MIC2570
Micrel, Inc.
MIC2570
Two-Cell Switching Regulator
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 ad-
justable 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, inductor,
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
•
•
•
•
•
•
•
•
•
•
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
2.0V–3.1V
2 AA Cells
1
L1
50µH
2
C2
100µF
10V
MBRA140
3
C1
100µF
10V
IN
MIC2570-1
S W
2.85V
3.3V
SYNC
7
1
6
5
4
C1
2.5V to 4.2V 100µF
1 Li Cell
10V
U1
8
IN
SW
D1
L1
V
OU T
3.3V/80mA
1
5
4
5V
GND
2
C2
220µF
10V
3.3V
S Y N C GND
7
2
MIC2570
C3
330µF
6.3V
Two-Cell to 5V DC-to-DC Converter
Single-Cell Lithium to 3.3V/80mARegulator
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
August 2007
1
MIC2570
MIC2570
Micrel, Inc.
Ordering Information
Part Number
Standard
MIC2570-1BM
MIC2570-2BM
Pb-Free
MIC2570-1YM
MIC2570-2YM
Temperature
Range
–40ºC to +85ºC
–40ºC to +85ºC
Voltage
Selectable*
Adjustable
Frequency
20kHz
20kHz
Package
8-pin SOIC
8-pin SOIC
* Externally selectable for 2.85V, 3.3V, or 5V
Pin Configuration
SW
1
GND
2
NC
3
5V
4
MIC2570-1
8
IN
7
SYNC
6
2.85V
5
3.3V
MIC2570-2
SW
1
8
7
6
5
IN
SYNC
FB
NC
GND
2
NC
3
NC
4
Selectable Voltage
20kHz Frequency
8-Lead SOIC (M)
Adjustable Voltage
20kHz Frequency
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 MIC2570-1 only.
MIC2570
2
August 2007
MIC2570
Micrel, Inc.
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
SOIC Power Dissipation (P
D
) .................................. 400mW
Operating Ratings
Supply Voltage (V
IN
) ..................................... +1.3V to +15V
Ambient Operating Temperature (T
A
) ......... –40°C to +85°C
Junction Temperature (T
J
) ........................ –40°C to +125°C
SOIC Thermal Resistance
(θ
JA
) ............................ 140°C/W
Electrical Characteristics
V
IN
= 2.5V; T
A
= 25°C,
bold
indicates –40°C ≤ T
A
≤ 85°C; unless noted
Parameter
Condition
Input Voltage
Quiescent Current
Fixed Feedback Voltage
Startup guaranteed, I
SW
= 100mA
Output switch off
MIC2570-1; V
2.85V pin
= V
OUT
, I
SW
= 100mA
MIC2570-1; V
3.3V pin
= V
OUT
, I
SW
= 100mA
MIC2570-1; V
5V pin
= V
OUT
, I
SW
= 100mA
MIC2570-2, [adj. voltage versions]
Min
1.3
130
2.7
3.14
4.75
208
2.85
3.30
5.00
220
6
65
75
120
6
6
6
25
0.35
250
450
450
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
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
MIC2570-2, [adj. voltage versions], I
SW
= 100mA,
Note 1
MIC2570-1; V
2.85V pin
= V
OUT
, I
SW
= 100mA
MIC2570-1; V
3.3V pin
= V
OUT
, I
SW
= 100mA
MIC2570-1; V
5V pin
= V
OUT
, I
SW
= 100mA
Feedback Current
Reference Line Regulation
Switch Saturation Voltage
MIC2570-1; V
2.85V pin
= V
OUT
MIC2570-1; V
3.3V pin
= V
OUT
MIC2570-1; V
5V pin
= V
OUT
MIC2570-2 [adj. voltage versions]; V
FB
= 0V
1.5V ≤ V
IN
≤ 15V
V
IN
= 1.3V, I
SW
= 300mA
V
IN
= 1.5V, I
SW
= 800mA
V
IN
= 3.0V, I
SW
= 800mA
Switch Leakage Current
Oscillator Frequency
Maximum Output Voltage
Sync Threshold Voltage
Switch On-Time
Currrent Limit
Duty Cycle
Note 1:
Output switch off, V
SW
= 36V
MIC2570-1, -2; I
SW
= 100mA
General Note:
Devices are ESD protected; however, handling precautions are recommended.
Measured using comparator trip point.
August 2007
3
MIC2570
MIC2570
Micrel, Inc.
Typical Characteristics
2.0
SWITCH CURRENT (A)
1.5
1.0
0.5
0
Switch Saturation Voltage
SWITCH CURRENT (A)
2.0
1.5
1.0
0.5
0
Switch Saturation Voltage
T
A
= 25°C
2.0
SWITCH CURRENT (A)
1.5
1.0
0.5
0
Switch Saturation Voltage
T
A
= 85°C
T
A
= –40°C
2.5V
V
IN
= 3.0V
V
IN
= 3.0V
1.5V
2.0V
V
IN
= 3.0V
2.5V
1.5V
1.5V
0
2.0V
0.2
0.4
0.6
0.8
SWITCH VOLTAGE (V)
1.0
0
0.2
0.4
0.6
0.8
SWITCH VOLTAGE (V)
1.0
0
0.2
0.4
0.6
0.8
SWITCH VOLTAGE (V)
1.0
30
OSC. FREQUENCY (kHz)
Oscillator Frequency
vs. Temperature
V
IN
= 2.5V
I
S W
= 100mA
75
70
65
60
55
Oscillator Duty Cycle
vs. Temperature
QUIESCENT CURRENT (µA)
25
DUTY CYCLE (%)
V
IN
= 2.5V
I
S W
= 100mA
200
175
150
125
100
75
Quiescent Current
vs. Temperature
V
IN
= 2.5V
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)
10
FEEDBACK CURRENT (µA)
8
6
4
2
Feedback Current
vs. Temperature
V
IN
= 2.5V
MIC2570-1
50
FEEDBACK CURRENT (nA)
40
30
20
10
Feedback Current
vs. Temperature
QUIESCENT CURRENT (µA)
200
175
150
125
100
75
50
25
0
0
Quiescent Current
vs. Supply Voltage
–40°C
V
IN
= 2.5V
MIC2570-2
+25°C
+85°C
0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
2
4
6
8
SUPPLY VOLTAGE (V)
10
SWITCH LEAKAGE CURRENT (nA)
1.75
1.50
CURRENT LIMIT (A)
1.25
1.00
0.75
0.50
0.25
Output Current Limit
vs. Temperature
1000
100
10
1
0.1
Switch Leakage Current
vs. Temperature
OUTPUT HYSTERESIS (mV)
150
125
100
75
50
25
Output Hysteresis
vs. Temperature
5V
3.3V
2.85V
0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
0.01
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
0
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
MIC2570
4
August 2007
MIC2570
Micrel, Inc.
Block Diagrams
V
BATT
V
OU T
IN
SYNC
MIC2570-1
Oscillator
0.22V
Reference
Driver
SW
5V
3.3V
2.85V
GND
Selectable Voltage Version with External Components
V
BATT
IN
V
OU T
SYNC
MIC2570-2
Oscillator
0.22V
Reference
Driver
SW
FB
GND
Adjustable Voltage Version with External Components
August 2007
5
MIC2570
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