LM2576 Micrel, Inc. LM2576 52kHz Simple 3A Buck Regulator General Description Features The LM2576 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, or 12V fixed output. Adjustable versions have an output voltage range from 1.23V to 37V. Both versions are capable of driving a 3A 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 LM2576 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 LM2576 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 3A 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 Note: Pin numbers are for TO-220 Package 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 VOUT = 1.23 1 + R2 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 August 2005 1 M9999-082605-B LM2576 Micrel, Inc. Ordering Information Part Number‡ Standard RoHS Compliant** LM2576BT*† LM2576WT*† † LM2576-3.3BT † Range Temperature Package –40°C to +85°C TO-220-5 † –40°C to +85°C TO-220-5 † LM2576-3.3WT LM2576-5.0BT LM2576-5.0WT –40°C to +85°C TO-220-5 † † LM2576-12BT LM2576-12WT –40°C to +85°C TO-220-5 LM2576BU* LM2576WU* –40°C to +85°C TO-263-5 LM2576-3.3BU LM2576-3.3WU –40°C to +85°C TO-263-5 LM2576-5.0BU LM2576-5.0WU –40°C to +85°C TO-263-5 LM2576-12BU LM2576-12WU –40°C to +85°C TO-263-5 * Adjustable output regulators. **RoHS compliant with "hot-melting solder" exemption. † Contact factory for bent or staggered leads option. Pin Configurations 5-LEAD TO-220 (T) GND M9999-082605-B 5-LEAD TO-263 (U) GND 5- ON/OFF 4- FEEDBACK 3- GROUND 2- OUTPUT 1- VIN 2 5- ON/OFF 4- FEEDBACK 3- GROUND 2- OUTPUT 1- VIN August 2005 LM2576 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 –40°C ≤ TJ ≤ +125°C 40V Temperature Range Supply Voltage 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 = 500mA. LM2576 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 = 0.5A VOUT = 5V 1.230 VOUT Feedback Voltage LM2576 0.5A ≤ ILOAD ≤ 3A, 8V ≤ VIN ≤ 40V VOUT = 5V 1.230 η Efficiency VIN = 12V, ILOAD = 3A, VOUT = 5V 82 % SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3) Test Circuit Figure 1 VOUT Output Voltage VIN = 12V , ILOAD = 0.5A VOUT = 3.3V 3.3 VOUT Output Voltage LM2576-3.3 0.5A ≤ ILOAD ≤ 3A, 6V ≤ VIN ≤ 40V VOUT = 3.3V 3.3 η Efficiency VIN = 12V, ILOAD = 3A 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 = 0.5A VOUT = 5V 5.0 VOUT Output Voltage LM2576-5.0 0.5A ≤ ILOAD ≤ 3A, 8V ≤ VIN ≤ 40V VOUT = 5V 5.0 η Efficiency VIN = 12V, ILOAD = 3A 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 VIN = 25V , ILOAD = 0.5A VOUT = 12V 12 VOUT Output Voltage LMLM2576-12 0.5A ≤ ILOAD ≤ 3A, 15V ≤ VIN ≤ 40V VOUT = 12V 12 η Efficiency VIN = 25V, ILOAD = 3A 88 August 2005 3 11.760 12.240 V V(min) V(max) 11.520/11.400 12.480/12.600 V V(min) V(max) % M9999-082605-B LM2576 Micrel, Inc. Electrical Characteristics (continued) Symbol Parameter Conditions LM2576 Units Typ Limit (Note 2) (Limits) 50 100/500 nA 47/42 58/63 kHz kHz (min) kHz (max) 1.8/2.0 V V(max) 93 % %(min) 4.2/3.5 6.9/7.5 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 = 3A (Note 4) 1.4 (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 Thermal Resistance T,U Package, Junction to Ambient (Note 7) T,U Package, Junction to Ambient (Note 8) T,U Package, Junction to Case M9999-082605-B (Note 6) 5.8 2 30 mA(max) mA mA(max) 10 mA mA(max) 200 µA µA(max) 7.5 5 50 4 65 45 2 °C/W August 2005 LM2576 Micrel, Inc. Electrical Characteristics (continued) Symbol Parameter Conditions Typ LM2576 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 LM2576/LM1576 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 ILOAD = 200 mA 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 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 August 2005 5 M9999-082605-B LM2576 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 ILOAD to 1A 8 15.0 12.5 10.0 ILOAD = 200 mA 7.5 5.0 6 4 VIN from 7V to 40V 2.5 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 1.0 -55˚C -40˚C 0.8 25˚C 0.6 125˚C 150˚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) M9999-082605-B VOUT = 3V 0 0 10 15 20 10 15 20 25 30 75 50 25 0 -25 -50 -75 25 -100 -75 -50 -25 0 30 INPUT VOLTAGE (V) 25 50 75 100 125 150 JUNCTION TEMPERATURE (˚C) Oscillator Frequency Dropout Voltage 2.0 Normalized at 25˚C +6 +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 35 40 100 -6 5 5 Feedback Pin Current -2 -4 +8 1A INPUT VOLTAGE (V) 2 0 NORMALIZED FREQUENCY (%) OUTPUT VOLTAGE CHANGE (mV) 50 1.0 4 25 50 75 100 125 150 VIN = 12V ILOAD = 200mA Normalized to TJ = 25˚C 0.8 Normalized to V IN = 10V VOUT = 5V ILOAD = 500mA TJ = 25 10 Normalized Output Voltage 75 0.6 Line Regulation 14 12 JUNCTION TEMPERATURE (˚C) 100 0.4 STANDBY QUIESCENT CURRENT (µA) 3.0 75 65 INPUT-OUTPUT DIFFERENTIAL (V) 3.5 200 mA 200 mA 80 SWITCH CURRENT (A) NORMALIZED FEEDBACK VOLTAGE (mV) INPUT VOLTAGE (V) 4.0 1A 60 0 JUNCTION TEMPERATURE (˚C) 5.0 4.5 85 70 0.4 Minimum Operating Voltage VOUT = 12V 90 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) August 2005 LM2576 Micrel, Inc. Typical Performance Characteristics (Circuit of Figure 1) Load Transient Response +100mV Output Voltage Change 0 -100mV 3A Output Current 2A 1A 0 100 µS/div. Switching Waveforms 50V A 0 4A B 2A 0 4A C 2A 0 D 5 µS/div. V OUT = 5V VIN = 45V A: Output pin voltage 50V/div B: Output pin current 2A/div C: Inductor current 2A/div D: Output ripple voltage 50 mV/div., AC coupled Horizontal Time Base: 5µS/div August 2005 7 M9999-082605-B LM2576 Micrel, Inc. Test Circuits and Layout Guidelines FEEDBACK +VIN 4 LM2575 7V - 40V UNREGULATED DC INPUT + 100 µF GND 3 330 µH 2 ON/OFF 5 VOUT 5.00V L1 OUTPUT 1 + D1 MBR360 CIN R2 COUT 470µF R1 CIN — 100µF, 75V Aluminum Electrolytic COUT — 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 FEEDBACK +VIN 4 LM2575-5.0 7V - 40V UNREGULATED DC INPUT + 100 µF GND 3 330 µH 2 ON/OFF 5 VOUT 5.00V L1 OUTPUT 1 + D1 11DQ06 CIN COUT 220µF CIN — 100µF, 75V Aluminum Electrolytic COUT — 330µF, 15V Aluminum Electrolytic D1 — Schottky, 11DQ06 L1 — 100µH, 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 Note: 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 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 V IN 1 FEEDBACK 4 INTERNAL REGULATOR V IN INTERNAL REGULATOR 1 + - FEEDBACK 3 AMP SWITCH COMPARATOR - 4 5 ON/OFF - 2 OUTPUT RESET THERMAL SHUTDOWN CURRENT LIMIT 3 3 GND 3 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 M9999-082605-B Adjustable Regulator 8 August 2005 LM2576 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) 0.032 ±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) 0.176 ±0.005 0.405±0.005 0.065 ±0.010 20°±2° 0.060 ±0.005 0.050±0.005 0.360±0.005 0.600±0.025 SEATING PLANE 0.004 +0.004 –0.008 8° MAX 0.032 ±0.003 0.067±0.005 0.100 ±0.01 0.015 ±0.002 DIM. = INCH 5-Lead TO-263 (U) MICREL INC. 2180 FORTUNE DRIVE TEL + 1 (408) 944-0800 FAX SAN JOSE, CA 95131 + 1 (408) 474-1000 WEB USA 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. © 2005 Micrel, Incorporated. August 2005 9 M9999-082605-B