MIC2570 Micrel MIC2570 Two-Cell Switching Regulator Preliminary Information General Description Features 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. • Operates from a two-cell supply 1.3V to 15V operation • 130µA 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 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 –40°C to +85°. 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 D1 MBRA140 5V/100mA 1 L1 50µH C2 100µF 10V MBRA140 2 3 8 2.0V–3.1V 2 AA Cells C1 100µF 10V IN MIC2570-1 SW 1 2.85V 6 3.3V 5 5V SYNC 7 4 GND 2 U1 2.5V to 4.2V 1 Li Cell C1 100µF 10V D1 8 L1 IN SW MIC2570 3.3V SYNC GND C2 220µF 10V 7 Two-Cell to 5V DC-to-DC Converter VOUT 3.3V/80mA 2 1 4 5 C3 330µF 6.3V Single-Cell Lithium to 3.3V/80mARegulator 4-62 1997 MIC2570 Micrel 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 MIC2570-1 MIC2570-2 SW 1 8 IN SYNC GND 2 7 SYNC 6 2.85V NC 3 6 FB 5 3.3V NC 4 5 NC SW 1 8 IN GND 2 7 NC 3 5V 4 Adjustable Voltage 20kHz Frequency Selectable Voltage 20kHz Frequency 8-Lead SOIC (M) Pin Description † Pin No. (Version†) Pin Name 1 SW 2 GND 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 5 (-2) NC 6 (-1) 2.85V 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 Pin Function Switch: NPN output switch transistor collector. Power Ground: NPN output switch transistor emitter. 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. Supply (Input): Positive supply voltage input. Example: (-1) indicates the pin description is applicable to the MIC2570-1 only. 1997 4-63 4 MIC2570 Micrel Absolute Maximum Ratings Operating Ratings Supply Voltage (VIN) ..................................................... 18V Switch Voltage (VSW) .................................................... 36V Switch Current (ISW) ....................................................... 1A Sync Voltage (VSYNC) .................................... –0.3V to 15V Storage Temperature (TA) ....................... –65°C to +150°C SOIC Power Dissipation (PD) .................................. 400mW Supply Voltage (VIN) .................................... +1.3V to +15V Ambient Operating Temperature (TA) ........ –40°C to +85°C Junction Temperature (TJ) ....................... –40°C to +125°C SOIC Thermal Resistance (θJA) ............................ 140°C/W Electrical Characteristics VIN = 2.5V; TA = 25°C, bold indicates –40°C ≤ TA ≤ 85°C; unless noted Parameter Condition Min Typ Input Voltage Startup guaranteed, ISW = 100mA 1.3 Quiescent Current Output switch off 130 µA Fixed Feedback Voltage MIC2570-1; V2.85V pin = VOUT, ISW = 100mA MIC2570-1; V3.3V pin = VOUT, ISW = 100mA MIC2570-1; V5V pin = VOUT, ISW = 100mA 2.85 3.30 5.00 V V V Reference Voltage MIC2570-2, [adj. voltage versions], ISW = 100mA, Note 1 220 220 mV mV Comparator Hysteresis MIC2570-2, [adj. voltage versions] 6 mV Output Hysteresis MIC2570-1; V2.85V pin = VOUT, ISW = 100mA MIC2570-1; V3.3V pin = VOUT, ISW = 100mA MIC2570-1; V5V pin = VOUT, ISW = 100mA 65 75 120 mV mV mV Feedback Current MIC2570-1; V2.85V pin = VOUT MIC2570-1; V3.3V pin = VOUT MIC2570-1; V5V pin = VOUT MIC2570-2 [adj. voltage versions]; VFB = 0V 6 6 6 25 µA µA µA nA Reference Line Regulation 1.5V ≤ VIN ≤ 15V 0.35 %/V Switch Saturation Voltage VIN = 1.3V, ISW = 300mA VIN = 1.5V, ISW = 800mA VIN = 3.0V, ISW = 800mA 250 450 450 mV mV mV Switch Leakage Current Output switch off, VSW = 36V 1 µA Oscillator Frequency MIC2570-1, -2; ISW = 100mA 20 kHz Maximum Output Voltage Max Units 15 V 36 V Sync Threshold Voltage 0.7 V Switch On-Time 35 µs Currrent Limit 1.1 A 67 % Duty Cycle VFB < VREF, ISW = 100mA General Note: Devices are ESD protected; however, handling precautions are recommended. Note 1: Measured using comparator trip point. 4-64 1997 MIC2570 Micrel Typical Characteristics Switch Saturation Voltage Switch Saturation Voltage TA = –40°C 1.5 VIN= 3.0V 0.5 1.5V 0 0 2.5V 2.0V 0.2 0.4 0.6 0.8 SWITCH VOLTAGE (V) TA = 25°C 1.5 0 1.0 0 0.2 0.4 0.6 0.8 SWITCH VOLTAGE (V) VIN = 3.0V 1.5 1.5V 1.0 0.5 0 1.0 0 25 20 70 0.2 0.4 0.6 0.8 SWITCH VOLTAGE (V) 1.0 Quiescent Current vs. Temperature 75 VIN = 2.5V ISW = 100mA DUTY CYCLE (%) 200 VIN = 2.5V ISW = 100mA 65 60 55 VIN = 2.5V 175 150 125 4 100 75 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 Feedback Current vs. Temperature Quiescent Current vs. Supply Voltage 6 4 2 Output Current Limit vs. Temperature 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 -60 -30 0 30 60 90 120 150 TEMPERATURE (°C) 30 20 10 0 -60 -30 0 30 60 90 120 150 TEMPERATURE (°C) SWITCH LEAKAGE CURRENT (nA) 0 -60 -30 0 30 60 90 120 150 TEMPERATURE (°C) 40 200 VIN = 2.5V MIC2570-2 QUIESCENT CURRENT (µA) FEEDBACK CURRENT (nA) 8 50 VIN = 2.5V MIC2570-1 –40°C 175 +25°C 150 125 +85°C 100 75 50 25 0 Switch Leakage Current vs. Temperature 0 2 4 6 8 SUPPLY VOLTAGE (V) 10 Output Hysteresis vs. Temperature 1000 150 OUTPUT HYSTERESIS (mV) OSC. FREQUENCY (kHz) 1.5V TA = 85°C Oscillator Duty Cycle vs. Temperature 10 FEEDBACK CURRENT (µA) 2.0V 0.5 30 CURRENT LIMIT (A) VIN = 3.0V 1.0 Oscillator Frequency vs. Temperature 1997 2.5V QUIESCENT CURRENT (µA) 1.0 Switch Saturation Voltage 2.0 SWITCH CURRENT (A) 2.0 SWITCH CURRENT (A) SWITCH CURRENT (A) 2.0 100 10 1 0.1 0.01 -60 -30 0 30 60 90 120 150 TEMPERATURE (°C) 4-65 125 5V 100 3.3V 75 50 2.85V 25 0 -60 -30 0 30 60 90 120 150 TEMPERATURE (°C) MIC2570 Micrel Block Diagrams VBATT VOUT IN SYNC MIC2570-1 Oscillator 0.22V Reference 5V 3.3V Driver SW 2.85V GND Selectable Voltage Version with External Components VBATT VOUT IN SYNC MIC2570-2 Oscillator 0.22V Reference Driver FB SW GND Adjustable Voltage Version with External Components 4-66 1997 MIC2570 Micrel 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. 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 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 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. Supply Voltage IPEAK VIN 0V 0mA 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 Current “ratchet” without current limit Current Limit Threshold Inductor Current 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. 5V Output Voltage 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. Inductor Current Functional Description Continuous Current Discontinuous Current Time Figure 2. Current Limit Behavior 1997 4-67 4 MIC2570 Micrel capacitors are typically better. Figure 4 demonstrates the effect of capacitor ESR on output ripple voltage. 5.25 OUTPUT VOLTAGE (V) 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 ~3× 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. 4.75 a. Inductor Current 5.00 0 500 1000 TIME (µs) 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 200mΩ ESR can cause 100mV of ripple at the output due the capacitor only. Acceptable values of ESR are typically in the 50mΩ 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 × t 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) 4-68 1997 MIC2570 Micrel at each cycle. At the threshold between continuous and discontinuous operation we can use the fact that I1 = I2 to get: L = V × t1 I V1 × t1 = V2 × t 2 L = 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) = 2 × Average IIN(max) where t1 = × 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) = 5V × 50mA = 185.2mA 1.8V × 0.75 1.8V × 0.7 2 × 185.2mA × 20kHz L = 170µH L = VOUT × IOUT(max) VIN(min) × Efficiency 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: 1997 VIN(min) Use the next lowest standard value of inductor and verify that it does not saturate at a current below about 400mA (< 2 × 185.2mA). 4-69 4 MIC2570 Micrel Application Examples MBRA140 L1 47µH U1 C1 100µF 10V 2.0V to 3.1V 2 Cells D1 8 IN SW 2.0V to 3.1V 2 Cells 1 U1 C1 100µF 10V IN SW U1 C1 C2 D1 L1 Micrel AVX AVX Motorola Coilcraft 4 GND 7 C2 220µF 10V 2 7 MIC2570-1BM TPSD107M010R0100 Tantalum, ESR = 0.1Ω TPSE227M010R0100 Tantalum, ESR = 0.1Ω MBRA140T3 DO3316P-473, DCR = 0.12Ω U1 C1 C2 D1 L1 47µH 2.0V to 3.1V 2 Cells SW MIC2570 FB SYNC 7 U1 C1 C2 D1 L1 Micrel AVX AVX Motorola Coilcraft 1 2.5V to 4.2V 1 Li Cell C2 33µF 25V C1 100µF 10V 2 VOUT 3.3V/80mA D1 8 L1 IN SW MIC2570 3.3V SYNC GND R1 18.7k 1% 2 C2 100µF 10V MBRA140 L1 50µH 3 U1 6 GND C2 330µF 6.3V MIC2570-1BM TPSD107M010R0100 Tantalum, ESR = 0.1Ω TPSE337M006R0100 Tantalum, ESR = 0.1Ω MBRA140T3 DO3316P-473, DCR = 0.12Ω VOUT 12V/40mA R2 1M 1% 1 5 Example 2. 3.3V/150mA Regulator D1 8 IN Micrel AVX AVX Motorola Coilcraft 1 2 MBRA140 L1 U1 3.3V GND SYNC Example 1. 5V/100mA Regulator C1 100µF 10V D1 8 MIC2570 5V VOUT 3.3V/150mA 47µH MIC2570 SYNC MBRA140 L1 VOUT 5V/100mA 7 VOUT = 0.22V (1+R2/R1) MIC2570-2BM TPSD107M010R0100 Tantalum, ESR = 0.11Ω TPSE336M025R0300 Tantalum, ESR = 0.3Ω MBRA140T3 DO3316P-473, DCR = 0.12Ω U1 C1 C2 C3 D1 L1 Micrel AVX AVX AVX Motorola Coiltronics 1 4 5 2 C3 330µF 6.3V MIC2570-1BM TPSD107M010R0100 Tantalum, ESR = 0.1Ω TPSD107M010R0100 Tantalum, ESR = 0.1Ω TPSE337M006R0100 Tantalum, ESR = 0.1Ω MBRA140T3 CTX50-4P DCR = 0.097Ω Example 4. Single Cell Lithium to 3.3V/80mA Regulator Example 3. 12V/40mA Regulator U2 MBRA140 L1 6V 3 47µH U1 2.0V to 3.1V 2 Cells C1 100µF 10V IN SW MIC2570 FB SYNC GND 7 U1 U2 C1 C2 C3 D1 L1 Micrel Micrel AVX AVX Sprague Motorola Coilcraft 2 D1 8 2 1 R2 523k 1% 6 IN OUT MIC5203 4 EN C3 1µF 16V GND C2 220µF 10V R1 20k 1% 1 VOUT = 0.22V VOUT 5V/80mA (1+R2/R1) MIC2570-2BM MIC5203-5.0BM4 TPSD107M010R0100 Tantalum ESR = 0.1Ω TPSE227M010R0300 Tantalum ESR = 0.1Ω 293D105X0016A2W Tantalum MBRA140T3 DO3316P-473 DCR = 0.12Ω Example 5. Low-Noise 5V/80mA Regulator 4-70 1997 MIC2570 Micrel U2 L1 D1 47µH U1 2.0V to 3.1V 2 Cells IN SW MIC2570 FB U1 U2 C1 C2 C3 D1 L1 Micrel Micrel AVX AVX Sprague Motorola Coilcraft 2 R2 374k 1% 1 EN OUT MIC5203 VOUT = 0.22V VOUT 3.3V/80mA 4 C3 1µF 16V 1 C2 220µF 10V R1 20k 1% 2 IN GND 6 SYNC GND 7 3 MBRA140 8 C1 100µF 10V 4.3V (1+R2/R1) MIC2570-2BM MIC5203-3.3BM4 TPSD107M010R0100 Tantalum ESR = 0.1Ω TPSE227M010R0100 Tantalum ESR = 0.1Ω 293D105X0016A2W Tantalum MBRA140T3 DO3316P-473 DCR = 0.12Ω Example 6. Low-Noise 3.3V/80mA Regulator MBRA140 L1 47µH U1 C1 100µF 16V 2.0V to 3.1V 2 Cells D1 8 IN SW MIC2570 5V +VOUT 5V/50mA C3 220µF 10V 1 –IOUT ≤ +IOUT 4 SYNC GND 7 U1 C1 C2 C3 C4 D1 D2 D3 L1 Micrel AVX AVX AVX AVX Motorola Motorola Motorola Coilcraft 2 C2 220µF 10V D2 MBRA140 4 C4 220µF 10V MIC2570-1BM TPSD107M010R0100 Tantalum, ESR = 0.1Ω TPSE227M010R0100 Tantalum, ESR = 0.1Ω TPSE227M010R0100 Tantalum, ESR = 0.1Ω TPSE227M010R0100 Tantalum, ESR = 0.1Ω MBRA140T3 MBRA140T3 MBRA140T3 DO3316P-473, DCR = 1.2Ω –VOUT –4.5V to –5V/50mA D3 MBRA140 Example 7. ±5V/50mA Regulator D3 L1 2.0V to 3.1V 2 Cells 47µH U1 IN SW C1 100µF 10V MIC2570 FB SYNC 7 –VOUT = –0.22V U1 C1 C2 C3 D1 D2 L1 1N4148 8 1 GND 2 R2 549k 1% 6 D1 MBRA140 (1+R2/R1) + 0.6V Micrel AVX AVX AVX Motorola Motorola Coilcraft C1 22µF 35V D2 MBRA140 R1 4.99k 1% R3 220k MIC2570-2BM TPSD107M010R0100, Tantalum ESR = 0.1Ω TPSE226M035R0300, Tantalum ESR = 0.3Ω TPSE226M035R0300, Tantalum ESR = 0.3Ω MBRA140T3 MBRA140T3 DO3316P-473, DCR = 0.12Ω Example 8. –24V/20mA Regulator 1997 4-71 C3 0.1µF C2 22µF 35V –VOUT –24V/20mA MIC2570 Micrel C2 68µF, 35V L1 D1 47µH U1 2.0V to 3.1V 2 Cell 1N5819 8 C1 330µF 16V D2 1N5819 1 R2 2.2M 1% C4 82µF 63V MIC2570 6 FB SYNC GND 7 U1 C1 C2 C3 C4 D1 D2 D3 L1 VOUT 50V/10mA 1N5819 C3 68µF 35V IN SW D3 R1 10k 1% 2 VOUT = 0.22 MIC2570-2BM 16MV330GX Electrolytic ESR = 0.1Ω 35MV68GX Electrolytic ESR = 0.22Ω 35MV68GX Electrolytic ESR = 0.22Ω 63MV826X Electrolytic ESR = 0.34Ω 1N5819 1N5819 1N5819 RCH106-470k DCR = 0.16Ω Micrel Sanyo Sanyo Sanyo Sanyo Motorola Motorola Motorola Sumida 1+R2/R1) Example 9. Voltage Doubler D1 MBRA140 L1 47µH U1 8 C1 100µF 10V 2.0V to 3.1V 2 Cell IN SW MIC2570 FB 1 D2 LED X5 I LED 6 R1 11k 1% SYNC GND 7 U1 C1 C2 D1 L1 C2 220µF 10V 2 I = 0.22V/R1 MIC2570-2BM TPSD107M010R0100 Tantalum ESR = 0.1Ω TPSE227M010R0100 Tantalum ESR = 0.1Ω MBRA140T3 DO3316P-473 DCR = 0.12Ω Micrel AVX AVX Motorola Coilcraft Example 10. Constant-Current LED Supply L1 D1 VOUT 5V/100mA 47µH U1 2.0V to 3.1V 2 Cell IN SW MIC2570 FB SYNC GND 7 VOUT = 0.22V MBRA140 8 C1 100µF 10V 2 6 Micrel AVX AVX Motorola Coilcraft C2 220µF 10V R1 20k 1% D2 1N4148 R3 100k (1+R2/R1) 74C04 Enable Shutdown U1 C1 C2 D1 L1 R2 434k 1% 1 MIC2570-2BM TPSD107M010R0100 Tantalum ESR = 0.1Ω TPSE227M010R0100 Tantalum ESR = 0.1Ω MBRA140T3 DO3316P-473 DCR = 0.12Ω Example 11. 5V/100mA Regulator with Shutdown 4-72 1997 MIC2570 Micrel R1 510Ω L1 D1 47µH U1 2.0V to 3.1V 2 Cell 8 IN C1 100µF 10V 6 FB 7 VOUT = 0.22V 2 C2 220µF 10V R1 20k 1% D2 1N4148 (1+R2/R1) C3 220µF 10V R3 100k 74C04 Enable Shutdown Micrel AVX AVX AVX Motorola Coilcraft Zetex R2 434k 1% 1 SW MIC2570 SYNC GND U1 C1 C2 C3 D1 L1 Q1 VOUT 5V/100mA Q1 ZTX7888 MBRA140 MIC2570-2BM TPSD107M010R0100 Tantalum ESR = 0.1Ω TPSE227M010R0100 Tantalum ESR = 0.1Ω TPSE227M010R0100 Tantalum ESR = 0.1Ω MBRA140T3 DO3316P-473 DCR = 0.12Ω ZTX7888 Example 12. 5V/100mA Regulator with Shutdown and Output Disconnect D2 MBRS130L L1 47µH U1 C1 100µF 10V 2.0V to 3.1V 2 Cell SW MIC2570 5V Micrel AVX AVX Motorola Motorola Coilcraft 1 4 4 C2 220µF 10V GND 7 VOUT 5V/70mA MBRA140 8 IN SYNC U1 C1 C2 D1 D2 L1 D1 2 MIC2570-1BM TPSD107M010R0100 Tantalum ESR = 0.1Ω TPSE227M010R0100 Tantalum ESR = 0.1Ω MBRA140T3 MBRS130L DO3316P-473 DCR = 0.12Ω Example 13. Reversed-Battery Protected Regulator body diode D1 L1 Q1 Si9434 2.0V to 3.1V 2 Cell D3 C3 0.1µF 1N4148 C4 0.1µF U1 C1 C2 D1 D2 D3 L1 Q1 Micrel AVX AVX Motorola Motorola Motorola Coilcraft Siliconix R1 100k D2 1N4148 47µH U1 MBRA140 8 VOUT 5V/100mA IN SW C1 100µF 10V 1 MIC2570 5V SYNC 7 GND 2 4 C2 220µF 10V MIC2570-1BM TPSD107M010R0100 Tantalum ESR = 0.1Ω TPSE227M010R0100 Tantalum ESR = 0.1Ω MBRA140T3 MBRS130LT3 MBRS130LT3 DO3316P-473 DCR = 0.12Ω Si9434 PMOS Example 14. Improved Reversed-Battery Protected Regulator 1997 4-73 MIC2570 Micrel Component Cross Reference Capacitors AVX Surface Mount (Tantalum) Sprague Surface Mount (Tantalum) Sanyo Through Hole (OS-CON) Sanyo Through Hole (AL Electrolytic) 330µF/6.3V TPSE337M006R0100 593D337X06R3E2W 10SA220M 16MV330GX (330µF/16V) 220µF/10V TPSE227M010R0100 593D227X0010E2W 10SA220M 16MV330GX (330µF/16V) 100µF/10V TPSD107M010R0100 593D107X0010D2W 10SA100M 16MV330GX (330µF/16V) 33µF/25V TPSE336M025R0300 593D336X0025E2W 35MV68GX (68µF/35V) 22µF/35V TPSE226M035R0300 593D226X0035E2W 35MV68GX (68µF/35V) Motorola Surface Mount (Schottky) GI Surface Mount (Schottky) IR Surface Mount (Schottky) MBRA140T3 SS14 10MQ40 Diodes 1A/40V 1A/20V Motorola Through Hole (Schottky) 1N5819 1N5817 Inductors Coilcraft Surface Mount (Button Cores) 22µH DO3308P-223 47µH DO3316P-473 50µH Coiltronics Surface Mount (Torriod) Sumida Surface Mount (Button Cores) Sumida Through Hole (Button Cores) CD75-470LC 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 AVX Corp. 801 17th Ave. South Myrtle Beach, SC 29577 tel: (803) 448-9411 fax: (803) 448-1943 General Instruments (GI) 10 Melville Park Rd. Melville, NY 11747 tel: (516) 847-3222 fax: (516) 847-3150 Siliconix 2201 Laurelwood Rd. Santa Clara, CA 96056 tel: (800) 554-5565 Coiltronics 6000 Park of Commerce Blvd. Boca Raton, FL 33487 tel: (407) 241-7876 fax: (407) 241-9339 Sanyo Video Components Corp. 2001 Sanyo Ave. San Diego, CA 92173 tel: (619) 661-6835 fax: (619) 661-1055 International Rectifier Corp. 233 Kansas St. El Segundo, CA 90245 tel: (310) 322-3331 fax: (310) 322-3332 Zetex 87 Modular Ave. Commack, NY 11725 tel: (516) 543-7100 Sumida Suite 209 637 E. Golf Road Arlington Heights, IL tel: (708) 956-0666 fax: (708) 956-0702 Sprague Electric Lower Main St. 60005 Sanford, ME 04073 tel: (207) 324-4140 Motorola Inc. MS 56-126 3102 North 56th St. Phoenix, AZ 85018 tel: (602) 244-3576 fax: (602) 244-4015 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