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MIC2142 Micropower Boost Converter - 17 Pages

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Catalogue excerpts

MIC2142 Micropower Boost Converter 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 General Description The MIC2142 is a micropower boost switching regulator housed in a SOT23-5 package. The input voltage range is between 2.2V to 16V, making the device suitable for onecell Li Ion and 3 to 4-cell alkaline/NiCad/NiMH applications. The output voltage of the MIC2142 can be adjusted up to 22V. The MIC2142 is well suited for portable, space-sensitive applications. It features a low quiescent current of 85ìA, and a typical shutdown current of 0.1ìA. It’s 330kHz operation allows small surface mount external components to be used. The MIC2142 is capable of efficiencies over 85% in a small board area. The MIC2142 can be configured to efficiently power a variety of loads. It is capable of providing a few mA output for supplying low power bias voltages; it is also capable of 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. Features • 2.2V to 16V input voltage • Up to 22V output voltage • 330kHz switching frequency • 0.1ìA shutdown current • 85ìA quiescent current • Implements low-power boost, SEPIC, or flyback • SOT23-5 package Applications • LCD bias supply • White LED driver • 12V Flash memory supply • Local 3V to 5V conversion ___________________________________________________________________________________________________________ Typical Application R2 365k R1 124k +5V @60mA 2.8V to 4.7V VIN L1 33ìH D1 MIC2142 5 3 4 2 1 VCC SW FB EN GND CIN 10ìF COUT 22ìF 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0 10 20 30 40 50 60 70 EFFICIENCY (%) OUTPUT CURRENT (mA) Efficiency vs. Output Current VIN = 4.2V VIN = 3.0V Typical Configuration Efficiency vs. Output Current

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Micrel, Inc. MIC2142 October 2007 2 M9999-102507 Ordering Information Part Number Marking* Standard Pb-Free Standard Pb-Free Voltage Ambient Temperature Range Package MIC2142BM5 MIC2142YM5 SBAA SBAA 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....

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Micrel, Inc. MIC2142 October 2007 6 M9999-102507 Functional Diagram FIXED DUTY CYCLE FB EN VCC 1.265V GND SW Oscillator MIC2142 Bandgap Reference Shutdown 330kHz 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 85ìA 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...

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Micrel, Inc. MIC2142 October 2007 7 M9999-102507 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...

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Micrel, Inc. MIC2142 October 2007 8 M9999-102507 Diode 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 2.5ìA 90ìA SOD123 SMT 1N4148 0.6V (175°C) 0.95V 25nA (20V) 0.2ìA (20V) leaded and SMT BAT54 0.4V (85°C) 0.45V 10nA (25V) 1ìA (20V) SMT BAT85 0.54V (85°C) 0.56V 0.4ìA 2ìA (85°C) DO-34 leaded Table 2. Diode Examples 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...

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Micrel, Inc. MIC2142 October 2007 13 M9999-102507 Inductor Selection Guides Figure 7. Inductor Selection for VIN = 2.5V Figure 8. Inductor Selection for VIN = 3.0V

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Micrel, Inc. MIC2142 October 2007 14 M9999-102507 Figure 9. Inductor Selection for VIN = 5V Figure 10. Inductor Selection for VIN = 9V

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Micrel, Inc. MIC2142 October 2007 15 M9999-102507 IN Figure 11. Inductor Selection for VIN = 12V Figure 8. Inductor Selection for VIN = 15V

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Micrel, Inc. MIC2142 October 2007 16 M9999-102507 Figure 13. Peak Inductor Current vs. Input Voltage

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Micrel, Inc. MIC2142 October 2007 17 M9999-102507 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...

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