July 2005

9

MIC5022

MIC5022

Micrel, Inc.

11

12

12

11

Input

Fault

Enable

Gnd

Gate H

Sense H–

Sense H+

Gate L

Sense L–

Sense L+

10µF

0.01µF

M

+12V to +20V

MIC5022

1

2

3

4

5

6

7

14

13

10

9

8

Input

Fault

Enable

Gnd

Gate H

Sense H–

Sense H+

Gate L

Sense L–

Sense L+

10µF

MIC5022

1

2

3

4

5

6

7

14

13

10

9

8

0.01µF

TTL Input

(PWM signal)

TTL Input

(PWM signal)

Figure 2. Full-Bridge Motor Control Application

Synchronous Rectifier Converter

The MIC5022 can be part of a synchronous rectifier in SMPS

(switch mode power supply) applications.

This circuit uses the MIC38C43 SMPS controller IC to switch

a pass transistor (Q1) and a “synchronous rectifier” transistor

(Q2) using the MIC5022.

The MIC38C43 controller switches the transistors at 50kHz.

Output regulation is maintained using PWM. When the pass

transistor is on, the synchronous rectifier is off and current is

forced through the inductor to the output capacitor and load.

When the pass transistor is switched off, the synchronous

rectifier is switched on allowing current to continue to flow

as the inductor returns stored energy.

The synchronous rectifier MOSFET has a lower voltage drop

than the forward voltage drop across a Schottky diode. This

increases converter efficiency which extends battery life in

portable equipment.

Figure 3. 50kHz Synchronous Rectifier Converter

MIC38C43

0.1µF

300k

4.3k

5V, 8A

0.15µF

70µH

1000µF

Low ESR

0.1µF

SMP06N06-14

Gnd

Comp

FB

4.7nF

10k

10k

13k

47k

3.3k

2200pF

470µF

25V

MIC5022

Gate H

S H+

Gate L

S H–

Fault

S L–

S L+

Gnd

Input

Enable

V+

+12V

5

1

8

2

9

7

12

11

3

10

14

13

2

1

4

3

8

5

7

6

5mΩ

Q1

Q2