1997

4-3

MIC2171

Micrel

4

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)

• Predriver for higher power capability

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 applications,

the floating switch architecture of the MIC2171 makes it

practical for step-down, inverting, and Cuk configurations 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.

MIC2171

100kHz 2.5A Switching Regulator

Preliminary Information

Typical Applications

C4

470µF

D2

1N5818

C1

47µF

C2

1µF

R3

1k

R4*

5V, 0.5A

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

C3*

D1*

R1

3.74k

1%

R2

1.24k

1%

4V to 6V

T1

1:1.25

MIC2171

IN

SW

FB

GND

COMP

Figure 2.

MIC2171 5V Flyback Converter

+5V

(4.75V min.)

D1

1N5822

MIC2171

IN

SW

FB

C1*

47µF

R3

1k

C3

1µF

R1

10.7k

1%

C2

470µF

+12V, 0.25A

L1

15µH

* Locate near MIC2171 when supply leads > 2

"

R2

1.24k

1%

GND

COMP

Figure 1.

MIC2171 5V to 12V Boost Converter