Milvel. LM2576 52kHz Simple 3A Buck Voltage Regulator Generali 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, 12V, or 15V fixed output. Adjustable versions have an output voltage range from 1.23 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 interna! 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. Astandard 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 200pA standby current. The output switch includes cycle-by- cycle current limiting and thermal shutdown for full protection under fault conditions. Features * 3.3V, 5V, 12V, 15V, 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 * S2kHz fixed frequency internal oscillator + Low power standby mode I, typically < 200A * 80% efficiency (adjustable version typically > 80%) + Uses readily available standard inductors * Thermal shutdown and current limit protection + 100% electrical thermal timit 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 5V. 3A 4 toV, DC Input 4 Feedback Regulated TW |4M2576-5-9| output Lt Output Cc +] 3 5 2 t+ s00uF Gnd] On/Off Tl Cour 4000uF Note: Pin numbers are for TO-220 Package Fixed Regulator in Typical Application 7V-40V Unregulated 5V. 3A 4 dback +5V, DC Input 4 Feedbac Regulated Vin LM2576 Output Li Output + 3 ay 2 + R2 3.09k Cin Gnd] On/Off Court [sooo Al 4k Note: Pin numbers are for TO-220 Package Vour = 1.23 ( +2) Adjustable Reguiator in Fixed Output Application 4-120 1997LM2576 Ordering Information Micrel Part Number* Temperature Range Package LM2576BT* 40C to +85C 5-lead TO-220 LM2576-3.3BTt 40C to +85C 5-lead TO-220 LM2576-5.0BT* 40C to +85C 5-lead TO-220 LM2576-12BTt ~40C to +85C 5-lead TO-220 LM2576BU* 40C to +85C 5-lead TO-263 LM2576-3.3BU 40C to +85C 5-lead TO-263 LM2576-5.0BU 40C to +85C 5-lead TO-263 LM2576-12BU ~40C to +85C 5-lead TO-263 * Adjustable output regulators. t Contact factory for bent or staggered leads option. Pin Configurations 5-LEAD TO-220 (T) GND O wo G) 5- ON/OFF 4- FEEDBACK OUND OUTPUT GND 5-LEAD TO-263 (U) 5- ON/OFF 4- FEEDBACK 3- GROUND of== 2- OUTPUT Hue 1- VIN 1997 4-121LM2576 Micrel Absolute Maximum Ratings (Note 1) Operating Ratings Maximum Supply Voltage 45V Temperature Range 40C S$ Ts 4125C ON/OFF Pin Input Voltage 0.3V <V<+40V Supply Voltage 40V Output Voltage to Ground (Steady State) -1V Power Dissipation Storage Temperature Range Minimum ESD Rating C = 100pF, R = 1.5kQ FB Pin Lead Temperature (soldering, 10 sec.) Maximum Junction Temperature Internally Limited ~65C to +150C 2kV TkV 260C 150C. Electrical Characteristics Specifications with standard typeface are for T, = 25C, and those with boldface type apply over full Operating Temperature Range. Unless otherwise specified, V,, = 12V, and | gap = 500mA. LM2576 Symboi | Parameter Conditions Typ Limit Units (Note 2) (Limits) SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit Figure 1 Vout Feedback Voltage Vin = 12V. boap = 0.5A 1.230 v Vout = 1.217 Vimin) 1.243 Vimax) Vour Feedback Voltage 0.5A < li gap $ 3A, BV S$ Vin, $ 40V 1.230 V LM2576 Vout = 5V 1.193/1.180 V(min) 1.267/1,280 Vi{max) n Efficiency Vin = 12V, ILoap = 3A: Vour = 5V 82 % SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3) Test Circuit Figure 7 Vour Output Voltage Vin = 12V, fLoap = 0.5A 3.3 v Vout = 3.234 V(min) 3.366 V(max) Vout Output Voltage 0.5A < | oap $ 3A; 6V < Vin, < 40V 3.3 Vv LM2576-3.3 Vout = 3.3V 3.168/3.135 V(min) 3.432/3.465 (max) n Efficiency Vin = 12V, lLoap = 3A 75 % SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit Figure 7 Vout Output Voltage Vin = 12V, Loap = 0.5A 5.0 v Vout = 4.900 V(min) 5.100 V(max)} Vout Output Voltage 0.5A = lLoap 3A, BV < Viy = 40V 5.0 Vv LM2576-5.0 Vout = 5V 4.800/4.750 Vimin) .200/5.250 V(max) n Efficiency Vin = 12, lLoap = 3A 82 % SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit Figure 1 Vout Output Voltage Vin = 25V . Loap = 0.5A 12 v Vout = 12 11.760 Vimin) 12.240 V(max) Vout Output Voltage 0.54 < lignan < 3A, 15V < Vin < 40V 12 Vv LMLM2576-12 Vout = 12V 11.520/11.400 (min) 12.480/12.600 V(max) n Efficiency Vin = 259, ILoap = 3A 88 % 4-122 1997LM2576 Micrel Electrical Characteristics (continued) LM2576 Units Symboi | Parameter Conditions Typ Limit (Limits) (Note 2) SYSTEM PARAMETERS, 15V REGULATORS (Note 3) Test Circuit Figure 7 Vout Output Voltage Vin = 30V , loap = 0-54 15 Vv Vout = 1 14.700 V(min} 15.300 V(max) Vout Output Voltage 0.54 < logy $ 3A, 18V < Vix, < 40V 15 V LM2576-15 Vout = 16V 14.400/14.250 V(min) 15.600/15.750 V{max) n Efficiency Vin = 30V, ligap = 3A 88 % DEVICE PARAMETERS, ADJUSTABLE REGULATOR lp 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 lout = 34 (Note 4) 1.4 v 1.8/2.0 V(max) DC Max Duty Cycle (ON) (Note 5) 98 % 93 %{min) lot Current Limit Peak Current, toy < 3us (Note 4) 5.8 A 4.2/3.5 A(min) 6.9/7.5 A(max) I Output Leakage Current} V,, = 40V, (Note 6), Output = OV 2 mA(max)} Output = -1V 7.5 mA (Note 6) Output = -1V 30 mA(max) lg Quiescent Current (Note 6) 5 mA 10 mA(max} lstpy Standby Quiescent ON/OFF Pin = 5V (OFF) 50 BA Current 200 pA(max) Ou0 Thermal Resistance T,U Package, Junction to Ambient (Note 7)} 65 CW B50 T,U Package, Junction to Ambient (Note 8)} 45 856 T,U Package, Junction to Case 2 1997 4-123LM2576 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 Ving ON/OFF Pin Logic Vout = OV 1.4 2.2/2.4 Vimin) Vib Input Level Vout = 5V 1.2 1.0/0.8 Vimax) lag ON /OFF Pin Logic ON /OFF Pin = 5V (OFF) 4 yA Current 30 pA(max) he ON/OFF Pin = OV (ON) 0.01 pA 10 pA(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 (bald 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 7 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 OV. 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 Feedback Voltage* vs Duty Cycle* 25 Ving = 20 iN Loap=200mA Normaiized to T, = 25C ILOAD = mA 5 -10 NORMALIZED FEEDBACK VOLTAGE {mV} FEEDBACK VOLTAGE CHANGE (mV) 15 -20 25 -76 -50-25 Q 25 50 75 100125150 o 20 40 60 80 6100 JUNCTION TEMPERATURE ('C} GUTY CYCLE (%) * Adjustable version only 4-124 1997LM2576 Micrel Typical Performance Characteristics (continued) (Circuit of Figure 1) Supply Current Standby Supply Current vs. Duty Cycle Quiescent Current 200 at _ Ground S z 16 Your =5 = 150 5 14 5 3 12 & 100 oO Qo 3 10 Z 7 Loap= 2 oa a hoab 2 & 50 from 7V to 40V b 4 o 10 20 300 640065060 oO 20 40 60 80 100 -$0 -25 0 25 50 75100 125150 INPUT VOLTAGE () DUTY CYCLE (%) JUNCTION TEMPERATURE (C) Switch Current Limit Saturation Voltage Efficiency 65 1 1. z = = 8 Boss e 8 7 5 E ; 0. y 4s a 40 Qo 60 -75 -50 -25 0 25 50 75 100125150 0 05 106 #15 20 25 30 0 5S 10 15 20 25 30 35 40 JUNCTION TEMPERATURE (C) SWITCH CURRENT {A) INPUT VOLTAGE (} Minimum Operating Voltage Line Regulation Feedback Pin Current s = E Normatized to Vjpy = 10V 3 g Vout 25V | 5 s z LLoap = 500mA = a S Ty =25 2 g x < 3 2 < a 8 a 2 1 3 > Vout = 1.23V 4 2 Loap = 200 mA 3 a oO a z -75 -50 -25 0 25 50 75 100125150 o 5 10 15 2 2 30 -75 80 -25 0 25 50 75 100 125150 JUNCTION TEMPERATURE ('C) INPUT VOLTAGE (V} JUNCTION TEMPERATURE ("C) Normalized Output Voltage Oscillator Frequency Dropout Voltage 100 VIN = 12 Normalized 7 a g 7 KoaD = 200mA z Loap Li = 330 = Normatized to Ty = 25C. = 1 3% 5 = 25 z & hoap= : 3 i S < & 5 a 25 8 E > g = 5-60 2 : hoap= E z 3 75 g 6 Vipy = 12 s -1 5 -50 -25 0 25 50 75 100125150 -75 50-25 0 25 50 75 100125150 -75 -50-25 0 25 50 75 100125150 JUNCTION TEMPERATURE ((C} JUNCTION TEMPERATURE (C) JUNCTION TEMPERATURE ('C) 1997 4-125LM2576 Micre! Typical Performance Characteristics (circuit of Figure 1) Load Transient Response + Output opaage Output Current 100 pSvdiv. Switching Waveforms 50V A 0 4A 8 2A 0 aA C1 2a Qo m4 5 pS/div. Your =5 Vig = 45V A: Output pin voltage 50Vidiv B: Output pin current 2A/div C: Inductor current 2A/div D: Output ripple voltage 50 mV/div., AC coupled Horizontal Time Base: SyS/div 4-126 1997LM2576 Micrel Test Circuits and Layout Guidelines FEEDBACK 4 LM2575 uy Vout OUTPUT 5.00V 068... 4Vin Cy 100pF, 75V Aluminum Electrolytic Cour 470pF, 15V Aluminum Electrolytic Dt - Schottky, MBR360 L Lt 330pH, At5- 0926 (AIE) 0 Rt ~ 1k, 0.019 A R2 ~ 3.065k, Cor% D 5-pin TO-220 socket2936 (Loranger Mig. Co.) 4-pin TO-3 socket8112-AG7 (Augat Inc.) 330uH fy < I COUT < a > = 470uF = : 7V - 40V UNREGULATED + DC INPUT D1 MBA360 FEEDBACK +Vin LM2575-5.0 output your, Cin 100yF, 75V Aluminum Electrolytic . cout ~~ 330yF, 15V Aluminum Electrolytic Schottky, 110Q06 cy = {OBE 445-1 0086 (AE socket2! i 100 pF + GND G3 ON/OFF [5 S-pin TO. Loranger | Mig. Co.) 4-pin TO-3 sacket$112-A 7V - 40V UNREGULATED DC INPUT 7 (Augat inc. Gin oo Note: Pin numbers are far TO-220 Package Figure 1. Asin any switching regulator, layout is very important. Rapidly switching currents associated with wiring inductance generate voitage 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 ON/OFF INTERNAL REGULATOR, COMPARATOR: FIXED GAIN ERROR AMP 2] OUTPUT 1.23V | SANO-GAP 52 kHz BAND-GAP. $2 kHz REFERENCG | OSCILLATOR REFERENCE] OSCILLATOR SHUTDOWN] UNIT 3] anp Note: Pin numbers are for the TO-220 package Fixed Regulator Adjustable Regulator 1997 4-127