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 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
a 0.6 in
2
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 in
2
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
•
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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
Typical Applications
L1
47µH
8
D1
MBRA140
5V/100mA
1
L1
50µH
C2
100µF
10V MBRA140
2
3
2.0V–3.1V
2 AA Cells
C1
100µF
10V
IN
MIC2570-1
SW
2.85V
3.3V
5V
1
6
5
4
U1
2.5V to 4.2V
1 Li Cell
C2
220µF
10V
C1
100µF
10V
IN
8
D1
L1
SW
1
4
V
OUT
3.3V/80mA
MIC2570
3.3V
SYNC GND
7
2
5
SYNC
7
GND
2
C3
330µF
6.3V
Two-Cell to 5V DC-to-DC Converter
Single-Cell Lithium to 3.3V/80mARegulator
4-62
1997
MICREL [ MICREL SEMICONDUCTOR ]
