PDF《MIC4575》

June

2005 1 M9999-062105 MIC4575 Micrel, Inc.

MIC4575 200kHz Simple 1A Buck Regulator General Description The MIC4575 is a series of easy to use fixed and adjustable BiCMOS step-down (buck) switch-mode voltage regulators. The 200kHz MIC4575 duplicates the pinout and function of the 52kHz LM2575. The higher switching frequency may allow up to a 2:1 reduction in output filter inductor size. The MIC4575 is available in 3.3V, and 5V fixed output versions or a 1.23V to 20V adjustable output version. Both versions are capable of driving a 1A load with excellent line and load regulation. The feedback voltage is guaranteed to ±2% tolerance for adjustable versions, and the output voltage is guaranteed to ±3% for fixed versions, within specified voltages and load conditions. The oscillator frequency is guaranteed to ±10%. In shutdown mode, the regulator draws less than 200?A standby current. The regulator performs cycle-by-cycle current limiting and thermal shutdown for protection under fault conditions. This series of simple switch-mode regulators requires a minimum number of external components and can operate using a standard series of inductors. Frequency compensa- tion is provided internally. The MIC4575 is available in TO-220 (T) and TO-263 (U) packages for the industrial temperature range. Typical Applications C1 150?F 35V D1 1N5819 C2 330?F 16V L1 68?H GND FB SW MIC4575-5.0BT SHDN 8V to 24V 5.0V/1A VIN

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1 Shutdown Enable Fixed Regulator C1 22?F 35V MBRS130LT3 C2 330?F 6.3V L1 68?H GND FB MIC4575BU SW SHDN 6V to 24V 3.6V/1A VIN R2 2.37k 1% R1 1.24k 1%

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5 C3 3300pF D1 Shutdown Enable Adjustable Regulator Features ? Fixed 200kHz operation ? 3.3V, 5V, and adjustable output versions ? Voltage over specified line and load conditions: Fixed version: ±3% max. output voltage Adjustable version: ±2% max. feedback voltage ? Guaranteed 1A switch current ? Wide 4V to 24V input voltage range ? Wide 1.23V to 20V output voltage range ? Requires minimum external components ? <

200?A typical shutdown mode ? 75% efficiency (adjustable version >

75% typical) ? Standard inductors and capacitors are 25% of typical LM2575 values. ? Thermal shutdown ? Overcurrent protection ? 100% electrical thermal limit burn-in Applications ? Simple high-efficiency step-down (buck) regulator ? Efficient preregulator for linear regulators ? On-card switching regulators ? Positive-to-negative converter (inverting buck-boost) ? Battery Charger ? Negative boost converter ? Step-down 6V to 3.3V for Intel Pentium? and similar microprocessors Micrel, Inc. ?

2180 Fortune Drive ? San Jose, CA

95131 ? USA ? tel +

1 (408) 944-0800 ? fax +

1 (408) 474-1000 ? http://www.micrel.com MIC4575 Micrel, Inc. M9999-062105

2 June

2005 Ordering Information Part Number Temperature Standard Pb-Free* Voltage Range Package MIC4575-3.3BT MIC4575-3.3WT 3.3V C40°C to +85°C TO-220-5 MIC4575-5.0BT MIC4575-5.0WT 5.0V C40°C to +85°C TO-220-5 MIC4575BT MIC4575WT Adj. C40°C to +85°C TO-220-5 MIC4575-3.3BU MIC4575-3.3WU 3.3V C40°C to +85°C TO-263-5 MIC4575-5.0BU MIC4575-5.0WU 5.0V C40°C to +85°C TO-263-5 MIC4575BU MIC4575WU Adj. C40°C to +85°C TO-263-5 *Pb-Free RoHS compliant with hot-melting solder exemption. Pin Description Pin Number Pin Name Pin Function

1 VIN Supply Voltage (Input): Unregulated +4V to +40V supply voltage.

2 SW Switch (Output): Emitter of NPN output switch. Connect to external storage inductor and Shottky diode. 3, TAB GND Ground

4 FB Feedback (Input): Output voltage feedback to regulator. Connect to output of supply for fixed versions. Connect to 1.23V tap of resistive divider for adjustable versions.