MICREL MIC2570-1BM, MIC2570-2BM Datasheet

MIC2570 Micrel

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 130µA.

The MIC2570 is available in selectable fixed output or adjust­able 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 config­ured 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, induc­tor, input capacitor and output capacitor) to implement a
boost regulator. A complete regulator can be constructed in
a 0.6 in2 area.

All versions are available in an 8-lead SOIC with an operating
range from –40°C to +85°.

Features

• Operates from a two-cell supply

1.3V to 15V operation

• 130µA typical quiescent current

• Complete regulator fits 0.6 in2 area

• 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

T ypical Applications

2.0V–3.1V
2 AA Cells

C1
100µF
10V

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

MIC2570-1

SYNC

7

L1

47µH

8

IN

SW

2.85V

3.3V
5V

GND

2

MBRA140

1
6
5
4

D1

5V/100mA

C2
220µF
10V

2.5V to 4.2V
1 Li Cell

C1

100µF

10V

U1

12

IN

MIC2570

SYNC

GND

7

8

L1

50µH

SW

3.3V

2

C2

100µF

10V

MBRA140

3

D1

1

5

L1

4

3.3V/80mA

C3
330µF

6.3V

V

OUT

Single-Cell Lithium to 3.3V/80mARegulator

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MIC2570 Micrel

Ordering Information

Part Number Temperature Range Voltage Frequency Package

MIC2570-1BM –40°C to +85°C Selectable* 20kHz 8-lead SOIC
MIC2570-2BM –40°C to +85°C Adjustable 20kHz 8-lead SOIC

* Externally selectable for 2.85V, 3.3V, or 5V

Pin Configuration

MIC2570-1

SW

GND

NC

5V

1
2
3
4

8
7
6
5

IN
SYNC

2.85V

3.3V

Selectable Voltage

20kHz Frequency

8-Lead SOIC (M)

Pin Description

Pin No. (Version†) Pin Name Pin Function

1 SW Switch: NPN output switch transistor collector.
2 GND Power Ground: NPN output switch transistor emitter.

3 NC Not internally connected.
4 (-1) 5V 5V Feedback (Input): Fixed 5V feedback to internal resistive divider.
4 (-2) NC Not internally connected.
5 (-1) 3.3V 3.3V Feedback (Input): Fixed 3.3V feedback to internal resistive divider.
5 (-2) NC Not internally connected.
6 (-1) 2.85V 2.85V Feedback (Input): Fixed 2.85V feedback to internal resistive divider.
6 (-2) FB Feedback (Input): 0.22V feedback from external voltage divider network.

7 SYNC Synchronization (Input): Oscillator start timing. Oscillator synchronizes to

falling edge of sync signal.

8 IN Supply (Input): Positive supply voltage input.

†

Example: (-1) indicates the pin description is applicable to the MIC2570-1 only.

MIC2570-2

1

SW

NC
NC

2
3
4

GND

Adjustable Voltage

20kHz Frequency

8
7
6
5

IN
SYNC
FB
NC

4

1997 4-63

MIC2570 Micrel

Absolute Maximum Ratings

Supply Voltage (VIN) .....................................................18V

Switch Voltage (VSW)....................................................36V

Switch Current (ISW) .......................................................1A

Sync Voltage (V

) .................................... –0.3V to 15V

SYNC

Operating Ratings

Supply Voltage (VIN) .................................... +1.3V to +15V

Ambient Operating Temperature (TA) ........ –40°C to +85°C

Junction Temperature (TJ) ....................... –40°C to +125°C

SOIC Thermal Resistance (θJA)............................140°C/W

Storage Temperature (TA) ....................... –65°C to +150°C

SOIC Power Dissipation (PD)..................................400mW

Electrical Characteristics

VIN = 2.5V; TA = 25°C, bold indicates –40°C ≤ TA ≤ 85°C; unless noted
Parameter Condition Min Typ Max Units

Input Voltage Startup guaranteed, ISW = 100mA 1.3 15 V
Quiescent Current Output switch off 130 µA
Fixed Feedback Voltage MIC2570-1; V

MIC2570-1; V
MIC2570-1; V

2.85V pin

3.3V pin
5V pin

Reference Voltage MIC2570-2, [adj. voltage versions], I

Comparator Hysteresis MIC2570-2, [adj. voltage versions] 6 mV
Output Hysteresis MIC2570-1; V

MIC2570-1; V
MIC2570-1; V

Feedback Current MIC2570-1; V

MIC2570-1; V
MIC2570-1; V

2.85V pin

3.3V pin
5V pin

2.85V pin

3.3V pin
5V pin

MIC2570-2 [adj. voltage versions]; VFB = 0V 25 nA
Reference Line Regulation 1.5V ≤ VIN ≤ 15V 0.35 %/V
Switch Saturation Voltage V

= 1.3V, ISW = 300mA 250 mV

IN

= 1.5V, ISW = 800mA 450 mV

V

IN

VIN = 3.0V, ISW = 800mA 450 mV
Switch Leakage Current Output switch off, VSW = 36V 1 µA
Oscillator Frequency MIC2570-1, -2; ISW = 100mA 20 kHz
Maximum Output Voltage 36 V
Sync Threshold Voltage 0.7 V
Switch On-Time 35 µs
Currrent Limit 1.1 A
Duty Cycle VFB < V

General Note: Devices are ESD protected; however, handling precautions are recommended.
Note 1: Measured using comparator trip point.

, ISW = 100mA 67 %

REF

= V

= V

= V

= V

= V

= V

= V

, ISW = 100mA 2.85 V

OUT

, ISW = 100mA 3.30 V

OUT

, ISW = 100mA 5.00 V

OUT

= 100mA, Note 1 220 mV

SW

220 mV

= V

= V

, ISW = 100mA 65 mV

OUT

, ISW = 100mA 75 mV

OUT

, ISW = 100mA 120 mV

OUT

OUT

OUT

OUT

6 µA
6 µA
6 µA

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MIC2570 Micrel

0

0.5

1.0

1.5

2.0

0 0.2 0.4 0.6 0.8 1.0

SWITCH CURRENT (A)

SWITCH VOLTAGE (V)

0

0.5

1.0

1.5

2.0

0 0.2 0.4 0.6 0.8 1.0

SWITCH CURRENT (A)

SWITCH VOLTAGE (V)

50

75

100

125

150

175

200

-60 -30 0 30 60 90 120 150

QUIESCENT CURRENT (µA)

TEMPERATURE (°C)

0

25

50

75

100

125

150

175

200

0246810

QUIESCENT CURRENT (µA)

SUPPLY VOLTAGE (V)

0

25

50

75

100

125

150

-60 -30 0 30 60 90 120 150

OUTPUT HYSTERESIS (mV)

TEMPERATURE (°C)

Typical Characteristics

Switch Saturation Voltage

2.0
TA = –40°C

1.5

1.0

0.5

SWITCH CURRENT (A)

0

0 0.2 0.4 0.6 0.8 1.0

VIN= 3.0V

1.5V

SWITCH VOLTAGE (V)

2.5V

2.0V

Oscillator Frequency

vs. Temperature

30

VIN = 2.5V
I

= 100mA

SW

25

20

OSC. FREQUENCY (kHz)

15

-60 -30 0 30 60 90 120 150

TEMPERATURE (°C)

Switch Saturation Voltage

TA = 25°C

VIN = 3.0V

2.5V

2.0V

1.5V

Oscillator Duty Cycle

vs. Temperature

75

VIN = 2.5V
I

= 100mA

70

SW

65

60

DUTY CYCLE (%)

55

50

-60 -30 0 30 60 90 120 150

TEMPERATURE (°C)

Switch Saturation Voltage

TA = 85°C

VIN = 3.0V

1.5V

Quiescent Current

vs. Temperature

VIN = 2.5V

4

Feedback Current

10

8

6

4

2

FEEDBACK CURRENT (µA)

0

-60 -30 0 30 60 90 120 150

TEMPERATURE (°C)

Output Current Limit

1.75

1.50

1.25

1.00

1997 4-65

0.75

0.50

CURRENT LIMIT (A)

0.25
0

-60 -30 0 30 60 90 120 150

TEMPERATURE (°C)

vs. Temperature

VIN = 2.5V
MIC2570-1

vs. Temperature

Feedback Current

vs. Temperature

50

VIN = 2.5V

40

MIC2570-2

30

20

10

FEEDBACK CURRENT (nA)

0

-60 -30 0 30 60 90 120 150

TEMPERATURE (°C)

Switch Leakage Current

1000

100

0.1

0.01

SWITCH LEAKAGE CURRENT (nA)

vs. Temperature

10

1

-60 -30 0 30 60 90 120 150

TEMPERATURE (°C)

Quiescent Current

vs. Supply Voltage

–40°C

+25°C

+85°C

Output Hysteresis

vs. Temperature

5V

3.3V

2.85V

MIC2570 Micrel

Block Diagrams

V

V

BATT

BATT

IN

SYNC

MIC2570-1

Oscillator

0.22V

Reference

3.3V5V

2.85V GND

Driver

Selectable Voltage Version with External Components

IN

Oscillator

SYNC

MIC2570-2

SW

V

OUT

V

OUT

0.22V

Reference

Driver

FB

Adjustable Voltage Version with External Components

SW

GND

4-66 1997