MIC38C42/3/4/5

Micrel, Inc.

M9999-091107

8

September 2007

Symbol

CT1

4923

ETS 92420

T1

4924

ETS 92419

L1

4925

ETS 92421

1. Custom Coils, Alcester, SD tel: (605) 934-2460

2. Energy Transformation Systems, Inc. tel: (415) 324-4949.

Test

Conditions

Results

0.5%

0.6%

Efficiency

90%

Output Ripple

100mV

Synchronous Buck Converter

Refertofigure2. ThisMIC38C43synchronousbuckconverter

uses an MIC5022 half-bridge driver to alternately drive the

PWMswitchMOSFET(drivenbyGATEH,orhigh-sideoutput)

and a MOSFET which functions as a synchronous rectifier

(driven by the GATEL, or low-side output).

The low-side MOSFET turns on when the high-side MOS-

FET is off, allowing current to return from ground. Current

flows through the low-side MOSFET in the source to drain

direction.

The on-state voltage drop of the low-side MOSFET is lower

than the forward voltage drop of an equivalent Schottky recti-

fier. This lower voltage drop results in higher efficiency.

A sense resistor (5mΩ) is connected to the driver’s high-

side current sense inputs to provide overcurrent protection.

Refer to the MIC5020, MIC5021, and MIC5022 data sheets

for more information.

Figure 2. 100kHz, Synchronous Buck Converter

MIC38C43

0.1µF

300k

4.3k

5V, 8A

0.15µF

35µH

1000µF

Low ESR

0.1µF

SMP60N06-14

VDD

V R E F

GND

COM P

VOUT

RT/CT

F B

I S N S

4.7nF

10k

10k

6.8k

47k

3.3k

2200

pF

470µF

25V

MIC5022

VB

GAT E H

SH+

GAT E L

SH–

SL+

C T

GND

E N

FLT

VDD

+12V

5mΩ

0.1µF*

MKS2

*Locate near the MIC38C43 supply pins.

NC

NC

IN

NC

S L–