MIC4576

Micrel

MIC4576

4-128

April 1998•

MIC4576

200kHz Simple 3A Buck Voltage Regulator

General Description

The MIC4576 is a series of easy to use fixed and adjustable

BiCMOS step-down (buck) switch-mode voltage regulators.

The 200kHz MIC4576 duplicates the pinout and function of

the 52kHz LM2576. The higher switching frequency may

allow up to a 2:1 reduction in output filter inductor size.

The MIC4576 is available in 3.3V, and 5V fixed output

versions or a 1.23V to 33V adjustable output version. Both

versions are capable of driving a 3A load with excellent line

and load regulation.

The feedback voltage is guaranteed to

±2% tolerance for

adjustable versions, and the output voltage is guaranteed to

±3% for fixed versions, within specified voltages and load

conditions. The oscillator frequency is guaranteed to

±10%.

In shutdown mode, the regulator draws less than 200

µA

standby current.

The regulator performs cycle-by-cycle

current limiting and thermal shutdown for protection under

fault conditions.

This series of simple switch-mode regulators requires a

minimum number of external components and can operate

using a standard series of inductors. Frequency compensa-

tion is provided internally.

The MIC4576 is available in TO-220 (T) and TO-263 (U)

packages for the industrial temperature range.

Typical Applications

C1

470µF

63V

D1

MBR360

C2

1000µF

16V

L1

33µH

GND

FB

SW

MIC4576-5.0BT

SHDN

8V to 36V

5V/3A

3

4

2

5

1

Shutdown

Enable

Fixed Regulator

C1

470µF

63V

MBR360

C2

1000µF

16V

L1

68µH

GND

FB

SW

MIC4576BT

SHDN

16V to 36V

12V/3A

R2

13.0k

1%

R1

1.50k

1%

5

1

4

2

3

Shutdown

Enable

Adjustable Regulator

Features

• Fixed 200kHz operation

• 3.3V, 5V, and adjustable output versions

• Voltage over specified line and load conditions:

Fixed version:

±3% max. output voltage

Adjustable version:

±2% max. feedback voltage

• Guaranteed 3A switch current

• Wide 4V to 36V input voltage range

• Wide 1.23V to 33V output voltage range

• Requires minimum external components

• < 200

µA typical shutdown mode

• 75% efficiency (adjustable version > 75% typical)

• Standard inductors are 25% of typical LM2576 values

• Thermal shutdown

• Overcurrent protection

• 100% electrical thermal limit burn-in

Applications

• Simple high-efficiency step-down (buck) regulator

• Efficient preregulator for linear regulators

• On-card switching regulators

• Positive-to-negative converter (inverting buck-boost)

• Battery Charger

• Negative boost converter

• Step-down to 3.3V for Intel Pentium™

and similar microprocessors