MIC2142 Micropower Boost Converter General Description Features The MIC2142 is a micropower boost switching regulator • 2.2V to 16V input voltage housed in a SOT23-5 package. The input voltage range is • Up to 22V output voltage between 2.2V to 16V, making the device suitable for one• 330kHz switching frequency cell Li Ion and 3 to 4-cell alkaline/NiCad/NiMH applica• 0.1µA shutdown current tions. The output voltage of the MIC2142 can be adjusted • 85µA quiescent current up to 22V. • Implements low-power boost, SEPIC, or flyback The MIC2142 is well suited for portable, space-sensitive applications. It features a low quiescent current of 85µA, • SOT23-5 package and a typical shutdown current of 0.1µA. It’s 330kHz operation allows small surface mount external components Applications to be used. The MIC2142 is capable of efficiencies over 85% in a small board area. • LCD bias supply The MIC2142 can be configured to efficiently power a • White LED driver variety of loads. It is capable of providing a few mA output • 12V Flash memory supply for supplying low power bias voltages; it is also capable of • Local 3V to 5V conversion providing the 80mA needed to drive 4 white LEDs. The MIC2142 is available in a SOT23-5 package with an ambient operating temperature range from –40°C to +85°C. Data sheets and support documentation can be found on Micrel’s web site at www.micrel.com. ___________________________________________________________________________________________________________ Typical Application 1 CIN 10µF 5 D1 MIC2142 VCC SW 3 FB 4 EN GND 2 Typical Configuration +5V @60mA R2 365k R1 124k COUT 22µF EFFICIENCY (%) L1 33µH 2.8V to 4.7V VIN 0.90 0.85 0.80 0.75 0.70 0.65 0.60 0.55 0.50 0.45 0.40 0 Efficiency vs. Output Current VIN = 4.2V VIN = 3.0V 10 20 30 40 50 60 70 OUTPUT CURRENT (mA) Efficiency vs. Output Current Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com October 2007 M9999-102507 Micrel, Inc. MIC2142 Ordering Information Part Number Marking* Standard Pb-Free Standard Pb-Free MIC2142BM5 MIC2142YM5 SBAA SBAA Voltage Ambient Temperature Range Package Adj. –40° to +85°C 5-Pin SOT23 * Under bar symbol (_) may not be to scale. Pin Configuration 5-Pin SOT23 (BM5) 5-Pin SOT23 (YM5) Pin Description Pin Number Pin Name Pin Function 1 VCC Chip Supply: +2.2V to +16V. 2 GND Ground: Return for internal circuitry and internal MOSFET (switch) source. 3 SW Switch Node (Input): Internal MOSFET drain; 22V maximum. 4 FB Feedback (Input): Output voltage sense node. 5 EN Shutdown: Device shuts down to 0.1µA typical supply current. October 2007 2 M9999-102507 Micrel, Inc. MIC2142 Absolute Maximum Ratings(1) Operating Ratings(2) Supply Voltage (VCC)......................................................18V Switch Voltage (VSW)......................................................24V Enable Pin Voltage (VEN)(3) .............................................18V Feedback Voltage (VFB) Adjustable Version.....................................................8V Ambient Storage Temperature (Ts) ...........–65°C to +150°C ESD Rating(4) Supply Voltage (VCC)......................................... 2.2V to 16V Enable Pin Voltage (VEN)(3)................................... 0V to 16V Switch Voltage (VSW)......................................................22V Ambient Temperature (TA) .......................... –40°C to +85°C Junction Temperature Range (TJ)............. –40°C to +125°C Package Thermal Impedance SOT23-5 (θJA) ..................................................220°C/W Electrical Characteristics VCC = 3.6V; VOUT = 5V; IOUT = 200mA; TA = 25°C, bold values indicate –40°C< TJ < +125°C, unless noted. Parameter Condition Min Input Voltage Quiescent Current Feedback Voltage (VFB) 2.2 Enable Input Voltage Max Units 16 V µA VEN = ON , VFB = 2.2V (adjustable) 85 125 VEN = ON , VOUT(NOMINAL) + 1V (MIC2142-5.0) 85 125 µA VEN = OFF (shutdown) 0.1 2 µA 1.28 1.306 V (±2%) 1.254 (±3%) 1.241 Comparator Hysteresis Feedback Input Bias Current, Note 5 Typ adjustable fixed VIH (turn on) 0.6VCC VIL (turn off) Enable Input Current –1 1.312 V 18 mV 30 nA 20 µA 0.55VCC V 1.1 0.8 V 0.01 1 µA Load Regulation 200µA ≤ IOUT ≤ 20mA 0.2 %VOUT Line Regulation 2.2V ≤ VCC ≤ 16V; IOUT = 4mA (adjustable) 0.25 %/V 2.2V ≤ VCC ≤ 4.5V; IOUT = 4mA (MIC2142-5.0) 0.25 %/V SW on Resistance ISW = 100mA, VCC = 2.5V Switch Leakage Current VEN = OFF, VSW = 12V 5 Ω 0.05 1 µA Oscillator Frequency 295 330 365 kHz Duty Cycle 50 57 65 % Notes: 1. Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the device outside of its operating ratings. The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(Max), the junction-to-ambient thermal resistance, θJA, and the ambient temperature, TA. The maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. The θJA of the power SOT23-5 is 220°C/W mounted on a PC board. 2. The device is not guaranteed to function outside its operating rating. 3. VEN must be ≤ VIN. 4. Devices are ESD sensitive. Handling precautions recommended. 5. The maximum suggested value of the programming resistor, whose series resistance is measured from feedback to ground, is 124kΩ. Use of larger resistor values can cause errors in the output voltage due to the feedback input bias current. October 2007 3 M9999-102507 Micrel, Inc. MIC2142 Typical Characteristics Quiescent Current vs. Input Voltage 250 200 150 100 50 2 IL = 2mA L = 220µH 200 Oscillator Characteristics vs. Input Voltage Frequency 250 0.65 0.60 0.55 200 Duty Cycle 0.50 100 V = 15V O 0.45 50 IO = 100µA L= 220µH 0 0.40 0 2 4 6 8 10 12 14 INPUT VOLTAGE (V) 84 14 MIC2142 Load Regulation VOUT 14 12 10 L = 22µH 8 VIN = 5V 6 4 VREF 2 5 10 15 20 25 30 OUTPUT CURRENT (mA) Quiescent Current vs. Temperature 80 78 76 74 72 VIN = 3.6V 70 -50 -30 -10 10 30 50 70 90 110 TEMPERATURE °C) ( Frequency vs. Temperature 335 FREQUENCY (kHz) 6 8 10 12 INPUT VOLTAGE (V) 82 340 330 325 320 315 310 305 300 295 -50 -30 -10 10 30 50 70 90 110 TEMPERATURE °C) ( October 2007 4 0 0 4 6 8 10 12 14 INPUT VOLTAGE (V) QUIESCENT CURRENT (µA) 2 DUTY CYCLE 0 0 150 14.5 OUTPUT VOLTAGE (V) 400 300 15 16 800 VOUT = 15V IL = 2mA L = 220µH 14 2 IL = 7mA L = 22 H 600 Line Regulation IL = 7mA L = 22 H 15.5 Output Ripple vs. Input Voltage 1000 350 16 4 6 8 10 12 14 16 INPUT VOLTAGE (V) 1200 OUTPUT RIPPLE (mV) OUTPUT VOLTAGE (V) VOUT = 5V 300 0 0 FREQUENCY (kHz) 16.5 4 OSCILLATOR CHARACTERISTICS QUIESCENT CURENT (µA) 350 3.5 Timing Characteristics Over Temperature 3.0 T (µsec) 2.5 2.0 1.5 t ON (µsec) 1.0 0.5 Duty Cycle 0 -50 -30 -10 10 30 50 70 90 110 TEMPERATURE °C) ( M9999-102507 Micrel, Inc. MIC2142 Typical Characteristics (cont.) 6 VCC=3.3V RDS(O N) (Ω) 5 4 3 VCC = 4.5V 2 1 0 -50 -30 -10 10 30 50 70 90 110 TEMPERATURE °C) ( October 2007 DUTY CYCLE (%) 7 Timing Characteristics Over Temperature RDS(ON) vs. Temperature 0.6 0.58 0.56 0.54 0.52 0.5 0.48 0.46 0.44 0.42 0.4 -50 -30 -10 10 30 50 70 90 110 TEMPERATURE °C) ( 5 M9999-102507 Micrel, Inc. MIC2142 Functional Diagram SW VCC Bandgap Reference 1.265V Oscillator 330kHz FIXED DUTY CYCLE EN Shutdown FB MIC2142 GND Functional Description This MIC2142 is a fixed duty cycle, constant frequency, gated oscillator, micropower, switch-mode power supply controller. Quiescent current for the MIC2142 is only 85µA in the switch off state, and since a MOSFET output switch is used, additional switch drive current is minimized. Efficiencies above 85% throughout most operating conditions can be realized. A functional block diagram is shown above and typical schematic is shown on page 1. Regulation is performed by a hysteretic comparator, which regulates the output voltage by gating the internal oscillator. The internal oscillator operates at a fixed 57% duty cycle and 330kHz frequency. For the fixed output versions, the output is divided down internally and then compared to the internal VREF input. An external resistive divider is use for the adjustable version. October 2007 The comparator has hysteresis built into it, which determines the amount of low frequency ripple that will be present on the output. Once the feedback input to the comparator exceeds the control voltage by 18mV, the high frequency oscillator drive is removed from the output switch. As the feedback input to the comparator returns to the reference voltage level, the comparator is reset and the high frequency oscillator is again gated to the output switch. The 18mV of hysteresis seen at the comparator will be multiplied by the ratio of the output voltage to the reference voltage. For a five volt output this ratio would be 4, corresponding to a ripple voltage of 72mV at the output. The maximum output voltage is limited by the voltage capability of the output switch. Output voltages up to 22V can be achieved with a standard boost circuit. Higher output voltages can be realized with a flyback configuration. 6 M9999-102507 Micrel, Inc. MIC2142 Application Information Pre-designed circuit information is at the end of this section. Component Selection Resistive Divider (Adjustable Version) The external resistive divider should divide the output volt-age down to the nominal reference voltage. Current drawn through this resistor string should be limited in order to limit the effect on the overall efficiency. The maximum value of the resistor string is limited by the feedback input bias current and the potential for noise being coupled into the feedback pin. A resistor string on the order of 2MΩ limits the additional load on the output to 20µA for a 20V output. In addition, the feedback input bias current error would add a nominal 60mV error to the expected output. Equation 1 can be used for determining the values for R2 and R1. (1) VOUT IO(max) = (3) IPK = (VIN(min) t ON ) 2 2L MAX TS × 1 VO − VIN(min) eff t ON(max)VIN(max) L MIN Table 1 lists common inductors suitable for most applications. Due to the internal transistor peak current limitation at low input voltages, inductor values less than 10µH are not recommended. Table 6 lists minimum inductor sizes versus input and output voltage. In lowcost, low-peak-current applications, RF-type leaded inductors may sufficient. All inductors listed in Table 5 can be found within the selection of CR32- or LQH4Cseries inductors from either Sumida or MuRata. ⎛ R1 + R2 ⎞ =⎜ ⎟ VREF ⎝ R1 ⎠ Boost Inductor Maximum power is delivered to the load when the oscillator is gated on 100% of the time. Total output power and circuit efficiency must be considered when determining the maximum inductor value. The largest inductor possible is preferable in order to minimize the peak current and output ripple. Efficiency can vary from 80% to 90% depending upon input voltage, output voltage, load current, inductor, and output diode. Equation 2 solves for the output current capability for a given inductor value and expected efficiency. Figures 7 through 12 show estimates for maximum output current assuming the minimum duty and maximum frequency and 80% efficiency. To determine the necessary inductance; find the intersection between the output voltage and current, and then select the value of the inductor curve just above the intersection. If the efficiency is expected to be different than the 85% used for the graph, Equation 2 can then be used to better determine the maximum output capability. The peak inductor/switch current can be calculated from Equation 3 or read from the graph in Figure 13. The peak current shown in the graph in Figure 13 is derived assuming a max duty cycle and a minimum frequency. The selected inductor and diode peak current capability must be greater than this. The peak current seen by the inductor is calculated at the maximum input voltage. A wide ranging input voltage will result in a higher worst case peak current in the inductor than a narrow input range. October 2007 (2) Manufacturer Series Device Type MuRata LC4/C3/C1HQ surface mount Sumida CR32 surface mount J.W. Miller 78F axial leaded Coilcraft 90 axial leaded Table 1. Inductor Examples Boost Output Diode Speed, forward voltage, and reverse current are very important in selecting the output diode. In the boost configuration the average diode current is the same as the average load current and the peak is the same as the inductor and switch current. The peak current is the same as the peak inductor current and can be derived from Equation 3 or the graph in Figure 13. Care must be taken to make sure that the peak current is evaluated at the maximum input voltage. The BAT54 and BAT85 series are low current Shottky diodes available from “On Semiconductor” and “Phillips” respectively. They are suitable for peak repetitive currents of 300mA or less with good reverse current characteristics. For applications that are cost driven, the 1N4148 or equivalent will provide sufficient switching speed with greater forward drop and reduced cost. Other acceptable diodes are On Semiconductor’s MBR0530 or Vishay’s B0530, although they can have reverse currents that exceed 1 mA at very high junction temperatures. Table 2 summarizes some typical performance characteristics of various suitable diodes. 7 M9999-102507 Micrel, Inc. MIC2142 t ON(min) = 75°C VFWD at 100mA 25°C VFWD at 100mA Room Temp. Leakage at 15V 75°C Leakage at 15V Package MBR0530 0.275V 0.325V 2.5µA 90µA SOD123 SMT 1N4148 0.6V (175°C) 0.95V 25nA (20V) 0.2µA (20V) leaded and SMT BAT54 0.4V (85°C) 0.45V 10nA (25V) 1µA (20V) SMT BAT85 0.54V (85°C) 0.56V 0.4µA 2µA (85°C) DO-34 leaded Diode L max = VIN(min) 2 × t ON(min) 2 IO(max) × 2 × TS(min) Series Type Package GRM ceramic Y5V surface mount Vishay 594 tantalum surface mount Panasonic M-series Electrolytic leaded t ON(max) = Ipeak = Design Example Given a design requirement of 12V output and 1mA load with a minimum input voltage of 2.5V, Equation 2 can be used to calculate to maximum inductance or it can be read from the graph in Figure 7. Once the maximum inductance has been determined the peak current can be determined using Equation 3 or the graph in Figure 13. VOUT = 12V IOUT = 5mA VIN = 2.5V to 4.7V Fmax = 360kHz η = 0.8 = efficiency Dnom = 0.55 TS(min) = Fmax VO − VIN(min) η 1.1 × D nom 1.1 × 0.55 = = 2µsec Fmin 300kHz t ON(max) × VIN(max) L min 2.0 µsec × 4.7V = 270mA 35 µH = Bootstrap Configuration For input voltages below 4.5V the bootstrap configuration can increase the output power capability of the MIC2142. Figure 2 shows the bootstrap configuration where the output voltage is used to bias the MIC2142. This improves the power capability of the MIC2142 by increasing the gate drive volt-age hence the peak current capability of the internal switch. This allows the use of a smaller inductor which increases the output power capability. Table 4 also summarizes the various configurations and power capabilities using the booststrap configuration. This bootstrap configuration is limited to output voltage of 16V or less. Figure 1 shows how a resistor (R3) can be added to reduce the ripple seen at the VCC pin when in the bootstrap configuration. Reducing the ripple at the VCC pin can improve output ripple in some applications. Table 3. Capacitor Examples 1 1 2.5 2 × 1.53 µsec 2 1 × = 42 µH 5mA × 2 × 2.78 µsec 12 − 2.5 0.8 Select 39µH ±10%. Output Capacitor Due to the limited availability of tantalum capacitors, ceramic capacitors and inexpensive electrolyics may be preferred. Selection of the capacitor value will depend upon the peak inductor current and inductor size. MuRata offers the GRM series with up to 10µF @ 25V with a Y5V temperature coefficient in a 1210 surface mount package. Low cost applications can use the Mseries leaded electrolytic capacitor from Panasonic. In general, ceramic, electrolytic, or tantalum values ranging from 1µF to 22µF can be used for the output capacitor. MuRata × L max = Table 2. Diode Examples Manufacturer D nom 0.55 = = 1.53 µsec fmax 360kHz +3.0V to +4.2V VIN L1 33µH CR1 MBR0530 R3 100 C2 10µF 5 2 EN VCC 1 R2 36.5k C3 270pF R1 12.4k U1 MIC2142 FB SW 3 4 GND +5V @80mA C1 22µF C4 1F 1 = = 2.78 µsec 360kHz GND GND Figure 1. Bootstrap VCC with VCC Low Pass Filter October 2007 8 M9999-102507 Micrel, Inc. MIC2142 L1 47µH VIN CR1 MBR0530 +5V @16mA R2 36.5k R1 12.4k U1 MIC2142 SW 3 4 FB C2 10µF 5 GND 2 EN VCC 1 C3 270pF C1 22µF GND GND Figure 2. Bootstrap Configuration For additional pre-designed circuits, see Table 4. L1 10µH CR1 MBR0530 VIN +15V @15mA CR5 LWT673 CR7 LWT673 CR6 LWT673 U1 MIC2142 FB SW 3 4 (from controller) PWM GND 2 EN VCC 1 C2 10µF 5 C1 1µF 25V Rprogram 82 GND GND Figure 3. Series White LED Driver with PWM Dimming Control L1 10µH CR1 MBR0530 VIN +15V @15mA CR5 LWT673 CR7 LWT673 CR6 LWT673 U1 MIC2142 FB SW 3 4 C2 10µF SHTDWN 5 GND 2 EN VCC 1 C1 1µF 25V Rprogram 82 GND DAC GND R4 R3 Figure 4. Series White LED Driver with Analog Dimming Control October 2007 9 M9999-102507 Micrel, Inc. MIC2142 Figure 5. Parallel White LED Driver with Analog Dimming Control VIN L1 10µH CR1 BAT54HT1 +20V @0.5mA R2 1.8M C2 10µF U1 MIC2142 FB SW 3 R1 120k 4 5 GND 2 EN VCC 1 C1 1µF 25V C1 1µF 25V VINRTN GND Figure 6. Handheld LCD Supply October 2007 10 M9999-102507 Micrel, Inc. MIC2142 VIN(min) 2.5V VIN(max) 3.0V VOUT 3.3V 2.5V 4.5V 5V 11.5 boot strapped boot strapped 12 2.5 4.7 2.5 14.5 4.7 boot strapped boot strapped 15 2.5 2.5 3.0 4.7 4.7 4.7 3.0 3.0 3.0 3.0 3.0 5.0 8.5 4.7 4.7 14.5 4.7 4.7 4.7 8.5 boot strapped boot strapped 20 20 5 boot strapped boot strapped 9 boot strapped boot strapped 15 boot strapped boot strapped 20 9 5.0 11.5 12 5.0 14.5 15 5.0 9 9 8.0 11.5 20 12 9 14 15 9 14 20 12 14 15 12 14 20 IOUT(max) 40mA 23mA 10mA 16.5mA 7.8mA 51 77 1.8 2.25 15 22 3.7 1.7 17.4 8 2.7 1.5 40 70 100 15 28 40 7.8 14 21 5.6 70 23 10 43 14 6 30 10 30 8 118 66 30 70 40 18 20 10 6 156 71 27 35 L1 47µH 85µH 180µH 47µH 100µH 15 10 47 100 15 10 47 100 10 22 47 82 33 18 12 33 18 12 33 18 12 33 27 82 180 27 82 180 27 82 27 68 56 100 220 56 100 220 120 220 390 68 150 390 150 IPK @ VIN(max) 129mA 74mA 34VmA 193mA 91mA 605 908 493 232 632 950 622 292 950 430 202 110 287 525 800 520 525 800 886 525 800 287 635 209 95 860 283 129 1083 357 672 237 414 232 105 504 282 128 235 128 72 415 182 72 188 CR1 BAT54 BAT54 BAT54 BAT54 BAT54 MBR0530 MBR MBR BAT MBR MBR MBR BAT MBR MBR BAT BAT BAT MBR MBR MBR MBR MBR MBR MBR MBR BAT MBR BAT BAT MBR BAT BAT MBR MBR MBR BAT MBR BAT BAT MBR BAT BAT BAT BAT BAT MBR BAT BAT BAT Table 4. Typical Maximum Power Configuration October 2007 11 M9999-102507 Micrel, Inc. MIC2142 VIN 3.3V±5% 5V±5% 12V±5% 15V±5% VOUT 5V 9V 12V 15 20 9V 12V 15V 20 15V 20V 20V IOUT 70mA 30mA 20mA 15mA 6mA 70mA 40mA 30mA 8mA 158 35 50 L1 18µH 18µH 18µH 18µH 33µH 27µH 27µH 27µH 68µH 68 150 220 CR1 MBR0530 MBR0530 MBR0530 MBR0530 BAT54 MBR0530 MBR0530 MBR0530 BAT54 MBR0530 BAT54 BAT54 IPEAK 400 400 400 400 214 370 370 370 148 350 160 1140 Configuration Bootstrap Bootstrap Bootstrap Bootstrap Table 5. Typical Maximum Power Configurations for Regulated Inputs VIN (V) 2.5 3 3.5 4 5 6 7 8 9 10 11 12 13 14 15 16 VOUT = 16V to 22V 85°C LMIN (µH) 47 33 47 56 68 82 100 100 120 150 150 150 180 180 220 220 VOUT < 16V (bootstapped) 85°C LMIN (µH) 47 (15) 33 (18) 27 (22) 27 (22) 27 33 39 47 56 56 68 68 82 82 82 100 VOUT < 16V (bootstapped) 40°C LMIN (µH) 47 (10) 33 (12) 27 (15) 22 (18) 22 22 27 33 33 39 47 47 56 56 56 68 Table 6. Minimum Inductance Manufacturer MuRata Sumida Coilcraft J.W. Miller Micrel Vishay Panasonic Web Address www.murata.com www.sumida.com www.coilcraft.com www.jwmiller.com www.micre.com www.vishay.com www.panasonic.com Table 7. Component Supplier Websites October 2007 12 M9999-102507 Micrel, Inc. MIC2142 Inductor Selection Guides Figure 7. Inductor Selection for VIN = 2.5V October 2007 Figure 8. Inductor Selection for VIN = 3.0V 13 M9999-102507 Micrel, Inc. MIC2142 Figure 9. Inductor Selection for VIN = 5V October 2007 Figure 10. Inductor Selection for VIN = 9V 14 M9999-102507 Micrel, Inc. MIC2142 IN Figure 11. Inductor Selection for VIN = 12V October 2007 Figure 8. Inductor Selection for VIN = 15V 15 M9999-102507 Micrel, Inc. MIC2142 Figure 13. Peak Inductor Current vs. Input Voltage October 2007 16 M9999-102507 Micrel, Inc. MIC2142 Package Information 5-Pin SOT23 (M5) MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2000 Micrel, Incorporated. October 2007 17 M9999-102507