1997
1
MIC2570
MIC2570
Micrel
MIC2570
Two-Cell Switching Regulator
Final 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 130
A.
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
.
Typical Applications
Features
Operates from a two-cell supply
1.3V to 15V operation
130
A 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
Two-Cell to 5V DC-to-DC Converter
IN
SW
GND
MIC2570-1
C2
220F
10V
5V/100mA
C1
100F
10V
2.0V3.1V
2 AA Cells
2.85V
3.3V
5V
2
4
5
6
1
7
8
L1
47H
SYNC
D1
MBRA140
Single-Cell Lithium to 3.3V/80mARegulator
GND
3.3V
SW
MIC2570
SYNC
7
5
1
2
8
IN
C3
330F
6.3V
V
OUT
3.3V/80mA
2.5V to 4.2V
1 Li Cell
C1
100F
10V
D1
MBRA140
L1
50H
L1
C2
100F
10V
U1
1
2
3
4
Micrel, Inc. 1849 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 http://www.micrel.com
MIC2570
Micrel
MIC2570
2
1997
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
1
2
3
4
8
7
6
5
SW
GND
NC
5V
IN
SYNC
2.85V
3.3V
MIC2570-1
Selectable Voltage
20kHz Frequency
1
2
3
4
8
7
6
5
IN
SYNC
FB
NC
SW
GND
NC
NC
MIC2570-2
Adjustable 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.
1997
3
MIC2570
MIC2570
Micrel
Electrical Characteristics
V
IN
= 2.5V; T
A
= 25
C, bold indicates 40
C
T
A
85
C; unless noted
Parameter
Condition
Min
Typ
Max
Units
Input Voltage
Startup guaranteed, I
SW
= 100mA
1.3
15
V
Quiescent Current
Output switch off
130
A
Fixed Feedback Voltage
MIC2570-1; V
2.85V pin
= V
OUT
, I
SW
= 100mA
2.85
V
MIC2570-1; V
3.3V pin
= V
OUT
, I
SW
= 100mA
3.30
V
MIC2570-1; V
5V pin
= V
OUT
, I
SW
= 100mA
5.00
V
Reference Voltage
MIC2570-2, [adj. voltage versions], I
SW
= 100mA, Note 1
220
mV
220
mV
Comparator Hysteresis
MIC2570-2, [adj. voltage versions]
6
mV
Output Hysteresis
MIC2570-1; V
2.85V pin
= V
OUT
, I
SW
= 100mA
65
mV
MIC2570-1; V
3.3V pin
= V
OUT
, I
SW
= 100mA
75
mV
MIC2570-1; V
5V pin
= V
OUT
, I
SW
= 100mA
120
mV
Feedback Current
MIC2570-1; V
2.85V pin
= V
OUT
6
A
MIC2570-1; V
3.3V pin
= V
OUT
6
A
MIC2570-1; V
5V pin
= V
OUT
6
A
MIC2570-2 [adj. voltage versions]; V
FB
= 0V
25
nA
Reference Line Regulation
1.5V
V
IN
15V
0.35
%/V
Switch Saturation Voltage
V
IN
= 1.3V, I
SW
= 300mA
250
mV
V
IN
= 1.5V, I
SW
= 800mA
450
mV
V
IN
= 3.0V, I
SW
= 800mA
450
mV
Switch Leakage Current
Output switch off, V
SW
= 36V
1
A
Oscillator Frequency
MIC2570-1, -2; I
SW
= 100mA
20
kHz
Maximum Output Voltage
36
V
Sync Threshold Voltage
0.7
V
Switch On-Time
35
s
Currrent Limit
1.1
A
Duty Cycle
V
FB
< V
REF
, I
SW
= 100mA
67
%
General Note: Devices are ESD protected; however, handling precautions are recommended.
Note 1:
Measured using comparator trip point.
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
(
JA
) ............................ 140
C/W
MIC2570
Micrel
MIC2570
4
1997
Typical Characteristics
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)
Switch Saturation Voltage
T
A
= 40
C
V
IN
= 3.0V
2.5V
2.0V
1.5V
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)
Switch Saturation Voltage
T
A
= 25
C
V
IN
= 3.0V
2.0V
2.5V
1.5V
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)
Switch Saturation Voltage
T
A
= 85
C
1.5V
V
IN
= 3.0V
15
20
25
30
-60 -30
0
30
60
90 120 150
OSC. FREQUENCY (kHz)
TEMPERATURE (
C)
Oscillator Frequency
vs. Temperature
V
IN
= 2.5V
I
SW
= 100mA
50
55
60
65
70
75
-60 -30
0
30
60
90 120 150
DUTY CYCLE (%)
TEMPERATURE (
C)
Oscillator Duty Cycle
vs. Temperature
V
IN
= 2.5V
I
SW
= 100mA
50
75
100
125
150
175
200
-60 -30
0
30
60
90 120 150
QUIESCENT CURRENT (
A)
TEMPERATURE (
C)
Quiescent Current
vs. Temperature
V
IN
= 2.5V
0
2
4
6
8
10
-60 -30
0
30
60
90 120 150
FEEDBACK CURRENT (
A)
TEMPERATURE (
C)
Feedback Current
vs. Temperature
V
IN
= 2.5V
MIC2570-1
0
10
20
30
40
50
-60 -30
0
30
60
90 120 150
FEEDBACK CURRENT (nA)
TEMPERATURE (
C)
Feedback Current
vs. Temperature
V
IN
= 2.5V
MIC2570-2
0
25
50
75
100
125
150
175
200
0
2
4
6
8
10
QUIESCENT CURRENT (
A)
SUPPLY VOLTAGE (V)
Quiescent Current
vs. Supply Voltage
40
C
+85
C
+25
C
0
0.25
0.50
0.75
1.00
1.25
1.50
1.75
-60 -30
0
30
60
90 120 150
CURRENT LIMIT (A)
TEMPERATURE (
C)
Output Current Limit
vs. Temperature
0.01
0.1
1
10
100
1000
-60 -30
0
30
60
90 120 150
SWITCH LEAKAGE CURRENT (nA)
TEMPERATURE (
C)
Switch Leakage Current
vs. Temperature
0
25
50
75
100
125
150
-60 -30
0
30
60
90 120 150
OUTPUT HYSTERESIS (mV)
TEMPERATURE (
C)
Output Hysteresis
vs. Temperature
2.85V
3.3V
5V
1997
5
MIC2570
MIC2570
Micrel
Block Diagrams
Oscillator
0.22V
Reference
Driver
IN
V
BATT
2.85V
GND
SW
SYNC
3.3V
5V
V
OUT
MIC2570-1
Selectable Voltage Version with External Components
Oscillator
0.22V
Reference
Driver
IN
V
BATT
GND
SW
SYNC
MIC2570-2
V
OUT
FB
Adjustable Voltage Version with External Components
MIC2570
Micrel
MIC2570
6
1997
Functional Description
The MIC2570 switch-mode power supply (SMPS) is a gated
oscillator architecture designed to operate from an input
voltage as low as 1.3V and provide a high-efficiency fixed or
adjustable regulated output voltage. One advantage of this
architecture is that the output switch is disabled whenever the
output voltage is above the feedback comparator threshold
thereby greatly reducing quiescent current and improving
efficiency, especially at low output currents.
Refer to the Block Diagrams for the following discription of
typical gated oscillator boost regulator function.
The bandgap reference provides a constant 0.22V over a
wide range of input voltage and junction temperature. The
comparator senses the output voltage through an internal or
external resistor divider and compares it to the bandgap
reference voltage.
When the voltage at the inverting input of the comparator is
below 0.22V, the comparator output is high and the output of
the oscillator is allowed to pass through the AND gate to the
output driver and output switch. The output switch then turns
on and off storing energy in the inductor. When the output
switch is on (low) energy is stored in the inductor; when the
switch is off (high) the stored energy is dumped into the output
capacitor which causes the output voltage to rise.
When the output voltage is high enough to cause the com-
parator output to be low (inverting input voltage is above
0.22V) the AND gate is disabled and the output switch
remains off (high). The output switch remains disabled until
the output voltage falls low enough to cause the comparator
output to go high.
There is about 6mV of hysteresis built into the comparator to
prevent jitter about the switch point. Due to the gain of the
feedback resistor divider the voltage at V
OUT
experiences
about 120mV of hysteresis for a 5V output.
Appications Information
Oscillator Duty Cycle and Frequency
The oscillator duty cycle is set to 67% which is optimized to
provide maximum load current for output voltages approxi-
mately 3
larger than the input voltage. Other output voltages
are also easily generated but at a small cost in efficiency. The
fixed oscillator frequency (options -1 and -2) is set to 20kHz.
Output Waveforms
The voltage waveform seen at the collector of the output
switch (SW pin) is either a continuous value equal to V
IN
or a
switching waveform running at a frequency and duty cycle set
by the oscillator. The continuous voltage equal to V
IN
happens when the voltage at the output (V
OUT
) is high
enough to cause the comparator to disable the AND gate. In
this state the output switch is off and no switching of the
inductor occurs. When V
OUT
drops low enough to cause the
comparator output to change to the high state the output
switch is driven by the oscillator. See Figure 1 for typical
voltage waveforms in a boost application.
5V
0V
5V
0mA
I
PEAK
V
IN
Supply
Voltage
Inductor
Current
Output
Voltage
Time
Figure 1. Typical Boost Regulator Waveforms
Synchronization
The SYNC pin is used to synchronize the MIC2570 to an
external oscillator or clock signal. This can reduce system
noise by correlating switching noise with a known system
frequency. When not in use, the SYNC pin should be
grounded to prevent spurious circuit operation. A falling edge
at the SYNC input triggers a one-shot pulse which resets the
oscillator. It is possible to use the SYNC pin to generate
oscillator duty cycles from approximately 20% up to the
nominal duty cycle.
Current Limit
Current limit for the MIC2570 is internally set with a resistor.
It functions by modifying the oscillator duty cycle and fre-
quency. When current exceeds 1.2A, the duty cycle is
reduced (switch on-time is reduced, off-time is unaffected)
and the corresponding frequency is increased. In this way
less time is available for the inductor current to build up while
maintaining the same discharge time. The onset of current
limit is soft rather than abrupt but sufficient to protect the
inductor and output switch from damage. Certain combina-
tions of input voltage, output voltage and load current can
cause the inductor to go into a continuous mode of operation.
This is what happens when the inductor current can not fall to
zero and occurs when:
duty cycle
V
+ V
V
V
+ V
V
OUT
DIODE
IN
OUT
DIODE
SAT
Time
Inductor Current
Current "ratchet"
without current limit
Current Limit
Threshold
Continuous
Current
Discontinuous
Current
Figure 2. Current Limit Behavior
1997
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MIC2570
MIC2570
Micrel
Figure 2 shows an example of inductor current in the continu-
ous mode with its associated change in oscillator frequency
and duty cycle. This situation is most likely to occur with
relatively small inductor values, large input voltage variations
and output voltages which are less than ~3
the input voltage.
Selection of an inductor with a saturation threshold above
1.2A will insure that the system can withstand these condi-
tions.
Inductors, Capacitors and Diodes
The importance of choosing correct inductors, capacitors and
diodes can not be ignored. Poor choices for these compo-
nents can cause problems as severe as circuit failure or as
subtle as poorer than expected efficiency.
a.
b.
c.
Inductor Current
Time
Figure 3. Inductor Current: a. Normal,
b. Saturating, and c. Excessive ESR
Inductors
Inductors must be selected such that they do not saturate
under maximum current conditions. When an inductor satu-
rates, its effective inductance drops rapidly and the current
can suddenly jump to very high and destructive values.
Figure 3 compares inductors with currents that are correct
and unacceptable due to core saturation. The inductors have
the same nominal inductance but Figure 3b has a lower
saturation threshold. Another consideration in the selection
of inductors is the radiated energy. In general, toroids have
the best radiation characteristics while bobbins have the
worst. Some bobbins have caps or enclosures which signifi-
cantly reduce stray radiation.
The last electrical characteristic of the inductor that must be
considered is ESR (equivalent series resistance). Figure 3c
shows the current waveform when ESR is excessive. The
normal symptom of excessive ESR is reduced power transfer
efficiency.
Capacitors
It is important to select high-quality, low ESR, filter capacitors
for the output of the regulator circuit. High ESR in the output
capacitor causes excessive ripple due to the voltage drop
across the ESR. A triangular current pulse with a peak of
500mA into a 200m
ESR can cause 100mV of ripple at the
output due the capacitor only. Acceptable values of ESR are
typically in the 50m
range. Inexpensive aluminum electro-
lytic capacitors usually are the worst choice while tantalum
capacitors are typically better. Figure 4 demonstrates the
effect of capacitor ESR on output ripple voltage.
4.75
5.00
5.25
0
500
1000
1500
OUTPUT VOLTAGE (V)
TIME (
s)
Figure 4. Output Ripple
Output Diode
Finally, the output diode must be selected to have adequate
reverse breakdown voltage and low forward voltage at the
application current. Schottky diodes typically meet these
requirements.
Standard silicon diodes have forward voltages which are too
large except in extremely low power applications. They can
also be very slow, especially those suited to power rectifica-
tion such as the 1N400x series, which affects efficiency.
Inductor Behavior
The inductor is an energy storage and transfer device. Its
behavior (neglecting series resistance) is described by the
following equation:
I =
V
L
t
where:
V = inductor voltage (V)
L = inductor value (H)
t = time (s)
I = inductor current (A)
If a voltage is applied across an inductor (initial current is
zero) for a known time, the current flowing through the
inductor is a linear ramp starting at zero, reaching a maximum
value at the end of the period. When the output switch is on,
the voltage across the inductor is:
V = V V
1
IN
SAT
When the output switch turns off, the voltage across the
inductor changes sign and flies high in an attempt to maintain
a constant current. The inductor voltage will eventually be
clamped to a diode drop above V
OUT
. Therefore, when the
output switch is off, the voltage across the inductor is:
V = V
+ V
V
2
OUT
DIODE
IN
For normal operation the inductor current is a triangular
waveform which returns to zero current (discontinuous mode)
MIC2570
Micrel
MIC2570
8
1997
at each cycle. At the threshold between continuous and
discontinuous operation we can use the fact that I
1
= I
2
to get:
V
t = V
t
1
1
2
2
V
V
=
t
t
1
2
2
1
This relationship is useful for finding the desired oscillator
duty cycle based on input and output voltages. Since input
voltages typically vary widely over the life of the battery, care
must be taken to consider the worst case voltage for each
parameter. For example, the worst case for t
1
is when V
IN
is
at its minimum value and the worst case for t
2
is when V
IN
is
at its maximum value (assuming that V
OUT
, V
DIODE
and V
SAT
do not change much).
To select an inductor for a particular application, the worst
case input and output conditions must be determined. Based
on the worst case output current we can estimate efficiency
and therefore the required input current. Remember that this
is
power conversion, so the worst case average input current
will occur at maximum output current and minimum input
voltage.
Average I
=
V
I
V
Efficiency
IN(max)
OUT
OUT(max)
IN(min)
Referring to Figure 1, it can be seen the peak input current will
be twice the average input current. Rearranging the inductor
equation to solve for L:
L =
V
I
t
1
L =
V
2
Average I
t
IN(min)
IN(max)
1
where t =
duty cycle
f
1
OSC
To illustrate the use of these equations a design example will
be given:
Assume:
MIC2570-1 (fixed oscillator)
V
OUT
= 5V
I
OUT(max)
=50mA
V
IN(min)
= 1.8V
efficiency = 75%.
Average I
=
5V
50mA
1.8V
0.75
= 185.2mA
IN(max)
L =
1.8V
0.7
2
185.2mA
20kHz
L = 170
H
Use the next lowest standard value of inductor and verify that
it does not saturate at a current below about 400mA
(< 2
185.2mA).
1997
9
MIC2570
MIC2570
Micrel
Application Examples
GND
5V
SW
MIC2570
SYNC
U1 Micrel
MIC2570-1BM
C1 AVX
TPSD107M010R0100 Tantalum, ESR = 0.1
C2 AVX
TPSE227M010R0100 Tantalum, ESR = 0.1
D1 Motorola
MBRA140T3
L1
Coilcraft
DO3316P-473, DCR = 0.12
7
4
1
2
8
IN
C2
220F
10V
V
OUT
5V/100mA
2.0V to 3.1V
2 Cells
C1
100F
10V
D1
MBRA140
L1
47H
U1
Example 1. 5V/100mA Regulator
GND
3.3V
SW
MIC2570
SYNC
U1 Micrel
MIC2570-1BM
C1 AVX
TPSD107M010R0100 Tantalum, ESR = 0.1
C2 AVX
TPSE337M006R0100 Tantalum, ESR = 0.1
D1 Motorola
MBRA140T3
L1
Coilcraft
DO3316P-473, DCR = 0.12
7
5
1
2
8
IN
C2
330F
6.3V
V
OUT
3.3V/150mA
2.0V to 3.1V
2 Cells
C1
100F
10V
D1
MBRA140
L1
47H
U1
Example 2. 3.3V/150mA Regulator
GND
FB
SW
MIC2570
SYNC
U1 Micrel
MIC2570-2BM
C1 AVX
TPSD107M010R0100 Tantalum, ESR = 0.11
C2 AVX
TPSE336M025R0300 Tantalum, ESR = 0.3
D1 Motorola
MBRA140T3
L1
Coilcraft
DO3316P-473, DCR = 0.12
7
6
1
2
8
IN
C2
33F
25V
V
OUT
12V/40mA
2.0V to 3.1V
2 Cells
C1
100F
10V
D1
MBRA140
L1
47H
R2
1M
1%
R1
18.7k
1%
V
OUT
= 0.22V (1+R2/R1)
U1
Example 3. 12V/40mA Regulator
GND
3.3V
SW
MIC2570
SYNC
U1 Micrel
MIC2570-1BM
C1 AVX
TPSD107M010R0100 Tantalum, ESR = 0.1
C2 AVX
TPSD107M010R0100 Tantalum, ESR = 0.1
C3 AVX
TPSE337M006R0100 Tantalum, ESR = 0.1
D1 Motorola
MBRA140T3
L1
Coiltronics CTX50-4P DCR = 0.097
7
5
1
2
8
IN
C3
330F
6.3V
V
OUT
3.3V/80mA
2.5V to 4.2V
1 Li Cell
C1
100F
10V
D1
MBRA140
L1
50H
L1
C2
100F
10V
U1
1
2
3
4
Example 4. Single Cell Lithium
to 3.3V/80mA Regulator
GND
FB
SW
MIC2570
SYNC
U1 Micrel
MIC2570-2BM
U2 Micrel
MIC5203-5.0BM4
C1 AVX
TPSD107M010R0100 Tantalum ESR = 0.1
C2 AVX
TPSE227M010R0300 Tantalum ESR = 0.1
C3 Sprague
293D105X0016A2W Tantalum
D1 Motorola
MBRA140T3
L1
Coilcraft
DO3316P-473 DCR = 0.12
7
6
1
2
8
IN
C1
100F
10V
D1
L1
47H
2.0V to 3.1V
2 Cells
V
OUT
= 0.22V (1+R2/R1)
U1
MBRA140
C2
220F
10V
MIC5203
IN
EN
GND
OUT
V
OUT
5V/80mA
C3
1F
16V
1
2
3
4
R1
20k
1%
R2
523k
1%
6V
U2
Example 5. Low-Noise 5V/80mA Regulator
MIC2570
Micrel
MIC2570
10
1997
GND
FB
SW
MIC2570
SYNC
U1 Micrel
MIC2570-2BM
U2 Micrel
MIC5203-3.3BM4
C1 AVX
TPSD107M010R0100 Tantalum ESR = 0.1
C2 AVX
TPSE227M010R0100 Tantalum ESR = 0.1
C3 Sprague
293D105X0016A2W Tantalum
D1 Motorola
MBRA140T3
L1
Coilcraft
DO3316P-473 DCR = 0.12
7
6
1
2
8
IN
C1
100F
10V
D1
L1
47H
2.0V to 3.1V
2 Cells
V
OUT
= 0.22V (1+R2/R1)
U1
MBRA140
C2
220F
10V
MIC5203
IN
EN
GND
OUT
V
OUT
3.3V/80mA
C3
1F
16V
1
2
3
4
R1
20k
1%
R2
374k
1%
U2
4.3V
Example 6. Low-Noise 3.3V/80mA Regulator
GND
5V
SW
MIC2570
SYNC
U1 Micrel
MIC2570-1BM
C1 AVX
TPSD107M010R0100 Tantalum, ESR = 0.1
C2 AVX
TPSE227M010R0100 Tantalum, ESR = 0.1
C3 AVX
TPSE227M010R0100 Tantalum, ESR = 0.1
C4 AVX
TPSE227M010R0100 Tantalum, ESR = 0.1
D1 Motorola
MBRA140T3
D2 Motorola
MBRA140T3
D3 Motorola
MBRA140T3
L1
Coilcraft
DO3316P-473, DCR = 1.2
7
4
1
2
8
IN
C2
220F
10V
+V
OUT
5V/50mA
2.0V to 3.1V
2 Cells
C1
100F
16V
D1
MBRA140
L1
47H
C3
220F
10V
D2
MBRA140
D3
MBRA140
C4
220F
10V
V
OUT
4.5V to 5V/50mA
I
OUT
+I
OUT
U1
Example 7.
5V/50mA Regulator
GND
FB
SW
MIC2570
SYNC
U1 Micrel
MIC2570-2BM
C1 AVX
TPSD107M010R0100, Tantalum ESR = 0.1
C2 AVX
TPSE226M035R0300, Tantalum ESR = 0.3
C3 AVX
TPSE226M035R0300, Tantalum ESR = 0.3
D1 Motorola
MBRA140T3
D2 Motorola
MBRA140T3
L1
Coilcraft
DO3316P-473, DCR = 0.12
7
6
1
2
8
IN
C3
0.1F
C1
100F
10V
D3
1N4148
L1
47H
R2
549k
1%
R1
4.99k
1%
2.0V to 3.1V
2 Cells
R3
220k
C2
22F
35V
V
OUT
24V/20mA
D2
MBRA140
D1
MBRA140
C1
22F
35V
V
OUT
= 0.22V (1+R2/R1) + 0.6V
U1
Example 8. 24V/20mA Regulator
1997
11
MIC2570
MIC2570
Micrel
GND
FB
SW
MIC2570
SYNC
U1 Micrel
MIC2570-2BM
C1 Sanyo
16MV330GX Electrolytic ESR = 0.1
C2 Sanyo
35MV68GX Electrolytic ESR = 0.22
C3 Sanyo
35MV68GX Electrolytic ESR = 0.22
C4 Sanyo
63MV826X Electrolytic ESR = 0.34
D1 Motorola
1N5819
D2 Motorola
1N5819
D3 Motorola
1N5819
L1
Sumida
RCH106-470k DCR = 0.16
7
6
1
2
8
IN
C1
330F
16V
D1
L1
47H
2.0V to 3.1V
2 Cell
1N5819
D2
1N5819
D3
1N5819
C3
68F
35V
R2
2.2M
1%
R1
10k
1%
C4
82F
63V
V
OUT
50V/10mA
C2
68F, 35V
U1
V
OUT
= 0.22
1+R2/R1)
Example 9. Voltage Doubler
GND
FB
SW
MIC2570
SYNC
U1 Micrel
MIC2570-2BM
C1 AVX
TPSD107M010R0100 Tantalum ESR = 0.1
C2 AVX
TPSE227M010R0100 Tantalum ESR = 0.1
D1 Motorola
MBRA140T3
L1
Coilcraft
DO3316P-473 DCR = 0.12
7
6
1
2
8
IN
C2
220F
10V
2.0V to 3.1V
2 Cell
C1
100F
10V
D1
MBRA140
L1
47H
R1
11k
1%
I = 0.22V/R1
D2
LED
X5 I
LED
U1
Example 10. Constant-Current LED Supply
Enable
Shutdown
GND
FB
SW
MIC2570
SYNC
U1 Micrel
MIC2570-2BM
C1 AVX
TPSD107M010R0100 Tantalum ESR = 0.1
C2 AVX
TPSE227M010R0100 Tantalum ESR = 0.1
D1 Motorola
MBRA140T3
L1
Coilcraft
DO3316P-473 DCR = 0.12
7
6
1
2
8
IN
C1
100F
10V
D1
L1
47H
2.0V to 3.1V
2 Cell
V
OUT
= 0.22V (1+R2/R1)
MBRA140
C2
220F
10V
R1
20k
1%
R2
434k
1%
D2
1N4148
74C04
V
OUT
5V/100mA
U1
R3
100k
Example 11. 5V/100mA Regulator with Shutdown
MIC2570
Micrel
MIC2570
12
1997
GND
FB
SW
MIC2570
SYNC
U1 Micrel
MIC2570-2BM
C1 AVX
TPSD107M010R0100 Tantalum ESR = 0.1
C2 AVX
TPSE227M010R0100 Tantalum ESR = 0.1
C3 AVX
TPSE227M010R0100 Tantalum ESR = 0.1
D1 Motorola
MBRA140T3
L1
Coilcraft
DO3316P-473 DCR = 0.12
Q1 Zetex
ZTX7888
7
6
1
2
8
IN
C1
100F
10V
D1
L1
47H
2.0V to 3.1V
2 Cell
V
OUT
= 0.22V (1+R2/R1)
MBRA140
C3
220F
10V
R1
20k
1%
R2
434k
1%
D2
1N4148
74C04
V
OUT
5V/100mA
C2
220F
10V
R1
510
Enable
Shutdown
Q1
ZTX7888
U1
R3
100k
Example 12. 5V/100mA Regulator with Shutdown and Output Disconnect
GND
5V
SW
MIC2570
SYNC
U1 Micrel
MIC2570-1BM
C1 AVX
TPSD107M010R0100 Tantalum ESR = 0.1
C2 AVX
TPSE227M010R0100 Tantalum ESR = 0.1
D1 Motorola
MBRA140T3
D2 Motorola
MBRS130L
L1
Coilcraft
DO3316P-473 DCR = 0.12
7
4
1
2
8
IN
C2
220F
10V
V
OUT
5V/70mA
2.0V to 3.1V
2 Cell
C1
100F
10V
D1
MBRA140
L1
47H
D2
MBRS130L
U1
Example 13. Reversed-Battery Protected Regulator
GND
5V
SW
MIC2570
SYNC
U1 Micrel
MIC2570-1BM
C1 AVX
TPSD107M010R0100 Tantalum ESR = 0.1
C2 AVX
TPSE227M010R0100 Tantalum ESR = 0.1
D1 Motorola
MBRA140T3
D2 Motorola
MBRS130LT3
D3 Motorola
MBRS130LT3
L1
Coilcraft
DO3316P-473 DCR = 0.12
Q1 Siliconix
Si9434 PMOS
7
4
1
2
8
IN
C2
220F
10V
V
OUT
5V/100mA
C1
100F
10V
D1
MBRA140
L1
47H
D3
1N4148
D2
1N4148
C3
0.1F
2.0V to 3.1V
2 Cell
R1
100k
C4
0.1F
Q1
Si9434
U1
body diode
Example 14. Improved Reversed-Battery Protected Regulator
1997
13
MIC2570
MIC2570
Micrel
Component Cross Reference
Capacitors
AVX
Sprague
Sanyo
Sanyo
Surface Mount
Surface Mount
Through Hole
Through Hole
(Tantalum)
(Tantalum)
(OS-CON)
(AL Electrolytic)
330
F/6.3V
TPSE337M006R0100
593D337X06R3E2W
10SA220M
16MV330GX (330
F/16V)
220
F/10V
TPSE227M010R0100
593D227X0010E2W
10SA220M
16MV330GX (330
F/16V)
100
F/10V
TPSD107M010R0100
593D107X0010D2W
10SA100M
16MV330GX (330
F/16V)
33
F/25V
TPSE336M025R0300
593D336X0025E2W
35MV68GX (68
F/35V)
22
F/35V
TPSE226M035R0300
593D226X0035E2W
35MV68GX (68
F/35V)
Diodes
Motorola
GI
IR
Motorola
Surface Mount
Surface Mount
Surface Mount
Through Hole
(Schottky)
(Schottky)
(Schottky)
(Schottky)
1A/40V
MBRA140T3
SS14
10MQ40
1N5819
1A/20V
1N5817
Inductors
Coilcraft
Coiltronics
Sumida
Sumida
Surface Mount
Surface Mount
Surface Mount
Through Hole
(Button Cores)
(Torriod)
(Button Cores)
(Button Cores)
22
H
DO3308P-223
47
H
DO3316P-473
CD75-470LC
RCH-106-470k
50
H
CTX50-4P
Suggested Manufacturers List
Inductors
Capacitors
Diodes
Transistors
Coilcraft
AVX Corp.
General Instruments (GI)
Siliconix
1102 Silver Lake Rd.
801 17th Ave. South
10 Melville Park Rd.
2201 Laurelwood Rd.
Cary, IL 60013
Myrtle Beach, SC 29577
Melville, NY 11747
Santa Clara, CA 96056
tel: (708) 639-2361
tel: (803) 448-9411
tel: (516) 847-3222
tel: (800) 554-5565
fax: (708) 639-1469
fax: (803) 448-1943
fax: (516) 847-3150
Coiltronics
Sanyo Video Components Corp.
International Rectifier Corp.
Zetex
6000 Park of Commerce Blvd.
2001 Sanyo Ave.
233 Kansas St.
87 Modular Ave.
Boca Raton, FL 33487
San Diego, CA 92173
El Segundo, CA 90245
Commack, NY 11725
tel: (407) 241-7876
tel: (619) 661-6835
tel: (310) 322-3331
tel: (516) 543-7100
fax: (407) 241-9339
fax: (619) 661-1055
fax: (310) 322-3332
Sumida
Sprague Electric
Motorola Inc.
Suite 209
Lower Main St.
MS 56-126
637 E. Golf Road
60005 Sanford, ME 04073
3102 North 56th St.
Arlington Heights, IL
tel: (207) 324-4140
Phoenix, AZ 85018
tel: (708) 956-0666
tel: (602) 244-3576
fax: (708) 956-0702
fax: (602) 244-4015
MIC2570
Micrel
MIC2570
14
1997
Component Side and Silk Screen (Not Actual Size)
Solder Side and Silk Screen (Not Actual Size)
Evaluation Board Layout
1997
15
MIC2570
MIC2570
Micrel
Package Information
45
0
8
0.244 (6.20)
0.228 (5.79)
0.197 (5.0)
0.189 (4.8)
SEATING
PLANE
0.026 (0.65)
MAX
)
0.010 (0.25)
0.007 (0.18)
0.064 (1.63)
0.045 (1.14)
0.0098 (0.249)
0.0040 (0.102)
0.020 (0.51)
0.013 (0.33)
0.157 (3.99)
0.150 (3.81)
0.050 (1.27)
TYP
PIN 1
DIMENSIONS:
INCHES (MM)
0.050 (1.27)
0.016 (0.40)
8-Pin SOP (M)
MIC2570
Micrel
MIC2570
16
1997
MICREL INC.
1849 FORTUNE DRIVE
SAN JOSE, CA 95131
USA
TEL
+ 1 (408) 944-0800
FAX
+ 1 (408) 944-0970
WEB
http://www.micrel.com
This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or
other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.
1997 Micrel Incorporated
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