+

Gnd

C1

Com

C2

IRF541

1µF

+

100nF

1N4001 (2)

1N5817

15V

220pF

1N4148

22kΩ

10A Stalled

Input

Source

Gate

1

2

3

4

8

MIC5011

7

6

5

V+

Gnd

C1

Com

C2

IRF541

10µF

+

1nF

10kΩ

2N3904

22kΩ

15V

PWM

INPUT

Input

Source

Gate

1

2

3

4

8

MIC5011

7

6

5

V+

Gnd

C1

Com

C2

IRFP250

100µF

+

90V

M

1nF

15V

1N4003 (2)

1N4003

100kΩ

1kΩ

100kΩ

4N35

33kΩ

33pF

MPSA05

10mA

Control Input

15Vp-p, 20kHz

Squarewave

1N4746

100nF

200V

1/4 HP, 90V

5BPB56HAA100

(GE)

diode limits the supply to 18V. When the MIC5011 is off,

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

circuit of Figure 5 is put to good use as a barrier between

low voltage control circuitry and the 90V motor supply.

Half-Bridge Motor Driver (Figure 8). 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.

The circuit of Figure 8 utilizes fast configurations for both

the 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

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

magnitude control.

Figure 7. High-Voltage

Bootstrapped Driver

Figure 8. Half-Bridge

Motor Driver