MIC4574 Micrel MIC4574 200kHz Simple 0.5A Buck Voltage Regulator Preliminary Information 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 4:1 reduction in output filter inductor values. The MIC4574 is available in 3.3V, and 5V fixed output versions or a 1.23V to 18V 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 input voltage range: 4V to 24V • Wide output voltage range: 1.23V to 18V • Requires minimum external components • Shutdown mode < 200µA typ. • 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. The MIC4574 is available in DIP (BN) and SOIC (BWM) packages for the industrial temperature range. Applications • • • • • Simple high-efficiency step-down (buck) regulator Efficient pre-regulator for linear regulators On-card switching regulators Positive to negative converter (inverting buck-boost) Isolated flyback converter using minimum external components • Negative boost converter Typical Applications Shutdown Enable 100µH SHDN MIC4574-5.0 +8V to +24V CIN 47µF VIN PGND +5V, 0.5A SW 1N5819 COUT 220µF FB SGND Fixed Regulator Shutdown Enable 100µH SHDN MIC4574 +4.75V to +24V 1N5819 1.43k 1% FB VIN CIN 47µF +3V, 0.5A SW 1k 1% GND COUT 220µF Adjustable Regulator 4-92 1997 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 Drawings Not to Scale 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 +40V 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 1997 Pin Function 4-93 4 MIC4574 Micrel Absolute Maximum Ratings Supply Voltage (VIN) ..................................................... 45V Shutdown (SHDN) ........................................ –0.3V to +40V Output Switch (SW), Steady State ................................ –1V Operating Junction Temperature .............................. 160°C Package Thermal Resistance θJA Plastic DIP .................................................. 130°C/W θJC SOIC ........................................................... 120°C/W Storage Temperature ................................. –65°C to 150°C Electrical Characteristics TJ = 25°C. Bold indicates –40°C ≤ TJ ≤ +85°C. (Note 1) 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] Note 2 Feedback Voltage Feedback Voltage 8V ≤ VIN ≤ 24V, 0.1A ≤ ILOAD ≤ 0.5A Efficiency ILOAD = 0.5A 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 VIN = 12V, ILOAD = 100mA unless noted. Note 2 VOUT = 5V 4-94 1997 MIC4574 Micrel Block Diagrams +7V to +24V 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 +7V to +24V VIN Shutdown Enable SHDN CIN Internal Regulator Thermal Shutdown 200kHz Oscillator R1 VOUT = V REF + 1 R2 Current Limit V R1 = R2 OUT − 1 V REF Comparator Driver 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 1997 4-95 R2 MIC4574 Micrel Functional Description 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. Feedback Fixed versions of the regulator have an internal resistive divider from the feedback (FB) pin. Connect FB directly to the output line. 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. A higher feedback voltage increases the error amplifier output voltage. A higher error amplifier voltage (comparator “–” 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 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. Output Capacitor External output capacitor COUT provides stabilization and reduces ripple. 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. 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. For a mathematical approach to component selection and circuit design, refer to Application Note 14. 4-96 1997 MIC4574 Micrel 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 7 3.3V/0.5A 3 100µH D1 1N5819 4 16V to 40V C2 220µF 16V 1 C1 33µF 63V UPL1V470MEH, ESR = 0.34Ω UPL1C221MPH, ESR = 0.16Ω 1N5819 RCH875-101K, DCR = 0.28Ω 6V to 40V 5 C1 33µF 63V SHDN SW MIC4574-3.3BN FB VIN SGND PGND 2 7 L1 3.3V/0.5A C2 220µF 16V D1 MBR160 4 MIC4574BN FB VIN SGND PGND Nichicon Nichicon Motorola Sumida L1 7 12V/0.5A 220µH 1 MBR160 4 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 5. 16V–40V to 12V/0.5A Buck Converter Note 3 Through Hole 5 100µH 1 SW 2 C1 C2 D1 L1 Figure 1. 6V–24V to 3.3V/0.5A Buck Converter Through Hole 3 5 SHDN 6V to 18V 10 C1 10µF 35V SHDN SW MIC4574BWM FB VIN SGND PGND 4 L1 12 100µH 3 C3 3300pF C2 330µF 6.3V R1 1.50k 1% D1 6 3.3V/0.5A R2 2.49k 1% MBRS130LT3 C1 C2 D1 L1 Nichicon Nichicon Motorola Sumida UPL1J330MEH, ESR = 0.35Ω UPL1C221MPH, ESR = 0.16Ω MBR160 RCH875-101K, DCR = 0.28Ω C1 C2 D1 L1 Figure 2. 6V–40V to 3.3V/0.5A Buck Converter Note 3 Through Hole 3 8V to 24V 5 C1 47µF 35V SHDN MIC4574-5.0BN FB VIN SGND PGND 2 C1 C2 D1 L1 SW Nichicon Nichicon Motorola Sumida 7 L1 5.0V/0.5A 5 100µH D1 1N5819 4 6V to 36V C2 220µF 16V 1 8V to 40V 5 C1 33µF 63V SHDN MIC4574-5.0BN FB VIN SGND PGND 2 4 7 L1 10 C1 10µF 50V C1 C2 D1 L1 D1 MBR160 SW MIC4574BWM FB VIN SGND PGND L1 12 100µH 3 D1 SS16 6 3.3V/0.5A R2 2.49k 1% C3 3300pF C2 330µF 6.3V R1 1.50k 1% Figure 7. 6V–36V to 3.3V/0.5A Buck Converter Note 3 Low-Profile Surface Mount 5V/0.5A C2 220µF 16V 4 Tokin C55Y5U1H106Z AVX TPSE337M006R0100, ESR = 0.1Ω General Instruments SS16 Coiltronics CTX100-2P, DCR = 0.541Ω 5 100µH 1 SHDN 4 UPL1J470MEH, ESR = 0.34Ω UPL1C221MPH, ESR = 0.16Ω 1N5819 RCH875-101K, DCR = 0.28Ω SW TPSD106M035R0300, ESR = 0.3Ω TPSE337M006R0100, ESR = 0.1Ω MBRS130LT3 CTX100-2P, DCR = 0.541Ω Figure 6. 6V–18V to 3.3V/0.5A Buck Converter Low-Profile Surface Mount Figure 3. 8V–24V to 5V/0.5A Buck Converter Through Hole 3 AVX AVX Motorola Coiltronics 8V to 18V 10 C1 10µF 35V SHDN SW MIC4574BWM FB VIN SGND PGND 4 6 L1 12 100µH 3 D1 5V/0.5A R2 3.01k 1% C3 3300pF R1 1.00k 1% C2 220µF 10V MBRS130LT3 C1 C2 D1 L1 Nichicon Nichicon Motorola Sumida UPL1J330MEH, ESR = 0.35Ω UPL1C221MPH, ESR = 0.16Ω MBR160 RCH875-101K, DCR = 0.28Ω C1 C2 D1 L1 Figure 4. 8V–40V to 5V/0.5A Buck Converter Note 3 Through Hole Note 3 1997 AVX AVX Motorola Coiltronics TPSD106M035R0300, ESR = 0.3Ω TPSE227M010R0100, ESR = 0.1Ω MBRS130LT3 CTX100-2P, DCR = 0.541Ω Figure 8. 8V–18V to 5V/0.5A Buck Converter Low-Profile Surface Mount Although the MIC457x family is functional to input voltage to 40V they are not guaranteed to survive a short circuit to ground for input voltage above 24V. Contact Micrel for availablity of 40V parts. 4-97 MIC4574 Micrel 5 8V to 36V SHDN SW MIC4574BWM FB VIN SGND PGND 10 C1 10µF 50V 4 C1 C2 D1 L1 L1 12 R2 3.01k 1% 100µH 3 C3 3300pF 5 C2 220µF 10V R1 1.00k 1% D1 SS16 6 L1 5V/0.5A 5 SHDN SW MIC4574BWM FB VIN SGND PGND 10 C1 10µF 50V 4 C1 C2 D1 L1 3 D1 SS16 6 R2 13.0k 1% C3 3300pF R1 1.50k 1% C2 68µF 20V 8V to 36V L1 6V to 24V 10 C1 68µF 35V MIC4574-3.3BWM FB VIN SGND PGND 4 C1 C2 D1 L1 SW Sanyo Sanyo Motorola Coilcraft 12 C1 47µF 50V D1 MBRS130LT3 5 16V to 36V C2 470µF 16V 6V to 36V 10 C1 47µF 50V MIC4574-3.3BWM FB VIN SGND PGND 4 C1 C2 D1 L1 SW 6 12 SHDN SW MIC4574-5.0BWM FB VIN SGND PGND 6 5V/0.5A 12 100µH C2 470µF 16V 3 D1 SS16 Nichicon UUX1H470MNT1GS, ESR = 0.4Ω Sanyo 16CV470GX, ESR = 0.17Ω General Instruments SS16 Coilcraft DO3316P-104, DCR = 0.23Ω SHDN SW MIC4574BWM FB VIN SGND PGND 4 C1 C2 D1 L1 35CV168GX, ESR = 0.34Ω 16CV470GX, ESR = 0.17Ω MBRS130LT3 DO3316P-104, DCR = 0.23Ω L1 SHDN 10 C1 47µF 50V 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 15. 16V–36V to 12V/0.5A Buck Converter Note 3 Lower-Cost Surface Mount Figure 11. 6V–24V to 3.3V/0.5A Buck Converter Lower-Cost Surface Mount 5 35CV168GX, ESR = 0.34Ω 16CV470GX, ESR = 0.17Ω MBRS130LT3 DO3316P-104, DCR = 0.23Ω Figure 14. 8V–36V to 5V/0.5A Buck Converter Note 3 Lower-Cost Surface Mount 3.3V/0.5A 3 6 4 100µH 6 10 C1 C2 D1 L1 Figure 10. 16V–36V to 12V/0.5A Buck Converter Note 3 Low-Profile Surface Mount SHDN D1 MBRS130LT3 L1 5 Tokin C55Y5U1H106Z AVX TPSE686M020R0150, ESR = 0.15Ω General Instruments SS16 Coiltronics CTX250-4P, DCR = 0.434Ω 5 C2 470µF 16V 3 Figure 13. 8V–24V to 5V/0.5A Buck Converter Lower-Cost Surface Mount 12V/0.5A 250µH 100µH MIC4574-5.0BWM FB VIN SGND PGND Sanyo Sanyo Motorola Coilcraft 5V/0.5A 12 SW 4 C1 C2 D1 L1 L1 12 10 C1 68µF 35V Tokin C55Y5U1H106Z AVX TPSE227M010R0100, ESR = 0.1Ω General Instruments SS16 Coiltronics CTX100-2P, DCR = 0.541Ω Figure 9. 8V–36V to 5V/0.5A Buck Converter Note 3 Low-Profile Surface Mount 16V to 36V 8V to 24V SHDN 3.3V/0.5A 100µH 3 D1 SS16 C2 470µF 16V Nichicon UUX1H470MNT1GS, ESR = 0.4Ω Sanyo 16CV470GX, ESR = 0.17Ω General Instruments SS16 Coilcraft DO3316P-104, DCR = 0.23Ω Figure 12. 6V–36V to 3.3V/0.5A Buck Converter Note 3 Lower-Cost Surface Mount Note 3 Although the MIC457x family is functional to input voltage to 40V they are not guaranteed to survive a short circuit to ground for input voltage above 24V. Contact Micrel for availablity of 40V parts. 4-98 1997