LM2575 52kHz Simple 1A Buck Regulator General Description Features The LM2575 series of monolithic integrated circuits provide all the active functions for a step-down (buck) switching regulator. Fixed versions are available with a 3.3V, 5V, 12V, fixed output. Adjustable versions have an output voltage range from 1.23V to 37V. Both versions are capable of driving a 1A load with excellent line and load regulation. These regulators are simple to use because they require a minimum number of external components and include internal frequency compensation and a fixed-frequency oscillator. The LM2575 series offers a high efficiency replacement for popular three-terminal adjustable linear regulators. It substantially reduces the size of the heat sink, and in many cases no heat sink is required. A standard series of inductors available from several different manufacturers are ideal for use with the LM2575 series. This feature greatly simplifies the design of switchmode power supplies. The feedback voltage is guaranteed to ±2% tolerance for adjustable versions, and the output voltage is guaranteed to ±3% for fixed versions, within specified input voltages and output load conditions. The oscillator frequency is guaranteed to ±10%. External shutdown is included, featuring less than 200µA standby current. The output switch includes cycle-by-cycle current limiting and thermal shutdown for full protection under fault conditions. Data sheets and support documentation can be found on Micrel’s web site at www.micrel.com. • 3.3V, 5V, 12V, 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 output current • Wide input voltage range – 4V to 40V • Wide output voltage range – 1.23V to 37V • Requires only 4 external components • 52kHz fixed frequency internal oscillator • Low power standby mode IQ typically <200µA • 80% efficiency (adjustable version typically >80%) • Uses readily available standard inductors • Thermal shutdown and current limit protection • 100% electrical thermal limit burn-in 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 number of external components • Negative boost converter ___________________________________________________________________________________________________________ Typical Applications 7V–40V Unregulated DC Input 1 4 LM2575-5.0 Output L1 2 330µH 3 5 Gnd On/Off D1 1N5822 +VIN + CIN 100µF 7V–40V Unregulated DC Input +5V, 1A Regulated Output Feedback 1 +VIN + CIN 100µF + COUT 330µF 4 LM2575 3 5 Gnd On/Off +5V, 1A Regulated Output Feedback Output L1 2 330µH D1 1N5822 + R2 3.09k COUT 330µF R1 1k Note: Pin numbers are for TO-220 Package Note: Pin numbers are for TO-220 Package ( VOUT = 1.23 1 + R2 R1 Fixed Regulation in Typical Application ) Adjustable Regulation in Fixed Output Application Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com May 2009 1 M9999-051209-B Micrel, Inc. LM2575 Ordering Information Part Number Pb-Free / RoHS Compliant Standard Temperature Range Package LM2575BN* Contact Factory –40° to +85°C 16-Pin Plastic DIP LM2575-3.3BN Contact Factory –40° to +85°C 16-Pin Plastic DIP LM2575-5.0BN LM2575-5.0YN –40° to +85°C 16-Pin Plastic DIP LM2575-12BN LM2575-12YN –40° to +85°C 16-Pin Plastic DIP LM2575BWM* LM2575YWM* –40° to +85°C 24-Pin Wide SOIC LM2575-3.3BWM LM2575-3.3YWM –40° to +85°C 24-Pin Wide SOIC LM2575-5.0BWM LM2575-5.0YWM –40° to +85°C 24-Pin Wide SOIC LM2575-12BWM LM2575-12YWM –40° to +85°C 24-Pin Wide SOIC LM2575BT*† LM2575WT*/** –40° to +85°C 5-Pin TO-220 LM2575-3.3BT † LM2575-3.3WT** –40° to +85°C 5-Pin TO-220 LM2575-5.0BT † LM2575-5.0WT** –40° to +85°C 5-Pin TO-220 LM2575-12BT† LM2575-12WT** –40° to +85°C 5-Pin TO-220 LM2575BU* LM2575WU*/** –40° to +85°C 5-Pin TO-263 LM2575-3.3BU LM2575-3.3WU** –40° to +85°C 5-Pin TO-263 LM2575-5.0BU LM2575-5.0WU** –40° to +85°C 5-Pin TO-263 LM2575-12BU LM2575-12WU** –40° to +85°C 5-Pin TO-263 Notes: * Adjustable output regulators. ** RoHS compliant with "high-melting solder" exemption. † Contact factory for bent or staggered leads option. May 2009 2 M9999-051209-B Micrel, Inc. LM2575 Pin Configuration 5-Pin TO-220 (T) ON/OFF FB GND OUT VIN 5-Pin TO-263 (U) PWR GND 1 24 NC NC 2 23 NC NC 3 22 NC NC 4 21 NC NC 1 16 VIN NC 5 20 NC NC 2 15 NC NC 6 19 NC OUT 3 14 GND FB 7 18 OUT NC 4 13 GND SIG GND 8 17 OUT GND 5 12 GND NC 9 16 NC NC 6 11 GND ON/OFF 10 15 VIN FB 7 10 NC NC 11 14 VIN NC 8 9 ON/OFF PWR GND 12 13 NC 16-Pin Plastic DIP (N) May 2009 5 4 3 2 1 TAB TAB 5 ON/OFF 4 FB 3 GND 2 OUT 1 VIN 24-Pin Wide SOIC (WM) 3 M9999-051209-B Micrel, Inc. LM2575 Absolute Maximum Ratings(1) Operating Ratings Maximum Supply Voltage (VIN) ......................................45V ON/OFF Pin Input Voltage. ......................–0.3V ≤ V ≤ +40V Output Voltage to Ground (Steady State) ......................–1V Power Dissipation .....................................Internally Limited Maximum Junction Temperature................................ 150°C Lead Temperature (soldering, 10 sec.)...................... 260°C Storage Temperature (Ts) .........................–65°C to +150°C Minimum ESD Rating C = 100pF, R = 1.5kΩ.............................................. 2kV FB Pin ...................................................................... 1kV Supply Voltage (VIN).......................................................40V Junction Temperature Range (TJ).......–40°C ≤ TJ ≤ +125°C Electrical Characteristics Specifications with standard typeface are for TJ = 25°C, and those with boldface type apply over full Operating Temperature Range. Unless otherwise specified, VIN = 12V, and ILOAD = 200mA. Symbol Parameter Condition SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit Figure 1 Feedback Voltage VOUT Feedback Voltage LM2575 VIN = 12V , ILOAD = 0.2A VOUT = 5V 1.230 0.2A ≤ ILOAD ≤ 1A, 8V ≤ VIN ≤ 40V VOUT = 5V 1.230 η Efficiency VIN = 12V, ILOAD = 1A, VOUT = 5V SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3) Test Circuit Figure 1 Output Voltage VOUT Output Voltage LM2575-3.3 VOUT Output Voltage LM2575-5.0 VOUT η May 2009 Output Voltage LM2575-12 Efficiency 1.193/1.180 1.267/1.280 82 3.3 0.2A ≤ ILOAD ≤ 1A, 8V ≤ VIN ≤ 40V VOUT = 3.3V 3.3 3.234 3.366 3.168/3.135 3.432/3.465 75 VIN = 12V , ILOAD = 0.2A VOUT = 5V 5.0 0.2A ≤ ILOAD ≤ 1A, 8V ≤ VIN ≤ 40V VOUT = 5V 5.0 η Efficiency VIN = 12V, ILOAD = 1A SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit Figure 1 Output Voltage 1.217 1.243 VIN = 12V , ILOAD = 0.2A VOUT = 3.3V η Efficiency VIN = 12V, ILOAD = 1A SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit Figure 1 Output Voltage Typ 4.900 5.100 4.800/4.750 5.200/5.250 82 VIN = 25V , ILOAD = 0.2A VOUT = 12V 12 0.2A ≤ ILOAD ≤ 1A, 15V ≤ VIN ≤ 40V VOUT = 12V 12 VIN = 25V, ILOAD = 1A 88 4 LM2575 Limit (Note 2) 11.760 12.240 11.520/11.400 12.480/12.600 Units (Limits) V V(min) V(max) V V(min) V(max) % V V(min) V(max) V V(min) V(max) % V V(min) V(max) V V(min) V(max) % V V(min) V(max) V V(min) V(max) % M9999-051209-B Micrel, Inc. LM2575 Typ LM2575 Limit (Note 2) Units (Limits) IB Feedback Bias Current VOUT = 5V DEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORS 50 100/500 nA fO Oscillator Frequency 52 VSAT Saturation Voltage IOUT = 1A (Note 4) 0.9 DC Max Duty Cycle (ON) (Note 5) 98 ICL Current Limit Peak Current, tON ≤ 3µs (Note 4) 2.2 IL Output Leakage Current VIN = 40V, (Note 6), IQ Quiescent Current (Note 6) (Note 6) ISTBY Standby Quiescent Current ON/OFF Pin = 5V (OFF) Symbol Parameter Condition DEVICE PARAMETERS, ADJUSTABLE REGULATOR 47/42 58/63 1.2/1.4 93 Output = 0V Output = –1V Output = –1V 75 30 5 10 50 200 T Package, Junction to Ambient (Note 7) θJA Thermal Resistance T Package, Junction to Ambient (Note 8) θJA θJC T Package, Junction to Case N Package, Junction to Ambient (Note 9) θJA WM Package, Junction to Ambient (Note 9) θJA ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS Test Circuit Figure 1 VIH VIL ON/OFF Pin Logic Input Level VOUT = 0V VOUT = 5V IIH ON/OFF Pin Logic Current ON /OFF Pin = 5V (OFF) IIL 1.7/1.3 3.0/3.2 2 65 45 2 85 100 1.4 1.2 2.2/2.4 1.0/0.8 4 30 ON /OFF Pin = 0V (ON) 0.01 10 kHz kHz(min) kHz(max) V V(max) % %(max) A A(min) A(max) mA(max) mA mA(max) mA mA(max) µA µA(max) °C/W V(min) V(max) µA µA(max) µA µA(max) Notes: 1. Absolute Maximum Rating indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. 2. All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are100% production tested. All limits at temperature extreme are guaranteed via testing. 3. External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. When the LM2575/LM1575 is used as shown in Figure 1 test circuit, system performance will be shown in system parameters section of Electrical Characteristics. 4. Output (pin 2) sourcing current. No diode, inductor or capacitor connected to output. 5. Feedback (pin 4) removed from output and connected to 0V. 6. Feedback (pin 4) removed from output and connected to 12V to force the output transistor OFF. 7. Junction to ambient thermal resistance (no external heat sink) for the 5-pin TO-220 package mounted vertically, with 1/2" leads in a socket, or on PC board with minimum copper area. 8. Junction to ambient thermal resistance (no external heat sink) for the 5-pin TO-220 package mounted vertically, with 1/4" leads soldered to PC board containing approximately 4 square inches of copper area surrounding the leads. 9. Junction to ambient thermal resistance with approximately 1 square inch of pc board copper surrounding the leads. Additional copper will lower thermal resistance further. May 2009 5 M9999-051209-B Micrel, Inc. LM2575 Test Circuits and Layout Guidelines FEEDBACK +VIN LM2575 1 7V - 40V U N R E G U L A TE D + DC INPUT 100µF 4 G ND 3 ON/OFF OU TPU T 5 VOUT 5.00V L1 330µH 2 + D1 MBR360 C IN R2 C OUT 470µF R1 L O A D C IN — 100µF, 75V Aluminum Electrolytic C OUT — 470µF, 15V Aluminum Electrolytic D1 — Schottky, MBR360 L1 — 330µH, 415-0926 (AIE) R1 — 1k, 0.01% R2 — 3.065k, 0.01% 5-pin TO-220 socket—2936 (Loranger Mfg. Co.) 4-pin TO-3 socket—8112-AG7 (Augat Inc.) FEEDBACK +VIN 1 7V - 40V U N R E G U L A TE D + DC INPUT 100µF LM2575-5.0 G ND 3 ON/OFF C IN 5 4 OU TPU T 2 VOUT 5.00V L1 330µH + D1 MBR360 C OUT 220µF L O A D C IN — 100µF, 75V Aluminum Electrolytic C OUT — 330µF, 15V Aluminum Electrolytic D1 — Schottky, MBR360 L1 — 330µH, 415-0926 (AIE) 5-pin TO-220 socket — 2936 (Loranger Mfg. Co.) 4-pin TO-3 socket — 8112-AG7 (Augat Inc.) Not e: Pin numbers are for TO-220 Package Figure 1. As in any switching regulator, layout is very important. Rapidly switching currents associated with wiring inductance generate voltage transient switch can cause problems. For minimal stray inductance and ground May 2009 loops, the length of the leads indicated by heavy lines should be kept as short as possible. Single-point grounding (as indicated) or ground plane construction should be used for best results. 6 M9999-051209-B Micrel, Inc. LM2575 Supply Current vs. Duty Cycle 20 20.0 Measured at Ground Pin TJ VOUT = 5V 18 16 S U P P LY C U R R E N T ( m A ) SUP PLY CURRE NT (mA ) Supply Current 14 12 10 I LO AD to 1A 8 17.5 15.0 12.5 10.0 5.0 6 2.0 4 0 0 10 20 30 40 50 60 I L O AD= 200 mA 7.5 VIN from 7V to 40V 0 20 INPUT VOLTAGE ( V) 1 100 0 -75 -50 -25 0 25 50 75 100125 150 150 VIN= 12V 50 0 -75 -50 -25 0 25 50 75 100 125150 100 95 1.0 -55 C -40 C 0.8 25 C 0.6 125 C 150 C 0.4 0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -75 -50 -25 0 VO U T = 1.23V IL OAD= 200 mA 85 25 50 75 100125150 0.2 0.4 0.6 0.8 75 1A VOUT = 3V 0 -2 -4 10 15 20 25 0 5 10 15 20 25 30 35 40 INPUT VOLTAGE ( V) 2 5 200 mA 200 mA 80 60 1.0 Line Regulation 0 1A 65 14 12 Normalized toVIN = 10V VOUT = 5V 10 I = 500mA 8 LO AD TJ = 25 6 4 -6 VOUT = 12V 90 70 30 S TA N D B Y Q U I E S C E N T C U R R E N T ( µ A ) 4.0 N O R M ALI ZED FEED BAC K VO LTAG E ( m V) INPUT VOLTAGE ( V) 5.0 4.5 VON/OFF= 5V 100 SW I TC H C U R R EN T ( A) Minimum Operating Voltage VIN = 40V Efficiency 1.2 EFFI CI ENCY ( % ) 2 80 200 Switch Saturation Voltage SATU R ATI O N VO LTAG E ( V) O U TPU T C U R R EN T ( A) VIN = 25V 60 Standby Quiescent Current D U TY C YC L E ( % ) Current Limit 3 40 S TA N D B Y Q U I E S C E N T C U R R E N T ( µ A ) Typical Characteristics (circuit of Figure 1) Feedback Pin Current 100 75 50 25 0 -25 -50 -75 -100 -75 -50 -25 0 25 50 75 100 125150 May 2009 Normalized Output Voltage 75 50 VIN = 12V I LO AD = 200mA Normalized toTJ = 25 C 25 0 -25 -50 -75 -100 -75 -50 -25 0 25 50 75 100125150 Oscillator Frequency +8 +6 Normalized at 25C +4 +2 0 -2 VIN = 40V -4 --6 VIN = 12V -8 -75 -50 -25 0 25 50 75 100125150 7 Dropout Voltage INPUT- OUTPUT DIFFERENTIAL ( V) 100 NO RM ALI ZED FREQ UENCY ( % ) O UTPUT VO LTAG E CHANG E ( m V) INPUT VOL TAGE ( V) 2.0 1.5 I LO AD= 1A VOUT = 5% RIND = 0.2 1.0 0.5 I LO AD = 200 mA 0 -75 -50 -25 0 25 50 75 100125150 M9999-051209-B Micrel, Inc. LM2575 Normalized Feedback Voltage* 25 20 15 10 5 FE E D B A C K V O LTA G E C H A N G E ( m V ) N O R M ALI ZED FEED BAC K VO LTAG E ( m V) Typical Characteristics (continued) VIN = 12V IL O AD= 200mA Normalized toTJ = 25 C 0 -5 -10 -15 -20 -25 -75 -50 -25 0 25 50 75 100125150 Feedback Voltage vs Duty Cycle* 20 I LO AD = 200 mA 15 10 5 VIN = 40V 0 -5 VIN = 7V -10 -15 -20 0 20 40 60 80 100 D U TY C YC LE ( % ) * Adjustable version only May 2009 8 M9999-051209-B Micrel, Inc. LM2575 Functional Characteristics (circuit of Figure 1) Load Transient Response Output Voltage Change Switching Waveforms +100mV A 10V 0 0 –100mV B 1A 0 1A C 1.0A Output Current .5A 0.5A 0 D 0 100µs/div. V OUT = 5V VIN = 20V V OUT = 5V A: Output pin voltage 10V/div B: Output pin current 1A/div C: Inductor current 0.5A/div D: Output ripple voltage 20 mV/div. AC coupled Horizontal Time Base: 5µs/div Functional Diagrams V IN 1 FB 4 INTERNAL REGULATOR 5 ON/OFF 2 OUT 3 GND 5 ON/OFF 2 OUT 3 GND FIXED GAIN ERROR AMP 3.1k + - - 1.23V BAND-GAP REFERENCE 1 AMP SWITCH COMPARATOR + 1.0k ON/OFF 52 kHz OSCILLATOR DRIVER RESET THERMAL SHUTDOWN CURRENT LIMIT Note: Pin numbers are for the TO-220 package Fixed Regulator VIN INTERNAL REGULATOR 1 ON/OFF FIXED GAIN ERROR AMP FB 4 - 1.23V BAND-GAP REFERENCE 1 AMP SWITCH COMPARATOR + + - 52 kHz OSCILLATOR DRIVER RESET THERMAL SHUTDOWN CURRENT LIMIT Adjustable Regulator May 2009 9 M9999-051209-B Micrel, Inc. LM2575 Package Information 0.780 MAX (19.812) PIN 1 0.030-0.110 RAD (0.762-2.794) .250±0.005 (6.350±0.127) 0.025±0.015 (0.635±0.381) 0.290-0.320 (7.336-8.128) 0.020 (0.508) 0.040 TYP (1.016) 0.130±0.005 (3.302±0.127) 0-10 0.020 MIN (0.508) 0.009-0.015 (0.229-0.381) 0.018±0.003 (0.457±0.076) 0.100±0.010 (2.540±0.254) 0.125 MIN (3.175) +0.025 –0.015 +0.635 8.255 –0.381 0.325 ( ) 16-Pin Plastic DIP (N) 24-Pin Wide SOIC (WM) May 2009 10 M9999-051209-B Micrel, Inc. LM2575 5-Pin TO-220 (T) 5-Pin TO-263 (T) May 2009 11 M9999-051209-B Micrel, Inc. LM2575 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 The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can 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 Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2000 Micrel, Incorporated. May 2009 12 M9999-051209-B