MIC2172/3172 SEPIC Evaluation Board 100kHz Switching Regulator St

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MIC2172/3172 SEPIC Evaluation Board 100kHz Switching Regulator St

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MIC2172/3172 SEPIC Evaluation Board
MIC2172/3172 SEPIC Evaluation Board
100kHz Switching Regulator Steve Chenetz
General Description
This evaluation board demonstrates MIC3172 MIC2172 used SEPIC converter topology. SEPIC (single-ended primary inductance converter) topology provides regulated output voltage from input that range from greater than less than output voltage. also capacitively decouples input from output, completely shutting down output (zero volts) when converter stops switching. entire circuit takes less than board space while producing 1.5W output power. switching frequency 100kHz. efficiency full load better than 65%. MIC3172 features quiescent current shutdown pin. MIC2172 features sync external synchronization. Requirements SEPIC evaluation board requires input power source, which should able supply minimum 0.5A. output loaded with resistive active load. active load constant current constant resistance mode. Precautions evaluation board does have input reverse polarity protection. Applying negative voltage terminal (with respect ground) permanently damage components board.
maximum input voltage board 16V, limited input capacitor's voltage rating. Exceeding this voltage extended period time will damage capacitors. tantalum output capacitors rated 10V. exceed rating these capacitors. Circuit Operation schematic MIC3172/MIC2172 SEPIC evaluation board shown Figure MIC3172 switching regulator combines switching transistor, control circuitry, reference single package, which provides switching output voltage regulation. When MIC3172 switching transistor turns current flowing into switch equal currents (IL1 IL2). Energy stored both inductors. voltage across equal (neglecting switch voltage) voltage anode -VIN. During this time diode, sees reverse voltage VOUT. When switching transistor turns off, currents flowing inductors forces voltage across each inductor reverse polarity. voltage across inductors rise until conducts clamps inductor voltage VOUT VD1. energy inductors discharged into output. peak diode current equal IL2. provide compensation stabilize voltage control loop. create zero feedback loop compensate pole formed output capacitance (C3, output resistance. creates pole that compensates zero caused output capacitance output capacitor ESR.
10µF
33µH
10µF,
MBRM140
VOUT 220µF 220µF 0.1µF
Enable
MIC3172 COMP SGND PGND1 PGND2
33µH
3.01k
SYNC 33pF open 4.75k 0.01µF
1.82k 3.3V
1.62k 3.6V
5.0V
6.0V
3300pF
J1a*
CMPD6263 other voltages Note Remove switch when using MIC2172 (sync input). Note used with MIC3172 (enable input).
Single-Ended Primary Inductance Converter
Micrel, Inc. 1849 Fortune Drive Jose, 95131 (408) 944-0800 (408) 944-0970 http://www.micrel.com
August 1998
MIC2172/3172 SEPIC Evaluation Board
MIC2172/3172 SEPIC Evaluation Board
MIC3172 (Enable Input) board comes assembled with MIC3172 converter which enable function. Switch used enable (pin high) disable (pin low) converter. MIC2172 (Sync Input) sync function required, control replaced with MIC2172BM. enable switch, must removed proper operation. capacitively couples sync signal Diode prevents sync signal from going more than diode drop below ground. 0805-size resistor added location adjust switching frequency. Refer MIC2172 data sheet additional information using sync input. Output Voltage Configuration four standard voltages selected placing shorting jumper across corresponding pins header
Open resistor location accepts 0805-size resistor nonstandard output voltage. desired output voltage, calculate value resistor using:
1.24R1 VOUT 1.24
Output Capacitors Both output capacitance capacitor's (equivalent series resistance) affect output ripple. primary contributor output ripple. impedance tantalum capacitors provided minimize effective reduce output ripple voltage. While capacitors necessary higher output currents, only capacitor necessary when output current less than 100mA when ripple voltage critical.
Bill Materials
Item JP1A-E 2551-2-00-01-00-00-07-0 Mill-Max Part Number MIC3172BM C23Y5V1C106ZP TPSE227M010R0060 08053C103MATMA 08053C332MATMA 08055A330MATMA 08055A104MATMA MBRM140 CMPD6263 CTX33-2P Manufacturer Micrel Tokin Motorola Central Semiconductor Coiltronics Description 100kHz 1.25A switching reg. ceramic tantalum ceramic ceramic ceramic ceramic, Schottky signal Schottky inductor 0805-size resistor 0805-size resistor 0805-size resistor 0805-size resistor 0805-size resistor 0805-size resistor 0805-size resistor 0805-size resistor toggle switch SPDT jumper turret pins 3.01k, open resistor location 1.82k, 1.62k, 1.00k, 787, 4.75k, open resistor location 10µF, 220µF, 0.01µF 3300pF 33pF 0.1µF Value Quantity
MIC2172/3172 SEPIC Evaluation Board
August 1998
MIC2172/3172 SEPIC Evaluation Board
Component Side
Solder Side
Component-Side Silk Screen
Solder-Side Silk Screen
August 1998
MIC2172/3172 SEPIC Evaluation Board
MIC2172/3172 SEPIC Evaluation Board
MICREL INC. 1849 FORTUNE DRIVE JOSE, 95131
(408) 944-0800
(408) 944-0970
http://www.micrel.com
This information believed accurate reliable, however responsibility assumed Micrel infringement patents other rights third parties resulting from use. license granted implication otherwise under patent patent right Micrel Inc. 1998 Micrel Incorporated
MIC2172/3172 SEPIC Evaluation Board
August 1998

MIC2172/3172 SEPIC Evaluation Board 100kHz Switching Regulator St

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