LM2575 Micrel, Inc. 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 switch-mode 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-bycycle current limiting and thermal shutdown for full protection under fault conditions. • 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 870 20 7V–40V Unregulated DC Input 1 4 +5V, 1A Regulated Output Feedback LM2575-5.0 Output L1 2 330µH 3 5 Gnd On/Off D1 1N5822 +VIN + CIN 100µF 7V–40V Unregulated DC Input +VIN + CIN 100µF + COUT 330µF Note: Pin numbers are for TO-220 Package 1 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 R2 VOUT = 1.23 1 + R1 ( Fixed Regulator in Typical Application ) Adjustable Regulator 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 April 2005 1 M9999-042205 LM2575 Micrel, Inc. Ordering Information Standard Part Number‡ Pb-Free Temperature Range Package LM2575BN* Contact Factory –40°C to +85 °C 16-pin Plastic DIP LM2575-3.3BN Contact Factory –40°C to +85 °C 16-pin Plastic DIP LM2575-5.0BN Contact Factory –40°C to +85 °C 16-pin Plastic DIP LM2575-12BN Contact Factory –40°C to +85 °C 16-pin Plastic DIP LM2575BWM* LM2575YWM* –40°C to +85°C 24-pin Wide SOIC LM2575-3.3BWM LM2575-3.3YWM –40°C to +85°C 24-pin Wide SOIC LM2575-5.0BWM LM2575-5.0YWM –40°C to +85°C 24-pin Wide SOIC LM2575-12BWM LM2575-12YWM –40°C to +85°C 24-pin Wide SOIC † LM2575BT* LM2575WT*/** –40°C to +85°C 5-lead TO-220 † LM2575-3.3WT** –40°C to +85°C 5-lead TO-220 † LM2575-5.0WT** –40°C to +85°C 5-lead TO-220 LM2575-12BT LM2575-12WT** –40°C to +85°C 5-lead TO-220 LM2575BU* LM2575WU*/** –40°C to +85°C 5-lead TO-263 LM2575-3.3BU LM2575-3.3WU** –40°C to +85°C 5-lead TO-263 LM2575-5.0BU LM2575-5.0WU** –40°C to +85°C 5-lead TO-263 LM2575-12BU LM2575-12WU** –40°C to +85°C 5-lead TO-263 LM2575-3.3BT LM2575-5.0BT † * Adjustable output regulators. **Pb-Free RoHS compliant with "hot-melting solder" exemption. † Contact factory for bent or staggered leads option. Pin Configurations 5-LEAD TO-220 (T) GND 5-LEAD TO-263 (U) GND 5- ON/OFF 4- FEEDBACK 3- GROUND 2- OUTPUT 1- VIN 5- ON/OFF 4- FEEDBACK 3- GROUND 2- OUTPUT 1- VIN 24-LEAD SOIC (WM) PWR GND NC NC NC NC NC FB SIG GND NC ON/OFF NC PWR GND 16-LEAD DIP (N) NC NC OUTPUT NC GND NC FB NC M9999-042205 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 VIN NC GND GND GND GND NC ON/OFF 2 1 2 3 4 5 6 7 8 9 10 11 12 24 23 22 21 20 19 18 17 16 15 14 13 NC NC NC NC NC NC OUTPUT OUTPUT NC VIN VIN NC April 2005 LM2575 Micrel, Inc. Absolute Maximum Ratings (Note 1) Maximum Supply Voltage ON/OFF Pin Input Voltage Output Voltage to Ground (Steady State) Power Dissipation Storage Temperature Range Minimum ESD Rating C = 100pF, R = 1.5kΩ FB Pin Lead Temperature (soldering, 10 sec.) Maximum Junction Temperature Operating Ratings 45V –0.3V ≤ V ≤ +40V –1V Internally Limited –65°C to +150°C Temperature Range Supply Voltage –40°C ≤ TJ ≤ +125°C 40V 2 kV 1 kV 260°C 150°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. LM2575 Symbol Parameter Conditions Typ Limit (Note 2) Units (Limits) 1.217 1.243 V V(min) V(max) 1.193/1.180 1.267/1.280 V V(min) V(max) SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit Figure 1 VOUT Feedback Voltage VIN = 12V , ILOAD = 0.2A VOUT = 5V 1.230 VOUT Feedback Voltage LM2575 0.2A ≤ ILOAD ≤ 1A, 8V ≤ VIN ≤ 40V VOUT = 5V 1.230 η Efficiency VIN = 12V, ILOAD = 1A, VOUT = 5V 82 % SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3) Test Circuit Figure 1 VOUT Output Voltage VIN = 12V , ILOAD = 0.2A VOUT = 3.3V 3.3 VOUT Output Voltage LM2575-3.3 0.2A ≤ ILOAD ≤ 1A, 8V ≤ VIN ≤ 40V VOUT = 3.3V 3.3 η Efficiency VIN = 12V, ILOAD = 1A 75 3.234 3.366 V V(min) V(max) 3.168/3.135 3.432/3.465 V V(min) V(max) % SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit Figure 1 VOUT Output Voltage VIN = 12V , ILOAD = 0.2A VOUT = 5V 5.0 VOUT Output Voltage LM2575-5.0 0.2A ≤ ILOAD ≤ 1A, 8V ≤ VIN ≤ 40V VOUT = 5V 5.0 η Efficiency VIN = 12V, ILOAD = 1A 82 4.900 5.100 V V(min) V(max) 4.800/4.750 5.200/5.250 V V(min) V(max) % SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit Figure 1 VOUT Output Voltage VOUT η April 2005 VIN = 25V , ILOAD = 0.2A VOUT = 12V 12 Output Voltage LM2575-12 0.2A ≤ ILOAD ≤ 1A, 15V ≤ VIN ≤ 40V VOUT = 12V 12 Efficiency VIN = 25V, ILOAD = 1A 88 3 11.760 12.240 V V(min) V(max) 11.520/11.400 12.480/12.600 V V(min) V(max) % M9999-042205 LM2575 Micrel, Inc. Electrical Characteristics (continued) Symbol Parameter Conditions LM2575 Units Typ Limit (Note 2) (Limits) 50 100/500 nA 47/42 58/63 kHz kHz (min) kHz (max) 1.2/1.4 V V(max) 93 % %(min) 1.7/1.3 3.0/3.2 A A(min) A(max) DEVICE PARAMETERS, ADJUSTABLE REGULATOR IB Feedback Bias Current VOUT = 5V DEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORS fO Oscillator Frequency VSAT Saturation Voltage DC Max Duty Cycle (ON) ICL Current Limit IL Output Leakage Current 52 IOUT = 1A (Note 4) 0.9 (Note 5) 98 Peak Current, tON ≤ 3µs (Note 4) VIN = 40V, (Note 6), (Note 6) Output = 0V Output = –1V Output = –1V IQ Quiescent Current ISTBY Standby Quiescent Current ON/OFF Pin = 5V (OFF) θJA θJA θJC θJA θJA Thermal Resistance T Package, Junction to Ambient (Note 7) T Package, Junction to Ambient (Note 8) T Package, Junction to Case N Package, Junction to Ambient (Note 9) WM Package, Junction to Amb. (Note 9) M9999-042205 (Note 6) 2.2 2 30 mA(max) mA mA(max) 10 mA mA(max) 200 µA µA(max) 7.5 5 50 4 65 45 2 85 100 °C/W April 2005 LM2575 Symbol Micrel, Inc. Parameter Conditions Typ LM2575 Units Limit (Note 2) (Limits) 2.2/2.4 1.0/0.8 V(min) V(max) 30 µA µA(max) 10 µA µA(max) 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 1.4 1.2 4 ON/OFF Pin = 0V (ON) 0.01 Note 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. Note 2: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face) . All room temperature limits are 100% production tested. All limits at temperature extreme are guaranteed via testing. Note 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. Note 4: Output (pin 2) sourcing current. No diode, inductor or capacitor connected to output. Note 5: Feedback (pin 4) removed from output and connected to 0V. Note 6: Feedback (pin 4) removed from output and connected to 12V to force the output transistor OFF. Note 7: Junction to ambient thermal resistance (no external heat sink) for the 5-lead TO-220 package mounted vertically, with 1/2" leads in a socket, or on PC board with minimum copper area. Note 8: Junction to ambient thermal resistance (no external heat sink) for the 5-lead TO-220 package mounted vertically, with 1/4" leads soldered to PC board containing approximately 4 square inches of copper area surrounding the leads. Note 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. Typical Performance Characteristics Feedback Voltage vs Duty Cycle* 20 25 20 15 10 5 VIN = 12V ILOAD = 200mA Normalized to TJ = 25˚C FEEDBACK VOLTAGE CHANGE (mV) NORMALIZED FEEDBACK VOLTAGE (mV) Normalized Feedback Voltage* 0 -5 -10 -15 -20 -25 -75 -50 -25 0 25 50 75 100 125 150 ILOAD = 200 mA 15 10 5 VIN = 40V 0 -5 VIN = 7V -10 -15 -20 0 JUNCTION TEMPERATURE (˚C) 20 40 60 80 100 DUTY CYCLE (%) * Adjustable version only April 2005 5 M9999-042205 LM2575 Micrel, Inc. Typical Performance Characteristics (continued) Supply Current vs. Duty Cycle Supply Current 17.5 SUPPLY CURRENT (mA) SUPPLY CURRENT (mA) 20.0 Measured at Ground Pin TJ = 25˚C VOUT = 5V 16 14 12 10 8 ILOAD to 1A 15.0 12.5 10.0 ILOAD = 200 mA 7.5 5.0 VIN from 7V to 40V 2.5 6 4 0 10 20 30 40 50 Standby Quiescent Current STANDBY QUIESCENT CURRENT (µA) 20 18 (Circuit of Figure 1) 0 60 0 20 INPUT VOLTAGE (V) 40 60 80 3 Efficiency 100 -55˚C -40˚C 0.8 25˚C 0.2 2.5 2.0 VOUT = 1.23V ILOAD = 200 mA 8 6 25 0 -25 -50 -75 -100 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (˚C) M9999-042205 VOUT = 3V 0 0 -2 -4 10 15 20 10 15 20 25 30 35 40 100 75 50 25 0 -25 -50 -75 -6 5 5 Feedback Pin Current 2 25 -100 -75 -50 -25 0 30 INPUT VOLTAGE (V) 25 50 75 100 125 150 JUNCTION TEMPERATURE (˚C) Oscillator Frequency +8 1A INPUT VOLTAGE (V) 4 0 Dropout Voltage 2.0 Normalized at 25˚C +6 NORMALIZED FREQUENCY (%) OUTPUT VOLTAGE CHANGE (mV) 50 1.0 Normalized to V IN = 10V VOUT = 5V ILOAD = 500mA TJ = 25 10 Normalized Output Voltage 75 0.8 Line Regulation 14 12 25 50 75 100 125 150 VIN = 12V ILOAD = 200mA Normalized to TJ = 25˚C 75 SWITCH CURRENT (A) JUNCTION TEMPERATURE (˚C) 100 0.6 STANDBY QUIESCENT CURRENT (µA) 3.0 0.4 +4 +2 0 -2 VIN = 40V -4 --6 VIN = 12V -8 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (˚C) 6 INPUT-OUTPUT DIFFERENTIAL (V) 3.5 200 mA 200 mA 80 60 0 NORMALIZED FEEDBACK VOLTAGE (mV) INPUT VOLTAGE (V) 4.0 1A 65 0.4 JUNCTION TEMPERATURE (˚C) 5.0 4.5 85 70 0.6 125˚C 150˚C Minimum Operating Voltage VOUT = 12V 90 1.0 EFFICIENCY (%) SATURATION VOLTAGE (V) OUTPUT CURRENT (A) 95 0 -75 -50 -25 0 25 50 75 100 125 150 0.5 0 -75 -50 -25 0 VIN = 12V 50 JUNCTION TEMPERATURE (˚C) VI N = 25V 1 VON/OFF = 5V 100 0 -75 -50 -25 0 25 50 75 100 125 150 100 1.2 1.0 150 Switch Saturation Voltage 2 VIN = 40V DUTY CYCLE (%) Current Limit 1.5 200 1.5 ILOAD = 1A ∆VOUT = 5% R IND = 0.2Ω 1.0 0.5 ILOAD = 200 mA 0 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (˚C) April 2005 LM2575 Micrel, Inc. Typical Performance Characteristics (Circuit of Figure 1) Load Transient Response Switching Waveforms +100mV Output Voltage Change A 10V B 1A 0 0 –100mV 0 1A C .5A 1.0A Output Current 0 0.5A 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 Test Circuits and Layout Guidelines Horizontal Time Base: 5µs/div FEEDBACK 4 +VIN LM2575 7V - 40V UNREGULATED DC INPUT + 100 µF GND 3 ON/OFF 5 VOUT 5.00V L1 OUTPUT 1 330 µH 2 + D1 MBR360 C IN R2 C OUT 470µF 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.) L O A D R1 FEEDBACK +VIN 4 LM2575-5.0 7V - 40V UNREGULATED DC INPUT + 100 µF GND 3 ON/OFF 5 VOUT 5.00V L1 OUTPUT 1 330 µH 2 + D1 MBR360 C IN C OUT 220µF 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.) L O A D Figure 1. Note: Pin numbers are for TO-220 Package As in any switching regulator, layout is very important. Rapidly switching currents associated with wiring inductance generate voltage transients which can cause problems. For minimal stray inductance and ground 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. Block Diagrams VIN 1 FEEDBACK 4 INTERNAL REGULATOR VIN INTERNAL REGULATOR 1 FEEDBACK 1 AMP SWITCH COMPARATOR + - - 4 5 ON/OFF - 2 OUTPUT RESET THERMAL SHUTDOWN CURRENT LIMIT 3 3 GND 1 AMP SWITCH COMPARATOR + DRIVER 2 52 kHz OSCILLATOR ON/OFF FIXED GAIN ERROR AMP + 1.23V BAND-GAP REFERENCE ON/OFF FIXED GAIN ERROR AMP 3.1k 1.0k 5 ON/OFF + - DRIVER OUTPUT 1.23V BAND-GAP REFERENCE GND 52 kHz OSCILLATOR RESET THERMAL SHUTDOWN CURRENT LIMIT Note: Pin numbers are for the TO-220 package Fixed Regulator April 2005 Adjustable Regulator 7 M9999-042205 LM2575 Micrel, Inc. 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) 0.130±0.005 (3.302±0.127) 0.290-0.320 (7.336-8.128) 0.020 (0.508) 0.040 TYP (1.016) 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 DIP (N) PIN 1 DIMENSIONS: INCHES (MM) 0.301 (7.645) 0.297 (7.544) 0.027 (0.686) 0.031 (0.787) 0.094 (2.388) 0.090 (2.286) 0.050 (1.270) TYP 0.016 (0.046) TYP 0.609 (15.469) 0.605 (15.367) 0.103 (2.616) 0.099 (2.515) 7° TYP 0.015 R (0.381) 0.015 (0.381) SEATING MIN PLANE 0.297 (7.544) 0.293 (7.442) 0.330 (8.382) 0.326 (8.280) 0.022 (0.559) 0.018 (0.457) 5° TYP 10° TYP 0.032 (0.813) TYP 0.408 (10.363) 0.404 (10.262) 24-Pin Wide SOP (WM) M9999-042205 8 April 2005 LM2575 Micrel, Inc. 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) 0.032 ±0.005 (0.81 ±0.13) 0.268 REF (6.81 REF) 0.018 ±0.008 (0.46 ±0.20) 0.103 ±0.013 (2.62±0.33) Dimensions: inch (mm) 5-Lead TO-220 (T) 0.405±0.005 0.176 ±0.005 0.050±0.005 0.065 ±0.010 20°±2° 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-Lead TO-263 (T) 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 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. © 1999 Micrel Incorporated April 2005 9 M9999-042205