MIC4574 Micrel MIC4574 200kHz Simple 0.5A Buck Voltage Regulator General Description Features The MIC4574 is a series of easy to use fixed and adjustable BiCMOS step-down (buck) switch-mode voltage regulators. The 200kHz MIC4574 duplicates the pinout and function of the 52kHz LM2574. The higher switching frequency may allow up to a 2:1 reduction in output filter inductor size. The MIC4574 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 0.5A load with excellent line and load regulation. • 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 0.5A switch current • Wide 4V to 24V input voltage range • Wide 1.23V to 20V output voltage range • Requires minimum external components • < 200µA typical shutdown mode • 75% efficiency (adjustable version > 75% typ.) • Standard inductors and capacitors are 25% of typical LM2574 values • Thermal shutdown • Overcurrent protection • 100% electrical thermal limit burn-in 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. 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. Applications • • • • • Simple high-efficiency step-down (buck) regulator Efficient preregulator for linear regulators On-card switching regulators Positive-to-negative converter (inverting buck-boost) Isolated flyback converter using minimum external components • Negative boost converter The MIC4574 is available in DIP (N) and SOIC (WM) packages for the industrial temperature range. Typical Applications Shutdown Enable 3 8V to 24V 5 C1 47µF 35V SHDN SW MIC4574-5.0BN FB VIN SGND PGND 2 L1 7 5.0V/0.5A 100µH 1 D1 1N5819 4 C2 220µF 16V Fixed Regulator Shutdown Enable 6V to 24V C1 10µF 35V 5 10 SHDN SW MIC4574BWM FB VIN SGND PGND 4 6 L1 12 100µH 3 D1 3.3V/0.5A R2 2.49k 1% R1 1.50k 1% C3 3300pF C2 330µF 6.3V MBRS130LT3 Adjustable Regulator 4-92 April 1998• MIC4574 Micrel Ordering Information Part Number Voltage Temperature Range Package MIC4574-3.3BN 3.3V –40°C to +85°C 8-pin DIP MIC4574-5.0BN 5.0V –40°C to +85°C 8-pin DIP MIC4574BN MIC4574-3.3BWM MIC4574-5.0BWM MIC4574BWM Adjustable –40°C to +85°C 8-pin DIP 3.3V –40°C to +85°C 14-lead SOIC 5.0V –40°C to +85°C 14-lead SOIC Adjustable –40°C to +85°C 14-lead SOIC Pin Configuration NC 1 14 NC NC 2 13 NC FB 3 12 SW FB 1 8 NC SGND 4 11 NC SGND 2 7 SW SHDN 5 10 VIN SHDN 3 6 NC PGND 6 9 NC PGND 4 5 VIN NC 7 8 NC 8-Pin DIP (N) 14-Lead Wide SOIC (WM) Pin Description Pin Number N Package Pin Number WM Package Pin Name 1 NC Not internally connected. Solder to printed circuit for maximum heat transfer. 2 NC Not internally connected. Solder to printed circuit for maximum heat transfer. 1 3 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. 2 4 SGND Signal Ground 3 5 SHDN Shutdown (Input): Logic low enables regulator. Logic high (> 2.4V) shuts down regulator. 4 6 PGND Power Ground 7 NC Not internally connected. Solder to printed circuit for maximum heat transfer. 8 NC Not internally connected. Solder to printed circuit for maximum heat transfer. 9 NC Not internally connected. Solder to printed circuit for maximum heat transfer. 10 VIN Supply Voltage (Input): Unregulated +4V to +24V supply voltage. 11 NC Not internally connected. Solder to printed circuit for maximum heat transfer. 7 12 SW Switch (Output): Emitter of NPN output switch. Connect to external storage inductor and Shottky diode. 8 13 NC Not internally connected. Solder to printed circuit for maximum heat transfer. 14 NC Not internally connected. Solder to printed circuit for maximum heat transfer. 5 April 1998• Pin Function 4-93 4 MIC4574 Micrel Absolute Maximum Ratings Operating Ratings Supply Voltage (VIN) Note 1 ....................................... +40V Shutdown (VSHDN) ....................................... –0.3V to +36V Output Switch (VSW) steady state ................................. –1V Junction Temperature (TJ) ...................................... +150°C Storage Temperature ............................... –65°C to +150°C Supply Voltage (VIN) ................................................... +24V Package Thermal Resistance θJA Plastic DIP .................................................. 130°C/W θJC SOIC ........................................................... 120°C/W Electrical Characteristics VIN =12V; ILOAD = 100mA; TA = 25°C, bold values indicate –40°C ≤ TA ≤ +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 MIC4574 [Adjustable] Feedback Voltage Feedback Voltage 8V ≤ VIN ≤ 24V, 0.1A ≤ ILOAD ≤ 0.5A Efficiency ILOAD = 0.5A, VOUT = 5V 77 Feedback Bias Current % 50 100 500 nA nA 3.234 3.3 3.366 V 3.168 3.135 3.3 3.432 3.465 V V MIC4574-3.3 Output Voltage Output Voltage 6V ≤ VIN ≤ 24V, 0.1A ≤ ILOAD ≤ 0.5A Efficiency 72 % MIC4574-5.0 Output Voltage Output Voltage 8V ≤ VIN ≤ 24V, 0.1A ≤ ILOAD ≤ 0.5A 4.900 5.0 5.100 V 4.800 4.750 5.0 5.200 5.250 V V Efficiency 77 % MIC4574 / -3.3 / -5.0 Oscillator Frequency 180 Saturation Voltage IOUT = 0.5A Maximum Duty Cycle (On) FB connected to 0V Current Limit Peak Current, tON ≤ 3µs Output Leakage Current VIN = 24V, FB connected to 6V Output = 0V Output = –1V SHDN = 5V (regulator off) SHDN Input Logic Level VOUT = 0V (regulator off) 1 1.3 1.5 V V 0.7 0.65 1.0 1.6 1.8 A A 0 7.5 2 30 mA mA 5 10 mA 50 200 µA 2.2 2.4 SHDN = 5V (regulator off) SHDN = 0V (regulator on) kHz 95 VOUT = 3.3V or 5V (regulator on) SHDN Input Current 220 90 Quiescent Current Standby Quiescent Current 200 –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: The MIC4574 is not guaranteed to survive a short circuit to ground for input voltage above 24V. 4-94 April 1998• MIC4574 Micrel Block Diagrams +24V max. VIN Shutdown Enable SHDN CIN Internal Regulator Thermal Shutdown 200kHz Oscillator Current Limit Driver Comparator L1 SW VOUT 0.5A Switch D1 COUT 1.23V Bandgap Error Amp. R1 FB R2 MIC4574-x.x GND 4 Block Diagram with External Components Fixed Step-Down Regulator +24V max. VIN Shutdown Enable SHDN CIN Internal Regulator Thermal Shutdown 200kHz Oscillator VOUT Current Limit R1 Comparator Driver V REF R2 R1 + 1 R2 VOUT VREF 1 L1 SW VOUT 0.5A Switch D1 COUT Error Amp. 1.23V Bandgap R1 FB MIC4574 [Adjustable] GND Block Diagram with External Components Adjustable Step-Down Regulator April 1998• 4-95 R2 MIC4574 Micrel Functional Description 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. Output Switching The MIC4574 is a variable duty cycle switch-mode regulator with an internal power switch. Refer to the block diagrams. Supply Voltage The MIC4574 operates from a +4V to +24V unregulated input. Highest efficiency operation is from a supply voltage below +15V. 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 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. 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. Return Paths Adjustable versions require an external resistive voltage divider from the output voltage to ground, connected from the 1.23V tap to FB. 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. 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. 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. L1 3 6V to 24V 5 C1 47µF 35V SHDN MIC4574-3.3BN FB VIN SGND PGND 2 C1 C2 D1 L1 SW Nichicon Nichicon Motorola Sumida 4 For a mathematical approach to component selection and circuit design, refer to Application Note 14. 3.3V/0.5A 7 3 100µH 8V to 24V C2 220µF 16V 1 D1 1N5819 C1 47µF 35V 16V to 24V C1 33µF 63V 5 2 C1 C2 D1 L1 SW MIC4574BN VIN SGND Nichicon Nichicon Motorola Sumida Nichicon Nichicon Motorola Sumida 4 7 L1 5.0V/0.5A 100µH 1 D1 1N5819 C2 220µF 16V UPL1J470MEH, ESR = 0.34Ω UPL1C221MPH, ESR = 0.16Ω 1N5819 RCH875-101K, DCR = 0.28Ω Figure 2. 8V–24V to 5V/0.5A Buck Converter Through Hole Figure 1. 6V–24V to 3.3V/0.5A Buck Converter Through Hole SHDN SW MIC4574-5.0BN FB VIN SGND PGND 2 C1 C2 D1 L1 UPL1V470MEH, ESR = 0.34Ω UPL1C221MPH, ESR = 0.16Ω 1N5819 RCH875-101K, DCR = 0.28Ω 3 5 SHDN FB PGND 7 L1 220µH 1 MBR160 4 12V/0.5A R2 13.0k 1% R1 1.50k 1% C2 220µF 16V UPL1J330MEH, ESR = 0.35Ω UPL1C221MPH, ESR = 0.16Ω MBR160 RCH106-221K, DCR = 0.78Ω Figure 3. 16V–24V to 12V/0.5A Buck Converter Through Hole 4-96 April 1998• MIC4574 Micrel 5 6V to 24V SHDN SW MIC4574BWM VIN FB SGND PGND 10 C1 10µF 35V 4 L1 12 3 R2 2.49k 1% C3 3300pF L1 C2 330µF 6.3V R1 1.50k 1% D1 6 3.3V/0.5A 5 100µH 6V to 24V 10 C1 68µF 35V SHDN SW MIC4574-3.3BWM FB VIN SGND PGND 4 3.3V/0.5A 12 100µH C2 470µF 16V 3 D1 MBRS130LT3 6 MBRS130LT3 C1 C2 D1 L1 AVX AVX Motorola Coiltronics TPSD106M035R0300, ESR = 0.3Ω TPSE337M006R0100, ESR = 0.1Ω MBRS130LT3 CTX100-2P, DCR = 0.541Ω C1 C2 D1 L1 Figure 4. 6V–24V to 3.3V/0.5A Buck Converter Low-Profile Surface Mount 5 8V to 24V SHDN SW MIC4574BWM FB VIN SGND PGND 10 C1 10µF 35V 4 L1 12 100µH 3 35CV168GX, ESR = 0.34Ω 16CV470GX, ESR = 0.17Ω MBRS130LT3 DO3316P-104, DCR = 0.23Ω Figure 7. 6V–24V to 3.3V/0.5A Buck Converter Low-Cost Surface Mount 5V/0.5A R2 3.01k 1% L1 5 C3 3300pF C2 220µF 10V R1 1.00k 1% D1 6 Sanyo Sanyo Motorola Coilcraft 8V to 24V 10 C1 68µF 35V SHDN SW MIC4574-5.0BWM FB VIN SGND PGND 4 5V/0.5A 12 100µH 3 D1 MBRS130LT3 6 C2 470µF 16V MBRS130LT3 C1 C2 D1 L1 AVX AVX Motorola Coiltronics TPSD106M035R0300, ESR = 0.3Ω TPSE227M010R0100, ESR = 0.1Ω MBRS130LT3 CTX100-2P, DCR = 0.541Ω C1 C2 D1 L1 Figure 5. 8V–24V to 5V/0.5A Buck Converter Low-Profile Surface Mount 5 16V to 24V 10 C1 10µF 50V SHDN MIC4574BWM FB VIN SGND PGND 4 C1 C2 D1 L1 SW 6 12 L1 250µH 3 D1 SS16 C3 3300pF R1 1.50k 1% C2 68µF 20V Tokin C55Y5U1H106Z AVX TPSE686M020R0150, ESR = 0.15Ω General Instruments SS16 Coiltronics CTX250-4P, DCR = 0.434Ω 5 16V to 24V 10 C1 47µF 50V SHDN SW MIC4574BWM FB VIN SGND PGND 4 C1 C2 D1 L1 Figure 6. 16V–24V to 12V/0.5A Buck Converter Low-Profile Surface Mount April 1998• 35CV168GX, ESR = 0.34Ω 16CV470GX, ESR = 0.17Ω MBRS130LT3 DO3316P-104, DCR = 0.23Ω Figure 8. 8V–24V to 5V/0.5A Buck Converter Low-Cost Surface Mount 12V/0.5A R2 13.0k 1% Sanyo Sanyo Motorola Coilcraft 6 12 L1 220µH 3 D1 SS16 12V/0.5A R2 13.0k 1% R1 1.50k 1% C2 470µF 16V Nichicon UUX1H470MNT1GS, ESR = 0.4Ω Sanyo 16CV470GX, ESR = 0.17Ω General Instruments SS16 Coilcraft DO3316-224, DCR = 0.53Ω Figure 9. 16V–24V to 12V/0.5A Buck Converter Low-Cost Surface Mount 4-97 4