LM2576-5.0BT

4-120 October 1998 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-by- cycle current limiting and thermal shutdown for full protection under fault conditions. 870 20 Typical Applications 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 R2 R1 7V–40V Unregulated DC Input LM2576 + CIN 100µF +VIN 1 3 Gnd 5 On/Off 2 Output 4 Feedback L1 100µH + D1 1N5822 COUT 1000µF R2 3.09k R1 1k VOUT = 1.23 1 +( ) +5V, 3A Regulated Output Note: Pin numbers are for TO-220 Package 7V–40V Unregulated DC Input LM2576-5.0 + CIN 100µF +VIN 1 3 Gnd 5 On/Off 2 Output 4 Feedback L1 100µH + D1 1N5822 COUT 1000µF +5V, 3A Regulated Output Note: Pin numbers are for TO-220 Package Fixed Regulator in Typical Application Adjustable Regulator in Fixed Output Application October 1998 4-121 LM2576 Micrel 4 Part Number‡ Temperature Range Package LM2576BT*† –40°C to +85°C 5-lead TO-220 LM2576-3.3BT† –40°C to +85°C 5-lead TO-220 LM2576-5.0BT† –40°C to +85°C 5-lead TO-220 LM2576-12BT† –40°C to +85°C 5-lead TO-220 LM2576BU* –40°C to +85°C 5-lead TO-263 LM2576-3.3BU –40°C to +85°C 5-lead TO-263 LM2576-5.0BU –40°C to +85°C 5-lead TO-263 LM2576-12BU –40°C to +85°C 5-lead TO-263 * Adjustable output regulators. † Contact factory for bent or staggered leads option. Pin Configurations GND 5- ON/OFF 4- FEEDBACK 3- GROUND 2- OUTPUT 1- VIN 5-LEAD TO-263 (U) GND 5- ON/OFF 4- FEEDBACK 3- GROUND 2- OUTPUT 1- VIN 5-LEAD TO-220 (T) Ordering Information 4-122 October 1998 LM2576 Micrel 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 Units (Note 2) (Limits) SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit Figure 1 VOUT Feedback Voltage VIN = 12V , ILOAD = 0.5A 1.230 V VOUT = 5V 1.217 V(min) 1.243 V(max) VOUT Feedback Voltage 0.5A ≤ ILOAD ≤ 3A, 6V ≤ VIN ≤ 40V 1.230 V LM2576 VOUT = 5V 1.193/1.180 V(min) 1.267/1.280 V(max) 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 3.3 V VOUT = 3.3V 3.234 V(min) 3.366 V(max) VOUT Output Voltage 0.5A ≤ ILOAD ≤ 3A, 6V ≤ VIN ≤ 40V 3.3 V LM2576-3.3 VOUT = 3.3V 3.168/3.135 V(min) 3.432/3.465 V(max) η Efficiency VIN = 12V, ILOAD = 3A 75 % SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit Figure 1 VOUT Output Voltage VIN = 12V , ILOAD = 0.5A 5.0 V VOUT = 5V 4.900 V(min) 5.100 V(max) VOUT Output Voltage 0.5A ≤ ILOAD ≤ 3A, 8V ≤ VIN ≤ 40V 5.0 V LM2576-5.0 VOUT = 5V 4.800/4.750 V(min) 5.200/5.250 V(max) η Efficiency VIN = 12V, ILOAD = 3A 82 % SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit Figure 1 VOUT Output Voltage VIN = 25V , ILOAD = 0.5A 12 V VOUT = 12V 11.760 V(min) 12.240 V(max) VOUT Output Voltage 0.5A ≤ ILOAD ≤ 3A, 15V ≤ VIN ≤ 40V 12 V LMLM2576-12 VOUT = 12V 11.520/11.400 V(min) 12.480/12.600 V(max) η Efficiency VIN = 25V, ILOAD = 3A 88 % Absolute Maximum Ratings (Note 1) Maximum Supply Voltage 45V ON/OFF Pin Input Voltage –0.3V ≤ V ≤ +40V Output Voltage to Ground (Steady State) –1V Power Dissipation Internally Limited Storage Temperature Range –65°C to +150°C Minimum ESD Rating C = 100pF, R = 1.5kΩ 2 kV FB Pin 1 kV Lead Temperature (soldering, 10 sec.) 260°C Maximum Junction Temperature 150°C Operating Ratings Temperature Range –40°C ≤ TJ ≤ +125°C Supply Voltage 40V October 1998 4-123 LM2576 Micrel 4 Electrical Characteristics (continued) LM2576 Units Symbol Parameter Conditions Typ Limit (Limits) (Note 2) DEVICE PARAMETERS, ADJUSTABLE REGULATOR IB Feedback Bias Current VOUT = 5V 50 100/500 nA DEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORS fO Oscillator Frequency 52 kHz 47/42 kHz (min) 58/63 kHz (max) VSAT Saturation Voltage IOUT = 3A (Note 4) 1.4 V 1.8/2.0 V(max) DC Max Duty Cycle (ON) (Note 5) 98 % 93 %(min) ICL Current Limit Peak Current, tON ≤ 3µs (Note 4) 5.8 A 4.2/3.5 A(min) 6.9/7.5 A(max) IL Output Leakage Current VIN = 40V, (Note 6), Output = 0V 2 mA(max) Output = –1V 7.5 mA (Note 6) Output = –1V 30 mA(max) IQ Quiescent Current (Note 6) 5 mA 10 mA(max) ISTBY Standby Quiescent ON/OFF Pin = 5V (OFF) 50 µA Current 200 µA(max) θJA Thermal Resistance T,U Package, Junction to Ambient (Note 7) 65 °C/W θJA T,U Package, Junction to Ambient (Note 8) 45 θJC T,U Package, Junction to Case 2 4-124 October 1998 LM2576 Micrel Electrical Characteristics (continued) LM2576 Units Symbol Parameter Conditions Typ Limit (Limits) (Note 2) ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS Test Circuit Figure 1 VIH ON/OFF Pin Logic VOUT = 0V 1.4 2.2/2.4 V(min) VIL Input Level VOUT = 5V 1.2 1.0/0.8 V(max) IIH ON /OFF Pin Logic ON /OFF Pin = 5V (OFF) 4 µA Current 30 µA(max) IIL ON/OFF Pin = 0V (ON) 0.01 µA 10 µA(max) 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 Normalized Feedback Voltage* JUNCTION TEMPERATURE (˚C) N O RM AL IZ ED F EE DB AC K VO LT AG E (m V) 25 20 15 10 5 0 -5 -10 -15 -20 -25 -75 -50 -25 0 25 50 75 100125150 VIN = 12V ILOAD = 200mA Normalized to TJ = 25˚C Feedback Voltage vs Duty Cycle* DUTY CYCLE (%) FE ED B A CK V O LT AG E CH AN G E (m V) 20 15 10 5 0 -5 -10 -15 -20 ILOAD = 200 mA VIN = 40V VIN = 7V 0 20 40 60 80 100 * Adjustable version only October 1998 4-125 LM2576 Micrel 4 Typical Performance Characteristics (continued) (Circuit of Figure 1) Supply Current INPUT VOLTAGE (V) SU PP LY C UR RE NT (m A) 20 Measured at Ground Pin TJ = 25˚C VOUT = 5V 18 16 14 12 10 8 6 4 0 10 20 30 40 50 60 ILOAD to 1A Supply Current vs. Duty Cycle DUTY CYCLE (%) 20.0 17.5 15.0 12.5 10.0 7.5 5.0 2.5 0 0 20 40 60 80 100 VIN from 7V to 40V ILOAD = 200 mA SU PP LY C UR RE NT (m A) JUNCTION TEMPERATURE (˚C) 200 150 100 50 0 -75 VIN = 12V ST AN DB Y QU IE SC EN T CU RR EN T (µ A) Standby Quiescent Current VIN = 40V -50 -25 0 25 50 75 100 125150 Minimum Operating Voltage JUNCTION TEMPERATURE (˚C) 5.0 ILOAD = 200 mA IN PU T VO LT AG E (V ) Line Regulation INPUT VOLTAGE (V) 14 0 N O RM AL IZ ED F EE DB AC K VO LT AG E (m V) JUNCTION TEMPERATURE (˚C) 100 -100 -75 ST AN DB Y QU IE SC EN T CU RR EN T (µ A) Feedback Pin Current -50 -25 0 25 50 75 100 125150 VOUT = 1.23V 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -75 -50 -25 0 25 50 75 100125150 12 10 8 6 4 2 0 -2 -4 -6 5 10 15 20 25 30 75 50 25 0 -25 -50 -75 JUNCTION TEMPERATURE (˚C) +8 -8 -75 N O RM AL IZ ED F RE QU EN CY (% ) Oscillator Frequency -50 -25 0 25 50 75 100125150 +6 +4 +2 0 -2 -4 --6 VIN = 12V VIN = 40V Normalized at 25˚C Normalized to VIN = 10V VOUT = 5V ILOAD = 500mA TJ = 25 VON/OFF = 5V Normalized Output Voltage JUNCTION TEMPERATURE (˚C) O UT PU T VO LT AG E CH AN G E (m V) 100 75 50 25 0 -25 -50 -75 -100 -75 -50 -25 0 25 50 75 100125150 VIN = 12V ILOAD = 200mA Normalized to TJ = 25˚C Current Limit JUNCTION TEMPERATURE (˚C) 6.5 6.0 5.5 5.0 4.5 4.0 -75 VIN = 12V O UT PU T CU RR EN T (A ) Switch Saturation Voltage SWITCH CURRENT (A) 1.5 -55˚C 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0 SA TU RA TI O N VO LT AG E (V ) INPUT VOLTAGE (V) 100 EF FI CI EN CY (% ) Efficiency VOUT = 12V -50 -25 0 25 50 75 100125150 0.5 1.0 1.5 2.0 2.5 3.0 25˚C 150˚C 95 90 85 80 75 70 65 60 200 mA 200 mA VOUT = 3V 1A 3A 1A 3A 0 5 10 15 20 25 30 35 40 Dropout Voltage JUNCTION TEMPERATURE (˚C) IN PU T- O UT PU T DI FF ER EN TI AL (V ) 2.0 -75 -50 -25 0 25 50 75 100125150 ILOAD = 3A L1 = 330 µH ILOAD = 1A ILOAD = 200 mA 1.5 1.0 0.5 0 4-126 October 1998 LM2576 Micrel 100 µS/div. Load Transient Response +100mV 0 -100mV Output Voltage Change 3A 2A 1A 0 Output Current 50V 0 4A 2A 0 4A 2A 0 A B C D 5 µS/div. Switching Waveforms 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 VOUT = 5V VIN = 45V Typical Performance Characteristics (Circuit of Figure 1) October 1998 4-127 LM2576 Micrel 4 LM2575 + 100 µF +VIN 1 3GND 5ON/OFF 2 OUTPUT 4 FEEDBACK L1 330 µH + D1 MBR360 COUT 470µF R2 R1 VOUT 5.00V 7V - 40V UNREGULATED DC INPUT CIN 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.) LM2575-5.0 + 100 µF +VIN 1 3GND 5ON/OFF 2 OUTPUT 4 FEEDBACK L1 330 µH + D1 11DQ06 COUT 220µF VOUT 5.00V Note: Pin numbers are for TO-220 Package 7V - 40V UNREGULATED DC INPUT CIN 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 ON/OFF COMPARATOR FIXED GAIN ERROR AMP 3 AMP SWITCH OUTPUT DRIVER + - + - VIN FEED- BACK 1.23V BAND-GAP REFERENCE 52 kHz OSCILLATOR RESET THERMAL SHUTDOWN CURRENT LIMIT 5 2 3 1 Note: Pin numbers are for the TO-220 package INTERNAL REGULATOR ON/OFF GND ON/OFF COMPARATOR FIXED GAIN ERROR AMP 3 AMP SWITCH OUTPUT DRIVER + - + - VIN FEED- BACK 1.23V BAND-GAP REFERENCE 52 kHz OSCILLATOR RESET THERMAL SHUTDOWN CURRENT LIMIT 5 2 3 1 4 INTERNAL REGULATOR ON/OFF GND 3.1k 1.0k 4 Block Diagrams 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. Fixed Regulator Adjustable Regulator Test Circuits and Layout Guidelines Figure 1.