MIC2570

Micrel

4-62

1997

MIC2570

Two-Cell Switching Regulator

Preliminary Information

General Description

Micrel’s MIC2570 is a micropower boost switching regulator

that operates from two alkaline, two nickel-metal-hydride

cells, or one lithium cell.

The MIC2570 accepts a positive input voltage between 1.3V

and 15V. Its typical no-load supply current is 130

µA.

The MIC2570 is available in selectable fixed output or adjust-

able output versions. The MIC2570-1 can be configured for

2.85V, 3.3V, or 5V by connecting one of three separate

feedback pins to the output. The MIC2570-2 can be config-

ured for an output voltage ranging between its input voltage

and 36V, using an external resistor network.

The MIC2570 has a fixed switching frequency of 20kHz. An

external SYNC connection allows the switching frequency to

be synchronized to an external signal.

The MIC2570 requires only four components (diode, induc-

tor, input capacitor and output capacitor) to implement a

boost regulator. A complete regulator can be constructed in

All versions are available in an 8-lead SOIC with an operating

range from –40

°C to +85°.

Typical Applications

Features

• Operates from a two-cell supply

1.3V to 15V operation

• 130

µA typical quiescent current

• 2.85V/3.3V/5V selectable output voltage (MIC2570-1)

• Adjustable output up to 36V (MIC2570-2)

• 1A current limited pass element

• Frequency synchronization input

• 8-lead SOIC package

Applications

• LCD bias generator

• Glucose meters

• Single-cell lithium to 3.3V or 5V converters

• Two-cell alkaline to

±5V converters

• Two-cell alkaline to –5V converters

• Battery-powered, hand-held instruments

• Palmtop computers

• Remote controls

• Detectors

• Battery Backup Supplies

Two-Cell to 5V DC-to-DC Converter

IN

SW

GND

MIC2570-1

C2

220µF

10V

5V/100mA

C1

100µF

10V

2.0V–3.1V

2 AA Cells

2.85V

3.3V

5V

2

4

5

6

1

7

8

L1

47µH

SYNC

D1

MBRA140

Single-Cell Lithium to 3.3V/80mARegulator

GND

3.3V

SW

MIC2570

SYNC

7

5

1

2

8

IN

C3

330µF

6.3V

3.3V/80mA

2.5V to 4.2V

1 Li Cell

C1

100µF

10V

D1

MBRA140

L1

50µH

L1

C2

100µF

10V

U1

12

3

4