MIC2571
Micrel
MIC2571
Single-Cell Switching Regulator
Final 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 adjust-
able 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 config-
ured 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, induc-
tor, input capacitor and output capacitor) to implement a
boost regulator. A complete regulator can be constructed in
a 0.3 in
2
area.
All versions are available in an 8-lead MSOP with an operat-
ing 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 in
2
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
Typical Applications
L1
150µH
8
D1
MBR0530
5V/5mA
8
L1
150µH
D1
MBR0530
3.3V/8mA
IN
SW
1V to1.5V
1 Cell
C1*
47µF
16V
2.85V
MIC2571-1
SYNC
7
1
6
5
4
IN
SW
1V to1.5V
1 Cell
C2
47µF
16V
C1*
47µF
16V
2.85V
MIC2571-1
SYNC
7
1
6
5
4
3.3V
5V
GND
2
3.3V
5V
GND
2
C2
47µF
16V
* Needed if battery is
≥
4" from MIC2571
Circuit size < 0.3 in
2
excluding C1
* Needed if battery is
≥
4" from MIC2571
Circuit size < 0.3 in
2
excluding C1
Single-Cell to 5V DC-to-DC Converter
Single-Cell to 3.3V DC-to-DC Converter
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
1997
1
MIC2571
MIC2571
Micrel
Ordering Information
Part Number
MIC2571-1BMM
MIC2571-2BMM
Temperature Range
–40°C to +85°C
–40°C to +85°C
Voltage
Selectable*
Adjustable
Frequency
20kHz
20kHz
Package
8-lead MSOP
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
SW
GND
NC
NC
1
2
3
4
MIC2571-2
8
7
6
5
IN
SYNC
FB
NC
Selectable Voltage
20kHz Frequency
Adjustable Voltage
20kHz Frequency
8-Lead MSOP (MM)
Pin Description
Pin No. (Version
†
)
1
2
3
4 (-1)
4 (-2)
5 (-1)
5 (-2)
6 (-1)
6 (-2)
7
8
†
Pin Name
SW
GND
NC
5V
NC
3.3V
NC
2.85V
FB
SYNC
IN
Pin Function
Switch: NPN output switch transistor collector.
Power Ground: NPN output switch transistor emitter.
Not internally connected.
5V Feedback (Input): Fixed 5V feedback to internal resistive divider.
Not internally connected.
3.3V Feedback (Input): Fixed 3.3V feedback to internal resistive divider.
Not internally connected.
2.85V Feedback (Input): Fixed 2.85V feedback to internal resistive divider.
Feedback (Input): 0.22V feedback from external voltage divider network.
Synchronization (Input): Oscillator start timing. Oscillator synchronizes to
falling edge of sync signal.
Supply (Input): Positive supply voltage input.
Example: (-1) indicates the pin description is applicable to the MIC2571-1 only.
MIC2571
2
1997
MIC2571
Micrel
Absolute Maximum Ratings
Supply Voltage (V
IN
) ..................................................... 18V
Switch Voltage (V
SW
) .................................................... 36V
Switch Current (I
SW
) ....................................................... 1A
Sync Voltage (V
SYNC
) .................................... –0.3V to 15V
Storage Temperature (T
A
) ....................... –65°C to +150°C
MSOP Power Dissipation (P
D
) ................................ 250mW
Operating Ratings
Supply Voltage (V
IN
) .................................... +0.9V to +15V
Ambient Operating Temperature (T
A
) ........ –40°C to +85°C
Junction Temperature (T
J
) ....................... –40°C to +125°C
MSOP Thermal Resistance
(θ
JA
) .......................... 240°C/W
Electrical Characteristics
V
IN
= 1.5V; T
A
= 25°C,
bold
indicates –40°C
≤
T
A
≤
85°C; unless noted
Parameter
Input Voltage
Quiescent Current
Fixed Feedback Voltage
Condition
Startup guaranteed, I
SW
= 100mA
Output switch off
MIC2571-1; V
2.85V pin
= V
OUT
, I
SW
= 100mA
MIC2571-1; V
3.3V pin
= V
OUT
, I
SW
= 100mA
MIC2571-1; V
5V pin
= V
OUT
, I
SW
= 100mA
MIC2571-2, [adj. voltage versions], I
SW
= 100mA,
Note 1
MIC2571-2, [adj. voltage versions]
MIC2571-1; V
2.85V pin
= V
OUT
, I
SW
= 100mA
MIC2571-1; V
3.3V pin
= V
OUT
, I
SW
= 100mA
MIC2571-1; V
5V pin
= V
OUT
, I
SW
= 100mA
MIC2571-1; V
2.85V pin
= V
OUT
MIC2571-1; V
3.3V pin
= V
OUT
MIC2571-1; V
5V pin
= V
OUT
MIC2571-2, [adj. voltage versions]; V
FB
= 0V
1.0V
≤
V
IN
≤
12V
V
IN
= 1.0V, I
SW
= 200mA
V
IN
= 1.2V, I
SW
= 600mA
V
IN
= 1.5V, I
SW
= 800mA
Output switch off, V
SW
= 36V
MIC2571-1, -2; I
SW
= 100mA
2.7
3.14
4.75
208
Min
0.9
120
2.85
3.30
5.00
220
6
65
75
120
4.5
4.5
4.5
25
0.35
200
400
500
1
20
36
0.7
35
1.1
V
FB
< V
REF
, I
SW
= 100mA
67
3.0
3.47
5.25
232
Typ
Max
15
Units
V
V
µA
V
V
V
mV
mV
mV
mV
mV
µA
µA
µA
nA
%/V
mV
mV
mV
µA
kHz
V
V
µs
A
%
Reference Voltage
Comparator Hysteresis
Output Hysteresis
Feedback Current
Reference Line Regulation
Switch Saturation Voltage
Switch Leakage Current
Oscillator Frequency
Maximum Output Voltage
Sync Threshold Voltage
Switch On Time
Currrent Limit
Duty Cycle
Note 1:
General Note:
Devices are ESD protected; however, handling precautions are recommended.
Measured using comparator trip point.
1997
3
MIC2571
MIC2571
Micrel
Typical Characteristics
Switch Saturation Voltage
1.0
T
A
= –40°C
SWITCH CURRENT (A)
SWITCH CURRENT (A)
0.8
0.6
0.4
0.2
V
IN
= 1.0V
0
0
0.2
0.4
0.6
0.8
SWITCH VOLTAGE (V)
1.0
0
1.4V
1.3V
1.2V
1.1V
0.8
1.0
Switch Saturation Voltage
1.0
1.4V
T
A
= 25°C
0.6
0.4
0.2
1.1V
1.0V
V
IN
= 0.9V
0
0.2
0.4
0.6
0.8
SWITCH VOLTAGE (V)
1.0
1.3V
SWITCH CURRENT (A)
1.2V
0.8
0.6
Switch Saturation Voltage
1.4V
T
A
= 85°C
1.3V
1.2V
1.1V
1.0V
0.4
0.2
0
V
IN
= 0.9V
0
0.2
0.4
0.6
0.8
SWITCH VOLTAGE (V)
1.0
Oscillator Frequency
vs. Temperature
30
OSC. FREQUENCY (kHz)
V
IN
= 1.5V
I
SW
= 100mA
25
75
Oscillator Duty Cycle
vs. Temperature
200
QUIESCENT CURRENT (µA)
V
IN
= 1.5V
I
SW
= 100mA
175
150
125
100
75
Quiescent Current
vs. Temperature
V
IN
= 1.5V
DUTY CYCLE (%)
70
65
60
55
20
15
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
50
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
50
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
Feedback Current
vs. Temperature
10
FEEDBACK CURRENT (µA)
FEEDBACK CURRENT (nA)
8
6
4
2
0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
V
IN
= 1.5V
MIC2571-1
50
40
30
20
10
Feedback Current
vs. Temperature
200
V
IN
= 2.5V
MIC2571-2
QUIESCENT CURRENT (µA)
175
150
125
100
75
50
25
0
0
Quiescent Current
vs. Supply Voltage
–40°C
+25°C
+85°C
0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
2
4
6
8
SUPPLY VOLTAGE (V)
10
1.75
1.50
CURRENT LIMIT (A)
1.25
1.00
0.75
0.50
0.25
0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
SWITCH LEAKAGE CURRENT (nA)
Output Current Limit
vs. Temperature
Switch Leakage Current
vs. Temperature
1000
OUTPUT HYSTERESIS (mV)
100
10
1
0.1
0.01
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
150
125
100
Output Hysteresis
vs. Temperature
5V
3.3V
75
50
25
0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
V
OUT
= 2.85V
MIC2571
4
1997
MIC2571
Micrel
Block Diagrams
V
BATT
IN
SYNC
MIC2571-1
Oscillator
0.22V
Reference
V
OUT
Driver
SW
5V
3.3V
2.85V
GND
Selectable Voltage Version with External Components
V
BATT
IN
SYNC
MIC2571-2
Oscillator
0.22V
Reference
V
OUT
Driver
SW
FB
GND
Adjustable Voltage Version with External Components
1997
5
MIC2571
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