LM2576-3.3BT

LM2576 Micrel LM2576 52kHz Simple 3A Buck Voltage Regulator General Description 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. Features • 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 870 20 7V–40V Unregulated DC Input +VIN + CIN 100µF LM2576-5.0 Output L1 2 100µH 3 5 Gnd On/Off D1 1N5822 1 4 Feedback +5V, 3A Regulated Output + COUT 1000µF 7V–40V Unregulated DC Input 1 4 LM2576 Feedback +VIN + CIN 100µF 3 5 Gnd On/Off Output L1 2 100µH D1 1N5822 +5V, 3A Regulated Output + COUT 1000µF R2 3.09k 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 Regulator in Typical Application Adjustable Regulator in Fixed Output Application 4-120 October 1998 LM2576 Micrel Ordering Information Part Number‡ LM2576BT* † † † Temperature Range –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C Package 5-lead TO-220 5-lead TO-220 5-lead TO-220 5-lead TO-220 5-lead TO-263 5-lead TO-263 5-lead TO-263 5-lead TO-263 LM2576-3.3BT LM2576-5.0BT LM2576-12BT LM2576BU* † LM2576-3.3BU LM2576-5.0BU LM2576-12BU * Adjustable output regulators. † Contact factory for bent or staggered leads option. 4 Pin Configurations 5-LEAD TO-220 (T) GND 5- ON/OFF 4- FEEDBACK 3- GROUND 2- OUTPUT 1- VIN GND 5-LEAD TO-263 (U) 5- ON/OFF 4- FEEDBACK 3- GROUND 2- OUTPUT 1- VIN October 1998 4-121 LM2576 Micrel 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 45V –0.3V ≤ V ≤ +40V –1V Internally Limited –65°C to +150°C 2 kV 1 kV 260°C 150°C Operating Ratings Temperature Range Supply Voltage –40°C ≤ TJ ≤ +125°C 40V 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) SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit Figure 1 VOUT Feedback Voltage VIN = 12V , ILOAD = 0.5A VOUT = 5V 0.5A ≤ ILOAD ≤ 3A, 6V ≤ VIN ≤ 40V VOUT = 5V VIN = 12V, ILOAD = 3A, VOUT = 5V VIN = 12V , ILOAD = 0.5A VOUT = 3.3V 0.5A ≤ ILOAD ≤ 3A, 6V ≤ VIN ≤ 40V VOUT = 3.3V VIN = 12V, ILOAD = 3A VIN = 12V , ILOAD = 0.5A VOUT = 5V 0.5A ≤ ILOAD ≤ 3A, 8V ≤ VIN ≤ 40V VOUT = 5V VIN = 12V, ILOAD = 3A VIN = 25V , ILOAD = 0.5A VOUT = 12V 0.5A ≤ ILOAD ≤ 3A, 15V ≤ VIN ≤ 40V VOUT = 12V VIN = 25V, ILOAD = 3A 1.230 1.217 1.243 1.230 1.193/1.180 1.267/1.280 82 V V(min) V(max) V V(min) V(max) % VOUT Feedback Voltage LM2576 Efficiency η SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3) Test Circuit Figure 1 VOUT Output Voltage 3.3 3.234 3.366 3.3 3.168/3.135 3.432/3.465 75 V V(min) V(max) V V(min) V(max) % VOUT Output Voltage LM2576-3.3 Efficiency η SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit Figure 1 VOUT Output Voltage 5.0 4.900 5.100 5.0 4.800/4.750 5.200/5.250 82 V V(min) V(max) V V(min) V(max) % VOUT Output Voltage LM2576-5.0 Efficiency η SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit Figure 1 VOUT Output Voltage 12 11.760 12.240 12 11.520/11.400 12.480/12.600 88 V V(min) V(max) V V(min) V(max) % VOUT Output Voltage LMLM2576-12 Efficiency η 4-122 October 1998 LM2576 Micrel Electrical Characteristics (continued) LM2576 Symbol Parameter Conditions Typ Limit (Note 2) Units (Limits) DEVICE PARAMETERS, ADJUSTABLE REGULATOR IB fO Feedback Bias Current VOUT = 5V 50 100/500 nA DEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORS Oscillator Frequency 52 47/42 58/63 Saturation Voltage Max Duty Cycle (ON) Current Limit IOUT = 3A (Note 4) (Note 5) Peak Current, tON ≤ 3µs (Note 4) 1.4 1.8/2.0 98 93 ICL 5.8 4.2/3.5 6.9/7.5 2 7.5 30 5 10 Standby Quiescent Current Thermal Resistance ON/OFF Pin = 5V (OFF) T,U Package, Junction to Ambient (Note 7) T,U Package, Junction to Ambient (Note 8) T,U Package, Junction to Case 50 200 65 45 2 kHz kHz (min) kHz (max) V V(max) % %(min) A A(min) A(max) mA(max) mA mA(max) mA mA(max) µA µA(max) °C/W VSAT DC IL Output Leakage Current VIN = 40V, (Note 6), (Note 6) Output = 0V Output = –1V Output = –1V IQ ISTBY θJA θJA θJC Quiescent Current (Note 6) 4 October 1998 4-123 LM2576 Micrel Electrical Characteristics (continued) LM2576 Symbol Parameter Conditions Typ Limit (Note 2) Units (Limits) ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS Test Circuit Figure 1 VIH VIL IIH IIL Note 1: ON/OFF Pin Logic Input Level ON /OFF Pin Logic Current VOUT = 0V VOUT = 5V ON /OFF Pin = 5V (OFF) ON/OFF Pin = 0V (ON) 1.4 1.2 4 2.2/2.4 1.0/0.8 30 V(min) V(max) µA µA(max) µA µA(max) 0.01 10 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. 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. 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. Output (pin 2) sourcing current. No diode, inductor or capacitor connected to output. Feedback (pin 4) removed from output and connected to 0V. Feedback (pin 4) removed from output and connected to 12V to force the output transistor OFF. 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. 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. Junction to ambient thermal resistance with approximately 1 square inch of pc board copper surrounding the leads. Additional copper will lower thermal resistance further. Note 2: Note 3: Note 4: Note 5: Note 6: Note 7: Note 8: Note 9: Typical Performance Characteristics Normalized Feedback Voltage* NORMALIZED FEEDBACK VOLTAGE (mV) Feedback Voltage vs Duty Cycle* 20 FEEDBACK VOLTAGE CHANGE (mV) 25 20 15 10 5 0 -5 -10 -15 -20 -25 -75 -50 -25 0 VIN = 12V ILOAD = 200mA Normalized to TJ = 25˚C ILOAD = 200 mA 15 10 5 0 -5 -10 -15 -20 0 20 40 60 80 100 DUTY CYCLE (%) VIN = 40V VIN = 7V 25 50 75 100 125 150 JUNCTION TEMPERATURE (˚C) * Adjustable version only 4-124 October 1998 LM2576 Micrel (Circuit of Figure 1) Typical Performance Characteristics (continued) Supply Current vs. Duty Cycle Supply Current 20 18 SUPPLY CURRENT (mA) Standby Quiescent Current STANDBY QUIESCENT CURRENT (µA) 16 14 12 10 8 6 4 0 10 20 30 SUPPLY CURRENT (mA) Measured at Ground Pin TJ = 25˚C VOUT = 5V 20.0 17.5 15.0 12.5 10.0 7.5 5.0 2.5 VIN from 7V to 40V 0 20 40 60 80 100 ILOAD = 200 mA 200 VIN = 40V 150 VON/OFF = 5V VIN = 12V 50 100 ILOAD to 1A 40 50 60 0 0 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (˚C) INPUT VOLTAGE (V) DUTY CYCLE (%) Current Limit 6.5 VIN = 12V SATURATION VOLTAGE (V) OUTPUT CURRENT (A) Switch Saturation Voltage 1.5 1.4 1.2 1.0 0.8 0.6 0.4 0.2 25˚C 150˚C EFFICIENCY (%) Efficiency 100 95 VOUT = 12V 1A 6.0 5.5 5.0 4.5 4.0 -75 -50 -25 0 -55˚C 90 85 80 75 70 65 60 1A 3A 0 5 200 mA 200 mA 3A VOUT = 3V 4 0 25 50 75 100 125 150 0 0.5 1.0 1.5 2.0 2.5 3.0 SWITCH CURRENT (A) 10 15 20 25 30 35 40 JUNCTION TEMPERATURE (˚C) INPUT VOLTAGE (V) Minimum Operating Voltage NORMALIZED FEEDBACK VOLTAGE (mV) Line Regulation Normalized to V IN = 10V VOUT = 5V ILOAD = 500mA TJ = 25 STANDBY QUIESCENT CURRENT (µA) Feedback Pin Current 100 75 50 25 0 -25 -50 -75 -100 -75 -50 -25 0 25 50 75 100 125 150 5.0 4.5 4.0 INPUT VOLTAGE (V) 14 12 10 8 6 4 2 0 -2 -4 -6 0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -75 -50 -25 0 VOUT = 1.23V ILOAD = 200 mA 25 50 75 100 125 150 5 10 15 20 25 30 JUNCTION TEMPERATURE (˚C) INPUT VOLTAGE (V) JUNCTION TEMPERATURE (˚C) Normalized Output Voltage 100 OUTPUT VOLTAGE CHANGE (mV) Oscillator Frequency +8 +6 NORMALIZED FREQUENCY (%) Dropout Voltage 2.0 INPUT-OUTPUT DIFFERENTIAL (V) 75 50 25 0 -25 -50 -75 VIN = 12V ILOAD = 200mA Normalized to TJ = 25˚C Normalized at 25˚C 1.5 ILOAD = 3A L1 = 330 µH +4 +2 0 -2 -4 --6 VIN = 40V ILOAD = 1A 1.0 0.5 ILOAD = 200 mA -100 -75 -50 -25 0 25 50 75 100 125 150 VIN = 12V -8 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (˚C) 0 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (˚C) JUNCTION TEMPERATURE (˚C) October 1998 4-125 LM2576 Micrel Typical Performance Characteristics (Circuit of Figure 1) Load Transient Response +100mV Output Voltage Change 0 -100mV 3A 2A 1A 0 100 µS/div. Output Current 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 4-126 October 1998 LM2576 Micrel Test Circuits and Layout Guidelines FEEDBACK +VIN 1 7V - 40V UNREGULATED DC INPUT + 100 µF CIN GND 3 ON/OFF 5 2 4 LM2575 OUTPUT L1 330 µH D1 MBR360 VOUT 5.00V + COUT 470µF R2 R1 L O A D 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.) FEEDBACK +VIN 1 7V - 40V UNREGULATED DC INPUT + 100 µF CIN GND 3 ON/OFF 5 2 4 LM2575-5.0 OUTPUT L1 330 µH D1 11DQ06 VOUT 5.00V + COUT 220µF L O A D 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.) 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. 4 Block Diagrams V IN FEEDBACK 1 4 3.1k INTERNAL REGULATOR ON/OFF 5 ON/OFF V IN 1 INTERNAL REGULATOR ON/OFF 5 ON/OFF FIXED GAIN ERROR AMP FIXED GAIN ERROR AMP COMPARATOR 3 AMP SWITCH FEEDBACK + 1.0k 4 + + - COMPARATOR 3 AMP SWITCH - + - DRIVER DRIVER 2 1.23V BAND-GAP REFERENCE OUTPUT 1.23V BAND-GAP REFERENCE 2 OUTPUT 52 kHz OSCILLATOR RESET THERMAL SHUTDOWN CURRENT LIMIT 3 GND 52 kHz OSCILLATOR RESET THERMAL SHUTDOWN CURRENT LIMIT 3 GND Note: Pin numbers are for the TO-220 package Fixed Regulator Adjustable Regulator October 1998 4-127