MIC4576 Micrel, Inc. MIC4576 200kHz Simple 3A Buck Regulator General Description Features The MIC4576 is a series of easy to use fixed and adjustable BiCMOS step-down (buck) switch-mode voltage regulators. The 200kHz MIC4576 duplicates the pinout and function of the 52kHz LM2576. The higher switching frequency may allow up to a 2:1 reduction in output filter inductor size. • 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 3A switch current • Wide 4V to 36V input voltage range • Wide 1.23V to 33V output voltage range • Requires minimum external components • < 200µA typical shutdown mode • 75% efficiency (adjustable version > 75% typical) • Standard inductors are 25% of typical LM2576 values • Thermal shutdown • Overcurrent protection • 100% electrical thermal limit burn-in The MIC4576 is available in 3.3V, and 5V fixed output versions or a 1.23V to 33V adjustable output version. Both versions are capable of driving a 3A 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 200µA standby current. The regulator performs cycle-by-cycle current limiting and thermal shutdown for protection under fault conditions. Applications • • • • • • • This series of simple switch-mode regulators requires a minimum number of external components and can operate using a standard series of inductors. Frequency compensation is provided internally. The MIC4576 is available in TO-220 (T) and TO-263 (U) packages for the industrial temperature range. 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 to 3.3V for Intel Pentium™ and similar microprocessors Typical Applications 5 Shutdown Enable 8V to 36V C1 470µF 63V 1 SHDN SW MIC4576-5.0WT VIN FB GND L1 2 5V/3A 33µH 4 D1 MBR360 3 C2 1000µF 16V Fixed Regulator Shutdown Enable 16V to 36V C1 470µF 63V 5 1 SHDN SW MIC4576WT FB VIN GND 2 L1 68µH 4 MBR360 3 12V/3A R2 13.0k 1% R1 1.50k 1% C2 1000µF 16V Adjustable Regulator Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com March 2006 1 MIC4576 MIC4576 Micrel, Inc. Ordering Information Standard Part Number RoHS Compliant Part Number* Voltage Temperature Range Package MIC4576-3.3BT MIC4576-3.3WT 3.3V –40ºC to +85ºC TO-220-5 MIC4576-5.0BT MIC4576-5.0WT 5.0V –40ºC to +85ºC TO-220-5 MIC4576BT MIC4576WT ADJ. –40ºC to +85ºC TO-220-5 MIC4576-3.3BU MIC4576-3.3WU 3.3V –40ºC to +85ºC TO-263-5 MIC4576-5.0BU MIC4576-5.0WU 5.0V –40ºC to +85ºC TO-263-5 MIC4576BU MIC4576WU ADJ. –40ºC to +85ºC TO-263-5 * RoHS compliant with "high-melting solder" exemption. Pin Configuration TAB 5 4 3 2 1 SHDN FB GND SW VIN 5-Pin TO-220 (T) TAB 5 4 3 2 1 SHDN FB GND SW VIN 5-Pin TO-263 (U) Pin Description Pin Number Pin Name 1 VIN MIC4576 2 SW 3, TAB GND 4 FB 5 SHDN Pin Function Supply Voltage (Input): Unregulated +4V to +36V supply voltage. Switch (Output): Emitter of NPN output switch. Connect to external storage inductor and Shottky diode. Ground 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. Shutdown (Input): Logic low enables regulator. Logic high (> 2.4V) shuts down regulator. 2 March 2006 MIC4576 Micrel, Inc. Absolute Maximum Ratings Operating Ratings Supply Voltage (VIN) .................................................... +40V Shutdown Voltage (VSHDN)............................–0.3V to +36V Output Switch (VSW), Steady State ............................... –1V Feedback Voltage (VFB) [Adjustable] ......................... +3.8V Storage Temperature ................................ –65°C to +150°C Supply Voltage (VIN) .................................................... +36V Junction Temperature .............................................. +150°C Package Thermal Resistance TO-220, TO-263 (θJA) ......................................... 65°C/W TO-220, TO-263 (θJC) ............................................ 2°C/W Electrical Characteristics VIN = 12V; ILOAD = 500mA; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +85°C; unless noted. Parameter Condition Min Typ Max Units 1.217 1.230 1.243 V 1.193 1.180 1.230 1.267 1.280 V V 77 % 90 95 % MIC4576 [Adjustable] Feedback Voltage Feedback Voltage 8V ≤ VIN ≤ 36V, 0.5A ≤ ILOAD ≤ 3A Efficiency ILOAD = 3A, Note 1 Maximum Duty Cycle (On) VFB = 1.0V Output Leakage Current VIN = 36V, VFB = 1.5V output = 0V output = –1V Quiescent Current VFB = 1.5V Feedback Bias Current 0 7.5 2 35 mA mA 5 10 mA 50 100 500 nA nA 3.234 3.3 3.366 V 3.168 3.135 3.3 3.432 3.465 V V 72 % 90 95 % MIC4576-3.3 Output Voltage Output Voltage 6V ≤ VIN ≤ 36V, 0.5A ≤ ILOAD ≤ 3A Efficiency ILOAD = 3A Maximum Duty Cycle (On) VFB = 2.5V Output Leakage Current VIN = 36V, VFB = 4.0V output = 0V output = –1V Quiescent Current VFB = 4.0V MIC4576-5.0 Output Voltage Output Voltage 8V ≤ VIN ≤ 36V, 0.5A ≤ ILOAD ≤ 3A Efficiency ILOAD = 3A Maximum Duty Cycle (On) VFB = 4.0V Output Leakage Current VIN = 36V, VFB = 6.0V output = 0V output = –1V Quiescent Current VFB = 6.0V March 2006 0 7.5 2 35 mA mA 5 10 mA 4.900 5.0 5.100 V 4.800 4.750 5.0 5.200 5.250 V V 90 3 77 % 95 % 0 7.5 2 35 mA mA 5 10 mA MIC4576 MIC4576 Parameter Micrel, Inc. Condition Min Typ Max Units 180 200 220 kHz 1.7 2.3 2.5 V V 5.2 7.9 8.5 A A 50 200 µA MIC4576 / -3.3 / -5.0 Oscillator Frequency Saturation Voltage IOUT = 3A Current Limit peak current, tON ≤ 3µs; VFB = 0V Standby Quiescent Current VSHDN = 5V (regulator off), VFB = 0V SHDN Input Logic Level VOUT = 0V (regulator off) 4.2 3.5 2.2 2.4 VOUT = 3.3V or 5V (regulator on) SHDN Input Current VSHDN = 5V (regulator off) VSHDN = 0V (regulator on) –10 1.4 V V 1.2 1.0 0.8 V V 4 0.01 30 10 µA µA General Note: Devices are ESD protected, however, handling precautions are recommended. Note 1: VOUT = 5V MIC4576 4 March 2006 MIC4576 Micrel, Inc. Block Diagrams +36V max. VIN Shutdown Enable SHDN CIN Internal Regulator Thermal Shutdown 200kHz Oscillator Driver Comparator Error Amp. Current Limit 3A Switch L1 SW VOUT D1 COUT 1.23V Bandgap R1 FB R2 MIC4576-x.x GND Block Diagram with External Components Fixed Step-Down Regulator +36V max. VIN Shutdown Enable SHDN CIN Internal Regulator Thermal Shutdown 200kHz Oscillator Comparator Error Amp. Current Limit Driver 3A Switch L1 SW VOUT D1 1.23V Bandgap COUT R1 FB MIC4576 [Adjustable] R2 GND Block Diagram with External Components Adjustable Step-Down Regulator March 2006 5 MIC4576 MIC4576 Micrel, Inc. Functional Description The MIC4576 is a variable duty cycle switch-mode regulator with an internal power switch. Refer to the block diagrams. A higher feedback voltage increases the error amplifier output voltage. A higher error amplifier voltage (comparator inverting input) causes the comparator to detect only the peaks of the sawtooth, reducing the duty cycle of the comparator output. A lower feedback voltage increases the duty cycle. Supply Voltage The MIC4576 operates from a +4V to +36V unregulated input. Highest efficiency operation is from a supply voltage around +15V. Output Switching When the internal switch is on, an increasing current flows from the supply VIN, through external storage inductor L1, to output capacitor COUT and the load. Energy is stored in the inductor as the current increases with time. Enable/Shutdown The shutdown (SHDN) input is TTL compatible. Ground the input if unused. A logic-low enables the regulator. A logichigh shuts down the internal regulator which reduces the current to typically 50µA. When the internal switch is turned off, the collapse of the magnetic field in L1 forces current to flow through fast recovery diode D1, charging COUT. Feedback Fixed versions of the regulator have an internal resistive divider from the feedback (FB) pin. Connect FB directly to the output line. Output Capacitor External output capacitor COUT provides stabilization and reduces ripple. Adjustable versions require an external resistive voltage divider from the output voltage to ground, connected from the 1.23V tap to FB. Return Paths During the on portion of the cycle, the output capacitor and load currents return to the supply ground. During the off portion of the cycle, current is being supplied to the output capacitor and load by storage inductor L1, which means that D1 is part of the high-current return path. Duty Cycle Control A fixed-gain error amplifier compares the feedback signal with a 1.23V bandgap voltage reference. The resulting error amplifier output voltage is compared to a 200kHz sawtooth waveform to produce a voltage controlled variable duty cycle output. Applications Information The applications circuits that follow have been constructed and tested. Refer to Application Note 15 for additional information, including efficiency graphs and manufacturer’s addresses and telephone numbers for most circuits. 5 6V to 24V C1 470µF 35V C1 C2 D1 L1 L1 1 SHDN SW MIC4576-3.3BT FB VIN GND 3 Nichicon Nichicon Motorola Coiltronics Bi 2 L1 For a mathematical approach to component selection and circuit design, refer to Application Note 14. 3.3V/3A 5 33µH 4 D1 1N5822 6V to 36V C2 1000µF 16V C1 470µF 63V UPL1V471MPH, ESR = 0.046Ω UPL1C221MPH, ESR = 0.047Ω 1N5822 PL52C-33-1000, DCR = 0.036Ω HM77-30004, DCR = 0.045Ω, Note 2 C1 C2 D1 L1 L1 Figure 1. 6V–24V to 3.3V/3A Buck Converter Through Hole Note 2: 1 SHDN SW MIC4576-3.3BT VIN FB GND 3 Nichicon Nichicon Motorola Coiltronics Bi 2 L1 3.3V/3A 33µH 4 D1 MBR360 C2 1000µF 16V UPL1J471MRH, ESR = 0.039Ω UPL1C102MPH, ESR = 0.047Ω MBR360 PL52C-33-1000 DCR = 0.036 HM77-30004, DCR = 0.045Ω, Note 2 Figure 2. 6V–36V to 3.3V/3A Buck Converter Through Hole Surface-mount component. MIC4576 6 March 2006 MIC4576 Micrel, Inc. 5 8V to 24V C1 470µF 35V 1 SHDN SW MIC4576-5.0BT FB VIN GND C1 Nichicon C2 Nichicon D1 Motorola L1 Coiltronics L1 Bi 3 L1 2 5V/3A 5 33µH 8V to 36V C2 1000µF 16V 4 D1 1N5822 C1 470µF 63V C1 C2 D1 L1 L1 UPL1J471MPH, ESR = 0.046Ω UPL1C102MPH, ESR = 0.047Ω MBR5822 PL52C-33-1000, DCR = 0.036 HM77-30004, DCR = 0.045Ω, Note 2 16V to 36V 1 C1 470µF 63V SHDN VIN SW MIC4576BT GND Nichicon Nichicon Motorola Bi MIC4576-5.0BT VIN FB GND 3 Nichicon Nichicon Motorola Coiltronics Bi FB L1 2 2 L1 5V/3A 33µH 4 D1 MBR360 C2 1000µF 16V UPL1J471MRH, ESR = 0.039Ω UPL1C102MPH, ESR = 0.047Ω MBR360 PLS2C-33-1000, DCR = 0.036 HM77-30004, DCR = 0.045Ω, Note 2 12V/3A 68µH 4 MBR360 3 C1 C2 D1 L1 SW Figure 4. 8V–36V to 5V/3A Buck Converter Through Hole Figure 3. 8V–24V to 5V/3A Buck Converter Through Hole 5 1 SHDN R2 13.0k 1% R1 1.50k 1% C2 1000µF 16V UPL1J471MPH, ESR = 0.039Ω UPL1C102MPH, ESR = 0.047Ω MBR360 HM77-29006, DCR = 0.08Ω Figure 5. 16V–36V to 12V/3A Buck Converter Through Hole U1 5 VIN 8V to 36V 1 SHDN SW MIC4576-5.0BT FB VIN GND R1 0.1Ω L1 2 33µH D1 MBR360 C1 470µF 63V R3 10K C5 0.01µF VIN 8 2 1 3 C3 470µF 63V SHDN FB MIC4576-5.0BT SW VIN GND 3 C1, C3 C2, C4 D1, D2 L1, L2 R1, R2 U3 Nichicon Nichicon Motorola Coiltronics KRL National U3 LM358 4 U2 1 C2 1000µF 16V 4 3 5 VOUT 5V/4A 4 L2 2 33µH D2 MBR360 R2 0.1Ω C4 1000µF 16V UPL1J471MRH, ESR = 0.039Ω UPL1C102MPH, ESR = 0.047Ω MBR360 PL52C-33-1000, DCR = 0.036 SP-1-A1-0R100J LM358 Figure 6. Parallel Switching Regulators Note 2: Surface-mount component. March 2006 7 MIC4576 MIC4576 Micrel, Inc. Package Information 0.150 D ±0.005 (3.81 D ±0.13) 0.177 ±0.008 (4.50 ±0.20) 0.400 ±0.015 (10.16 ±0.38) 0.050 ±0.005 (1.27 ±0.13) 0.108 ±0.005 (2.74 ±0.13) 0.241 ±0.017 (6.12 ±0.43) 0.578 ±0.018 (14.68 ±0.46) SEATING PLANE 7° Typ. 0.550 ±0.010 (13.97 ±0.25) 0.067 ±0.005 (1.70 ±0.127) 0.268 REF (6.81 REF) 0.032 ±0.005 (0.81 ±0.13) 0.018 ±0.008 (0.46 ±0.20) 0.103 ±0.013 (2.62±0.33) Dimensions: inch (mm) 5-Pin TO-220 (T) 0.405 ±0.005 0.065 ±0.010 20°±2° 0.176 ±0.005 0.050 ±0.005 0.060 ±0.005 0.360 ±0.005 0.600 ±0.025 SEATING PLANE 0.004 +0.004 –0.008 0.067 ±0.005 8° MAX 0.032 ±0.003 0.100 ±0.01 0.015 ±0.002 DIM. = INCH 5-Pin TO-263 (U) 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 This information furnished by� Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not� 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 Pr� Micrel for any damages resulting from such use or sale. © 2005 Micrel, Inc. MIC4576 8 March 2006