MICREL MIC2571-1BMM, MIC2571-2BMM Datasheet

MIC2571 Micrel

IN

SW

GND

MIC2571-1

C2
47µF
16V

3.3V/8mA

C1*
47µF
16V

1V to1.5V

1 Cell

2.85V

3.3V
5V

2

4

5

6

1

7

8

L1

150µH

SYNC

D1

MBR0530

* Needed if battery is ≥ 4" from MIC2571
Circuit size < 0.3 in

2

excluding C1

MIC2571

Single-Cell Switching Regulator

Preliminary Information

General Description

Micrel’s MIC2571 is a micropower boost switching regulator
that operates from one alkaline, nickel-metal-hydride cell, or
lithium cell.

The MIC2571 accepts a positive input voltage between 0.9V
and 15V. Its typical no-load supply current is 120µA.

The MIC2571 is available in selectable fixed output or adjust­able output versions. The MIC2571-1 can be configured for

2.85V, 3.3V, or 5V by connecting one of three separate
feedback pins to the output. The MIC2571-2 can be config­ured for an output voltage ranging between its input voltage
and 36V, using an external resistor network.

The MIC2571 has a fixed switching frequency of 20kHz. An
external SYNC connection allows the switching frequency to
be synchronized to an external signal.

The MIC2571 requires only four components (diode, induc­tor, input capacitor and output capacitor) to implement a
boost regulator. A complete regulator can be constructed in
a 0.3 in2 area.

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

Features

• Operates from a single-cell supply

0.9V to 15V operation

• 120µA typical quiescent current

• Complete regulator fits 0.3 in2 area

• 2.85V/3.3V/5V selectable output voltage (MIC2571-1)

• Adjustable output up to 36V (MIC2571-2)

• 1A current limited pass element

• Frequency synchronization input

• 8-lead MSOP package

Applications

• Pagers

• LCD bias generator

• Battery-powered, hand-held instruments

• Palmtop computers

• Remote controls

• Detectors

• Battery Backup Supplies

T ypical Applications

C1*
47µF
16V

* Needed if battery is ≥ 4" from MIC2571
Circuit size < 0.3 in

Single-Cell to 5V DC-to-DC Converter

1V to1.5V

1 Cell

MIC2571-1

IN

SYNC

7

2

excluding C1

8

150µH

2.85V

GND

2

L1

SW

3.3V
5V

1
6
5
4

D1

MBR0530

C2
47µF
16V

5V/5mA

Single-Cell to 3.3V DC-to-DC Converter

4-76 1997

MIC2571 Micrel

Ordering Information

Part Number Temperature Range Voltage Frequency Package

MIC2571-1BMM –40°C to +85°C Selectable* 20kHz 8-lead MSOP
MIC2571-2BMM –40°C to +85°C Adjustable 20kHz 8-lead MSOP

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

Pin Configuration

MIC2571-1

SW

GND

NC

5V

1
2
3
4

8
7
6
5

IN
SYNC

2.85V

3.3V

Selectable Voltage

20kHz Frequency

8-Lead MSOP (MM)

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 MIC2571-1 only.

MIC2571-2

1

SW

2

GND

3

NC

4

NC

Adjustable Voltage

20kHz Frequency

8
7
6
5

IN
SYNC
FB
NC

4

1997 4-77

MIC2571 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) .................................... +0.9V to +15V

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

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

MSOP Thermal Resistance (θJA) ..........................240°C/W

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

MSOP Power Dissipation (PD)................................250mW

Electrical Characteristics

VIN = 1.5V; TA = 25°C, bold indicates –40°C ≤ TA ≤ 85°C; unless noted
Parameter Condition Min Typ Max Units

Input Voltage Startup guaranteed, I

Quiescent Current Output switch off 120 µA
Fixed Feedback Voltage MIC2571-1; V

MIC2571-1; V
MIC2571-1; V

2.85V pin

3.3V pin
5V pin

Reference Voltage MIC2571-2, [adj. voltage versions], I

Comparator Hysteresis MIC2571-2, [adj. voltage versions] 6 mV
Output Hysteresis MIC2571-1; V

MIC2571-1; V
MIC2571-1; V

Feedback Current MIC2571-1; V

MIC2571-1; V
MIC2571-1; V
MIC2571-2, [adj. voltage versions]; VFB = 0V 25 nA

2.85V pin

3.3V pin
5V pin

2.85V pin

3.3V pin
5V pin

Reference Line Regulation 1.0V ≤ VIN ≤ 12V 0.35 %/V
Switch Saturation Voltage V

= 1.0V, ISW = 200mA 200 mV

IN

V

= 1.2V, ISW = 600mA 400 mV

IN

VIN = 1.5V, ISW = 800mA 500 mV
Switch Leakage Current Output switch off, VSW = 36V 1 µA
Oscillator Frequency MIC2571-1, -2; ISW = 100mA 20 kHz
Maximum Output Voltage 36 V
Sync Threshold Voltage 0.7 V
Switch On Time 35 µ s
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

= 100mA 15 V

= V

= V

= V

= V

= V

= V

SW

= 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

, ISW = 100mA 65 mV

OUT

, ISW = 100mA 75 mV

OUT

, ISW = 100mA 120 mV

OUT

OUT

OUT

OUT

0.9 V

220 mV

4.5 µA

4.5 µA

4.5 µA

4-78 1997

MIC2571 Micrel

0

0.2

0.4

0.6

0.8

1.0

0 0.2 0.4 0.6 0.8 1.0

SWITCH CURRENT (A)

SWITCH VOLTAGE (V)

0

0.2

0.4

0.6

0.8

1.0

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

1.0
TA = –40°C

0.8

0.6

0.4

0.2

SWITCH CURRENT (A)

0

0 0.2 0.4 0.6 0.8 1.0

SWITCH VOLTAGE (V)

1.4V

1.3V

1.2V

1.1V

VIN = 1.0V

Oscillator Frequency

vs. Temperature

30

VIN = 1.5V
I

= 100mA

SW

25

20

OSC. FREQUENCY (kHz)

15

-60 -30 0 30 60 90 120 150

TEMPERATURE (°C)

Switch Saturation Voltage

1.4V

TA = 25°C

V

1.3V

1.2V

1.1V

1.0V

= 0.9V

Oscillator Duty Cycle

vs. Temperature

75

VIN = 1.5V
I

= 100mA

70

SW

65

60

DUTY CYCLE (%)

55

50

-60 -30 0 30 60 90 120 150

TEMPERATURE (°C)

Switch Saturation Voltage

1.3V

1.4V

TA = 85°C

1.2V

1.1V

1.0V
VIN = 0.9V

Quiescent Current

vs. Temperature

VIN = 1.5V

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 4-79

0.75

0.50

CURRENT LIMIT (A)

0.25
0

-60 -30 0 30 60 90 120 150

TEMPERATURE (°C)

vs. Temperature

VIN = 1.5V
MIC2571-1

vs. Temperature

Feedback Current

vs. Temperature

50

VIN = 2.5V

40

MIC2571-2

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

V

= 2.85V

OUT