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MIC2171

100kHz 2.5A Switching Regulator

Micrel 

MIC2171

100kHz 2.5A Switching Regulator

General Description

The MIC2171 is a complete 100kHz SMPS current-mode

controller with an internal 65V 2.5A power switch.

Although primarily intended for voltage step-up applica-

tions, the floating switch architecture of the MIC2171

makes it practical for step-down, inverting, and Cuk config-

urations as well as isolated topologies.

Operating from 3V to 40V, the MIC2171 draws only 7mA

of quiescent current, making it attractive for battery

operated supplies.

The MIC2171 is available in a 5-pin TO-220 or TO-263 for

–40°C to +85°C operation.

Data sheets and support documentation can be found on

Micrel’s web site at: www.micrel.com.

Features

• 2.5A, 65V internal switch rating

• 3V to 40V input voltage range

• Current-mode operation, 2.5A peak

• Internal cycle-by-cycle current limit

• Thermal shutdown

• Twice the frequency of the LM2577

• Low external parts count

• Operates in most switching topologies

• 7mA quiescent current (operating)

• Fits LT1171/LM2577 TO-220 and TO-263 sockets

Applications

• Laptop/palmtop computers

• Battery operated equipment

• Hand-held instruments

• Off-line converter up to 50W(requires external power

switch)

• Pre-driver for higher power capability

___________________________________________________________________________________________________________

Typical Application

+5V

(4.75V min.)

L1

15µH

C1*

47µF

IN

SW

MIC2171

D1

1N5822

VO U T

+12V, 0.25A

R1

10.7k

1%

COMP

FB

R3

1k

C3

GND

1µF

C2

470µF

R2

1.24k

1%

* Locate near MIC2171 when supply leads > 2”

Figure 1. MIC2171 5V to 12V Boost Converter

VIN

4V to 6V

C1

R4*

47µF

IN

SW

MIC2171

COMP

FB

R3

1k

GND

C2

1µF

VOU T

T1

5V, 0.5A

C3*

D2

1N5818

R1

C4 3.74k

D1*

470µF 1%

1:1.25

LP RI = 12µH

R2

1.24k

1%

* Optional voltage clipper (may be req’d if T1 leakage inductance too high)

Figure 2. MIC2171 5VFlyback Converter

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

May 2007

1

M9999-051107

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