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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 130A. The MIC2570 is available in selectable fixed output or adjustable 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 configured 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 in2 area. All versions are available in an 8-lead SOIC with an operating range from -40C to +85.
Features
* Operates from a two-cell supply 1.3V to 15V operation * 130A typical quiescent current * Complete regulator fits 0.6 in2 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 47H
8
D1 MBRA140 5V/100mA
1
L1 50H
C2 100F 10V MBRA140
2 3
2.0V-3.1V 2 AA Cells
C1 100F 10V
IN MIC2570-1
SW 2.85V 3.3V 5V
1 6 5 4
U1 2.5V to 4.2V 1 Li Cell C2 220F 10V C1 100F 10V IN
8
D1 L1 SW
1 4
VOUT 3.3V/80mA
MIC2570 3.3V SYNC GND
7 2
5
SYNC
7
GND
2
C3 330F 6.3V
Two-Cell to 5V DC-to-DC Converter
Single-Cell Lithium to 3.3V/80mARegulator
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MIC2570
Micrel
Ordering Information
Part Number MIC2570-1BM MIC2570-2BM Temperature Range -40C to +85C -40C to +85C Voltage Selectable* Adjustable Frequency 20kHz 20kHz Package 8-lead SOIC 8-lead SOIC
* Externally selectable for 2.85V, 3.3V, or 5V
Pin Configuration
MIC2570-1
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
MIC2570-2
8 7 6 5 IN SYNC FB NC
Selectable Voltage 20kHz Frequency
Adjustable Voltage 20kHz Frequency
8-Lead SOIC (M)
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.
4
Example: (-1) indicates the pin description is applicable to the MIC2570-1 only.
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Micrel
Absolute Maximum Ratings
Supply Voltage (VIN) ..................................................... 18V Switch Voltage (VSW) .................................................... 36V Switch Current (ISW) ....................................................... 1A Sync Voltage (VSYNC) .................................... -0.3V to 15V Storage Temperature (TA) ....................... -65C to +150C SOIC Power Dissipation (PD) .................................. 400mW
Operating Ratings
Supply Voltage (VIN) .................................... +1.3V to +15V Ambient Operating Temperature (TA) ........ -40C to +85C Junction Temperature (TJ) ....................... -40C to +125C SOIC Thermal Resistance (JA) ............................ 140C/W
Electrical Characteristics
VIN = 2.5V; TA = 25C, bold indicates -40C TA 85C; unless noted Parameter Input Voltage Quiescent Current Fixed Feedback Voltage Condition Startup guaranteed, ISW = 100mA Output switch off MIC2570-1; V2.85V pin = VOUT, ISW = 100mA MIC2570-1; V3.3V pin = VOUT, ISW = 100mA MIC2570-1; V5V pin = VOUT, ISW = 100mA MIC2570-2, [adj. voltage versions], ISW = 100mA, Note 1 MIC2570-2, [adj. voltage versions] MIC2570-1; V2.85V pin = VOUT, ISW = 100mA MIC2570-1; V3.3V pin = VOUT, ISW = 100mA MIC2570-1; V5V pin = VOUT, ISW = 100mA MIC2570-1; V2.85V pin = VOUT MIC2570-1; V3.3V pin = VOUT MIC2570-1; V5V pin = VOUT MIC2570-2 [adj. voltage versions]; VFB = 0V 1.5V VIN 15V VIN = 1.3V, ISW = 300mA VIN = 1.5V, ISW = 800mA VIN = 3.0V, ISW = 800mA Output switch off, VSW = 36V MIC2570-1, -2; ISW = 100mA Min 1.3 130 2.85 3.30 5.00 220 220 6 65 75 120 6 6 6 25 0.35 250 450 450 1 20 36 0.7 35 1.1 VFB < VREF, ISW = 100mA 67 Typ Max 15 Units V A V V V mV mV mV mV mV mV A A A nA %/V mV mV mV A kHz V V s 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
General Note: Devices are ESD protected; however, handling precautions are recommended. Note 1: Measured using comparator trip point.
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Micrel
Typical Characteristics
Switch Saturation Voltage
2.0 SWITCH CURRENT (A) SWITCH CURRENT (A) TA = -40C 1.5 2.0
Switch Saturation Voltage
2.0 2.5V VIN = 3.0V 2.0V 1.5V SWITCH CURRENT (A) TA = 25C 1.5
Switch Saturation Voltage
TA = 85C
1.5
VIN = 3.0V 1.5V
1.0
VIN= 3.0V
2.5V
1.0
1.0
0.5 1.5V 0
2.0V
0.5
0.5
0
0.2 0.4 0.6 0.8 SWITCH VOLTAGE (V)
1.0
0
0
0.2 0.4 0.6 0.8 SWITCH VOLTAGE (V)
1.0
0
0
0.2 0.4 0.6 0.8 SWITCH VOLTAGE (V)
1.0
Oscillator Frequency vs. Temperature
30 OSC. FREQUENCY (kHz) VIN = 2.5V ISW = 100mA 25 75 70 65 60 55
Oscillator Duty Cycle vs. Temperature
200 VIN = 2.5V ISW = 100mA QUIESCENT CURRENT (A) 175 150 125 100 75
Quiescent Current vs. Temperature
VIN = 2.5V
DUTY CYCLE (%)
20
4
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 (A) FEEDBACK CURRENT (nA) 8 6 4 2 0 -60 -30 0 30 60 90 120 150 TEMPERATURE (C) VIN = 2.5V MIC2570-1 50 40 30 20 10
Feedback Current vs. Temperature
200 VIN = 2.5V MIC2570-2 QUIESCENT CURRENT (A) 175 150 125 100 75 50 25 0 0
Quiescent Current vs. Supply Voltage
-40C +25C +85C
0 -60 -30 0 30 60 90 120 150 TEMPERATURE (C)
2 4 6 8 SUPPLY VOLTAGE (V)
10
SWITCH LEAKAGE CURRENT (nA)
Output Current Limit vs. Temperature
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 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) 2.85V
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MIC2570
Micrel
Block Diagrams
VBATT IN SYNC MIC2570-1 Oscillator 0.22V Reference VOUT
Driver
SW
5V
3.3V
2.85V
GND
Selectable Voltage Version with External Components
VBATT IN SYNC MIC2570-2 Oscillator 0.22V Reference
VOUT
Driver
SW
FB
GND
Adjustable Voltage Version with External Components
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Micrel
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 comparator 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 VOUT experiences about 120mV of hysteresis for a 5V output.
Supply Voltage
5V
VIN
0V IPEAK 0mA
Output Voltage
Inductor Current
5V 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 frequency. 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 combinations 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 VOUT + VDIODE - VIN VOUT + VDIODE - VSAT
4
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 approximately 3x 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 VIN or a switching waveform running at a frequency and duty cycle set by the oscillator. The continuous voltage equal to VIN happens when the voltage at the output (VOUT) 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 VOUT 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.
Current "ratchet" without current limit
Inductor Current
Current Limit Threshold
Continuous Current
Discontinuous Current Time
Figure 2. Current Limit Behavior 1997 4-67
MIC2570
Figure 2 shows an example of inductor current in the continuous 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 ~3x the input voltage. Selection of an inductor with a saturation threshold above 1.2A will insure that the system can withstand these conditions. Inductors, Capacitors and Diodes The importance of choosing correct inductors, capacitors and diodes can not be ignored. Poor choices for these components can cause problems as severe as circuit failure or as subtle as poorer than expected efficiency.
Micrel
capacitors are typically better. Figure 4 demonstrates the effect of capacitor ESR on output ripple voltage.
5.25 OUTPUT VOLTAGE (V)
5.00
a. Inductor Current
4.75
0
500 1000 TIME (s)
1500
Figure 4. Output Ripple
b.
c.
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 saturates, 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 significantly 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 electrolytic capacitors usually are the worst choice while tantalum
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 rectification 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 xt L
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:
V1 = VIN - VSAT
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 VOUT. Therefore, when the output switch is off, the voltage across the inductor is:
V2 = VOUT + VDIODE - VIN
For normal operation the inductor current is a triangular waveform which returns to zero current (discontinuous mode)
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MIC2570
at each cycle. At the threshold between continuous and discontinuous operation we can use the fact that I1 = I2 to get: L= V x t1 I
Micrel
V1 x t1 = V2 x t 2 t V1 =2 t1 V2
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 t1 is when VIN is at its minimum value and the worst case for t2 is when VIN is at its maximum value (assuming that VOUT, VDIODE and VSAT 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 IIN(max) = VOUT x IOUT(max) VIN(min) x Efficiency
L=
VIN(min) 2 x Average IIN(max)
x t1
where t1 =
duty cycle fOSC
To illustrate the use of these equations a design example will be given: Assume: MIC2570-1 (fixed oscillator) VOUT = 5V IOUT(max) =50mA VIN(min) = 1.8V efficiency = 75%. Average IIN(max) = L= 5V x 50mA = 185.2mA 1.8V x 0.75
1.8V x 0.7 2 x 185.2mA x 20kHz L = 170H Use the next lowest standard value of inductor and verify that it does not saturate at a current below about 400mA (< 2 x 185.2mA).
4
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:
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Application Examples
L1 47H 2.0V to 3.1V 2 Cells C1 100F 10V U1
8
MBRA140 D1
1
VOUT 5V/100mA 2.0V to 3.1V 2 Cells C1 100F 10V U1
8
L1 47H
MBRA140 D1 VOUT 3.3V/150mA
IN SW MIC2570 5V SYNC
7
IN SW MIC2570 3.3V GND
2
1
4
5
GND
2
C2 220F 10V U1 C1 C2 D1 L1 Micrel AVX AVX Motorola Coilcraft
SYNC
7
C2 330F 6.3V
U1 C1 C2 D1 L1
Micrel AVX AVX Motorola Coilcraft
MIC2570-1BM TPSD107M010R0100 Tantalum, ESR = 0.1 TPSE227M010R0100 Tantalum, ESR = 0.1 MBRA140T3 DO3316P-473, DCR = 0.12
MIC2570-1BM TPSD107M010R0100 Tantalum, ESR = 0.1 TPSE337M006R0100 Tantalum, ESR = 0.1 MBRA140T3 DO3316P-473, DCR = 0.12
Example 1. 5V/100mA Regulator
Example 2. 3.3V/150mA Regulator
C2 100F 10V MBRA140
2 3
L1 47H U1 2.0V to 3.1V 2 Cells C1 100F 10V
8
MBRA140 D1
1
VOUT 12V/40mA R2 1M 1% U1 C2 33F 25V 2.5V to 4.2V 1 Li Cell C1 100F 10V IN
1
L1 50H
8
D1 L1 SW
1 4
VOUT 3.3V/80mA
IN SW MIC2570 FB SYNC
7
6
MIC2570 3.3V SYNC GND
7 2
5
GND
2
R1 18.7k 1% U1 C1 C2 C3 D1 L1 Micrel AVX AVX AVX Motorola Coiltronics
C3 330F 6.3V
U1 C1 C2 D1 L1
Micrel AVX AVX Motorola Coilcraft
VOUT = 0.22V (1+R2/R1) MIC2570-2BM TPSD107M010R0100 Tantalum, ESR = 0.11 TPSE336M025R0300 Tantalum, ESR = 0.3 MBRA140T3 DO3316P-473, DCR = 0.12
MIC2570-1BM TPSD107M010R0100 Tantalum, ESR = 0.1 TPSD107M010R0100 Tantalum, ESR = 0.1 TPSE337M006R0100 Tantalum, ESR = 0.1 MBRA140T3 CTX50-4P DCR = 0.097
Example 3. 12V/40mA Regulator
Example 4. Single Cell Lithium to 3.3V/80mA Regulator
U2 L1 47H U1 2.0V to 3.1V 2 Cells C1 100F 10V
8
MBRA140 D1
6V
3 2
IN EN
OUT MIC5203 GND
4
VOUT 5V/80mA C3 1F 16V
IN SW MIC2570 FB SYNC GND
7 2
1
R2 523k 1%
6
C2 220F 10V
1
R1 20k 1%
VOUT = 0.22V
(1+R2/R1)
U1 U2 C1 C2 C3 D1 L1
Micrel Micrel AVX AVX Sprague Motorola Coilcraft
MIC2570-2BM MIC5203-5.0BM4 TPSD107M010R0100 Tantalum ESR = 0.1 TPSE227M010R0300 Tantalum ESR = 0.1 293D105X0016A2W Tantalum MBRA140T3 DO3316P-473 DCR = 0.12
Example 5. Low-Noise 5V/80mA Regulator
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MIC2570
U2 L1 47H U1 2.0V to 3.1V 2 Cells C1 100F 10V
8
Micrel
D1 MBRA140
1
4.3V
3 2
IN EN
OUT MIC5203 GND
4
VOUT 3.3V/80mA C3 1F 16V
IN SW MIC2570 FB SYNC GND
7 2
R2 374k 1%
6
C2 220F 10V VOUT = 0.22V
1
R1 20k 1%
(1+R2/R1)
U1 U2 C1 C2 C3 D1 L1
Micrel Micrel AVX AVX Sprague Motorola Coilcraft
MIC2570-2BM MIC5203-3.3BM4 TPSD107M010R0100 Tantalum ESR = 0.1 TPSE227M010R0100 Tantalum ESR = 0.1 293D105X0016A2W Tantalum MBRA140T3 DO3316P-473 DCR = 0.12
Example 6. Low-Noise 3.3V/80mA Regulator
L1 47H U1 2.0V to 3.1V 2 Cells C1 100F 16V
8
MBRA140 D1
1
+VOUT 5V/50mA
IN SW MIC2570 5V SYNC GND
7 2
C3 220F 10V
-IOUT +IOUT
4
D2 MBRA140
C2 220F 10V C4 220F 10V D3 MBRA140
U1 C1 C2 C3 C4 D1 D2 D3 L1
Micrel AVX AVX AVX AVX Motorola Motorola Motorola Coilcraft
MIC2570-1BM TPSD107M010R0100 Tantalum, ESR = 0.1 TPSE227M010R0100 Tantalum, ESR = 0.1 TPSE227M010R0100 Tantalum, ESR = 0.1 TPSE227M010R0100 Tantalum, ESR = 0.1 MBRA140T3 MBRA140T3 MBRA140T3 DO3316P-473, DCR = 1.2
4
-VOUT -4.5V to -5V/50mA
Example 7. 5V/50mA Regulator
2.0V to 3.1V 2 Cells U1 C1 100F 10V
8
L1 47H IN SW MIC2570 FB SYNC
7
D3 1N4148
1
C1 22F 35V
R2 549k 1%
6
C3 0.1F
GND
2
D1 MBRA140 D2 MBRA140
R1 4.99k 1% R3 220k C2 22F 35V
-VOUT = -0.22V U1 C1 C2 C3 D1 D2 L1
(1+R2/R1) + 0.6V
Micrel AVX AVX AVX Motorola Motorola Coilcraft
MIC2570-2BM TPSD107M010R0100, Tantalum ESR = 0.1 TPSE226M035R0300, Tantalum ESR = 0.3 TPSE226M035R0300, Tantalum ESR = 0.3 MBRA140T3 MBRA140T3 DO3316P-473, DCR = 0.12
-VOUT -24V/20mA
Example 8. -24V/20mA Regulator
1997
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MIC2570
C2 68F, 35V
Micrel
L1 47H U1 2.0V to 3.1V 2 Cell C1 330F 16V
8
D1 1N5819
1
D2 1N5819 C3 68F 35V
D3 1N5819 R2 2.2M 1% VOUT 50V/10mA
IN SW MIC2570 FB SYNC GND
7 2 6
C4 82F 63V
R1 10k 1% 1+R2/R1)
U1 C1 C2 C3 C4 D1 D2 D3 L1
Micrel Sanyo Sanyo Sanyo Sanyo Motorola Motorola Motorola Sumida
VOUT = 0.22 MIC2570-2BM 16MV330GX Electrolytic ESR = 0.1 35MV68GX Electrolytic ESR = 0.22 35MV68GX Electrolytic ESR = 0.22 63MV826X Electrolytic ESR = 0.34 1N5819 1N5819 1N5819 RCH106-470k DCR = 0.16
Example 9. Voltage Doubler
L1 U1 2.0V to 3.1V 2 Cell C1 100F 10V 47H
8
D1 MBRA140
IN SW MIC2570 FB SYNC GND
7 2
1
D2 LED X5 I LED R1 11k 1%
6
C2 220F 10V
U1 C1 C2 D1 L1
Micrel AVX AVX Motorola Coilcraft
I = 0.22V/R1 MIC2570-2BM TPSD107M010R0100 Tantalum ESR = 0.1 TPSE227M010R0100 Tantalum ESR = 0.1 MBRA140T3 DO3316P-473 DCR = 0.12
Example 10. Constant-Current LED Supply
L1 47H U1 2.0V to 3.1V 2 Cell C1 100F 10V
8
D1 VOUT 5V/100mA MBRA140
1
IN SW MIC2570 FB SYNC GND
7 2
R2 434k 1%
6
C2 220F 10V
D2 1N4148 R3 100k 74C04
R1 20k 1%
VOUT = 0.22V
(1+R2/R1)
Enable Shutdown
U1 C1 C2 D1 L1
Micrel AVX AVX Motorola Coilcraft
MIC2570-2BM TPSD107M010R0100 Tantalum ESR = 0.1 TPSE227M010R0100 Tantalum ESR = 0.1 MBRA140T3 DO3316P-473 DCR = 0.12
Example 11. 5V/100mA Regulator with Shutdown
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MIC2570
R1 510 L1 47H U1 2.0V to 3.1V 2 Cell C1 100F 10V
8
Micrel
D1 MBRA140
1
Q1 ZTX7888 R2 434k 1% R1 20k 1%
VOUT 5V/100mA
IN SW MIC2570 FB SYNC GND
7 2
6
D2 1N4148
C2 220F 10V
C3 220F 10V
VOUT = 0.22V
(1+R2/R1)
Enable Shutdown
74C04
R3 100k
U1 C1 C2 C3 D1 L1 Q1
Micrel AVX AVX AVX Motorola Coilcraft Zetex
MIC2570-2BM TPSD107M010R0100 Tantalum ESR = 0.1 TPSE227M010R0100 Tantalum ESR = 0.1 TPSE227M010R0100 Tantalum ESR = 0.1 MBRA140T3 DO3316P-473 DCR = 0.12 ZTX7888
Example 12. 5V/100mA Regulator with Shutdown and Output Disconnect
D2 MBRS130L 2.0V to 3.1V 2 Cell C1 100F 10V L1 47H U1
8
D1 MBRA140
1
VOUT 5V/70mA
IN SW MIC2570 5V SYNC
7
4
4
C2 220F 10V
GND
2
U1 C1 C2 D1 D2 L1
Micrel AVX AVX Motorola Motorola Coilcraft
MIC2570-1BM TPSD107M010R0100 Tantalum ESR = 0.1 TPSE227M010R0100 Tantalum ESR = 0.1 MBRA140T3 MBRS130L DO3316P-473 DCR = 0.12
Example 13. Reversed-Battery Protected Regulator
body diode
L1 Q1 Si9434 2.0V to 3.1V 2 Cell C3 0.1F C1 100F 10V
7
D1 MBRA140
1
D3 1N4148
U1
47H
8
VOUT 5V/100mA
IN SW MIC2570 5V SYNC GND
2 4
C4 0.1F
R1 100k
D2 1N4148
C2 220F 10V
U1 C1 C2 D1 D2 D3 L1 Q1
Micrel AVX AVX Motorola Motorola Motorola Coilcraft Siliconix
MIC2570-1BM TPSD107M010R0100 Tantalum ESR = 0.1 TPSE227M010R0100 Tantalum ESR = 0.1 MBRA140T3 MBRS130LT3 MBRS130LT3 DO3316P-473 DCR = 0.12 Si9434 PMOS
Example 14. Improved Reversed-Battery Protected Regulator
1997
4-73
MIC2570
Micrel
Component Cross Reference
Capacitors
AVX Surface Mount (Tantalum)
330F/6.3V 220F/10V 100F/10V 33F/25V 22F/35V Diodes TPSE337M006R0100 TPSE227M010R0100 TPSD107M010R0100 TPSE336M025R0300 TPSE226M035R0300
Sprague Surface Mount (Tantalum)
593D337X06R3E2W 593D227X0010E2W 593D107X0010D2W 593D336X0025E2W 593D226X0035E2W
Sanyo Through Hole (OS-CON)
10SA220M 10SA220M 10SA100M
Sanyo Through Hole (AL Electrolytic)
16MV330GX (330F/16V) 16MV330GX (330F/16V) 16MV330GX (330F/16V) 35MV68GX (68F/35V) 35MV68GX (68F/35V)
Motorola Surface Mount (Schottky)
1A/40V 1A/20V Inductors MBRA140T3
GI Surface Mount (Schottky)
SS14
IR Surface Mount (Schottky)
10MQ40
Motorola Through Hole (Schottky)
1N5819 1N5817
Coilcraft Surface Mount (Button Cores)
22H 47H 50H DO3308P-223 DO3316P-473
Coiltronics Surface Mount (Torriod)
Sumida Surface Mount (Button Cores)
CD75-470LC
Sumida Through Hole (Button Cores)
RCH-106-470k
CTX50-4P
Suggested Manufacturers List
Inductors Capacitors Diodes Transistors
Coilcraft 1102 Silver Lake Rd. Cary, IL 60013 tel: (708) 639-2361 fax: (708) 639-1469 Coiltronics 6000 Park of Commerce Blvd. Boca Raton, FL 33487 tel: (407) 241-7876 fax: (407) 241-9339 Sumida Suite 209 637 E. Golf Road Arlington Heights, IL tel: (708) 956-0666 fax: (708) 956-0702
AVX Corp. 801 17th Ave. South Myrtle Beach, SC 29577 tel: (803) 448-9411 fax: (803) 448-1943 Sanyo Video Components Corp. 2001 Sanyo Ave. San Diego, CA 92173 tel: (619) 661-6835 fax: (619) 661-1055 Sprague Electric Lower Main St. 60005 Sanford, ME 04073 tel: (207) 324-4140
General Instruments (GI) 10 Melville Park Rd. Melville, NY 11747 tel: (516) 847-3222 fax: (516) 847-3150 International Rectifier Corp. 233 Kansas St. El Segundo, CA 90245 tel: (310) 322-3331 fax: (310) 322-3332 Motorola Inc. MS 56-126 3102 North 56th St. Phoenix, AZ 85018 tel: (602) 244-3576 fax: (602) 244-4015
Siliconix 2201 Laurelwood Rd. Santa Clara, CA 96056 tel: (800) 554-5565 Zetex 87 Modular Ave. Commack, NY 11725 tel: (516) 543-7100
4-74
1997
MIC2570
Micrel
Evaluation Board Layout
Component Side and Silk Screen (Not Actual Size)
4
Solder Side and Silk Screen (Not Actual Size)
1997
4-75

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