LM2575 52kHz Simple 1A Buck Voltage Regulator General Description 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, or 15V 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. Astandard 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 200uA 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 voitage 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 | typically < 2000A * 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 7V40V 7V~40V Unregulated Unregulated Vo41A 4 Fi +5V,1A 4 Fi ck +5V, DC Input 4 gedback Regulated DC Input 4 seca Regulated +Vin LM2575-5.0 Output L1 Output +Vin LM2575 Output ul Output | ro + 30 TC? + + a) By + R2 3.09k N Gnd | On/Off a N Gnd] On/Off D4 100uF so 100pF 15822 [a Ri 1k Note: Pin numbers are for TO-220 Package Fixed Regulator in Typical Application Note: Pin numbers are for TO-220 Package Vour= 1.23 (: + Be) Adjustable Regulator in Fixed Output Application 4-29LM2575 Micrel Ordering Information Part Number* Temperature Range Package LM2575BN 40C to +85 C 16-pin Plastic DIP LM2575-3.3BN 40C to +85 C 16-pin Plastic DIP LM2575-5.0BN ~40C to +85 C 16-pin Plastic DIP LM2575-12BN ~40C to +85 C 16-pin Plastic DIP LM2575-15BN 40C to +85 C 16-pin Plastic DIP LM2575BWM* 40C to +85C 24-pin Wide SOIC LM2575-3.3BWM 40C to +85C 24-pin Wide SOIC LM2575-5.0BWM 40C to +85C 24-pin Wide SOIC LM2575-12BWM 40C to +85C 24-pin Wide SOIC LM2575-15BWM ~40C to +85C 24-pin Wide SOIC LM2575BT*t 40C to +85C 5-lead TO-220 LM2575-3.3BT* ~40C to +85C 5-lead TO-220 LM2575-5.0BT* 40C to +85C 5-lead TO-220 LM2575-12BTt 40C to +85C 5-lead TO-220 LM2575-15BTt 40C to +85C 5-lead TO-220 LM2575BU* 40C to +85C 5-lead TO-263 LM2575-3.3BU 40C to +85C 5-lead TO-263 LM2575-5.0BU 40C to +85C 5-lead TO-263 LM2575-12BU 40C to +85C 5-lead TO-263 LM2575-15BU 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 5-LEAD TO-263 (U) GND 5- ON/OFF 5- ON/OFF 4- FEEDBACK Fe 4- FEEDBACK O 3- GROUND Fs= 3- GROUN 2- OUTPUT => 3. OUTPUT 1- VIN 1- Vin 24-LEAD SOIC (WM) pwrenpt}e ~~ [L24nc 16-LEAD DIP (N) no-24 L238 NC NCT} VIN no 4 121 NC 2 15 5 20 NC. =- NC No =4 pe! NC ouTPuT3 14 GND nc& BERN No HS GND rp 18 OUTPUT GND }2 GND sic anp 84 HZ OUTPUT NC~- ig GNP Nco2 16 NG Fe FNC ON/OFF 194 p15 vin NCH + ON/OFF noe p14 in pwr enp 12] 113. uc 4-30LM2575 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 = 1.5kQ FB Pin Lead Temperature (soldering, 10 sec.) Maximum Junction Temperature Operating R atings 45V Temperature Range -0.38V < Vs +40V Supply Voltage -1V Internally Limited 65C to +150C 2kV 1kVv 260C 150C Micrel 40C < T,<$+125C 40V 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 = 200mA. LM2575 Symbol | Parameter Conditions Typ Limit Units (Note 2) (Limits) SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit Figure 1 Vout Feedback Voltage Vin = 12V, lLoap = 0.24 1.230 Vv Vout =5 1.217 Vimin) 1.243 V(max) Vout Feedback Voltage 0.2A $ l.oap $ 1A, BV < Vix < 40V 1.230 Vv LM2575 Vout = 5V 1.193/1.180 V(min) 1.267/1.280 V(max) n Efficiency Vin = 42V, lLoap = 14, Voyy = SV 82 % SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3) Test Circuit Figure 7 Vout Output Voltage Vin = 12V , ILoap = 0.2A 3.3 Vv Vout = 3.3V 3.234 V(min) 3.366 V(max) Vout Output Voltage 0.24 < loap S 1A, BV S Vin $ 40V 3.3 Vv LM2575-3.3 Vout = 3.3V 3.168/3.135 V(min) 3.432/3.465 Vv(max) n Efficiency Vin = 12, loan = 1A 75 % SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit Figure 1 Vout Output Voltage Vin = 12V, lLoap = 9.2A 5.0 Vv Vout = 4.900 V(min) 5.100 V(mnax) Vout Output Voltage 0.2A <I gap < 1A, BV s Vin < 40V 5.0 Vv LM2575-5.0 Vout = 5V 4.800/4.750 V(min) 5.200/5.250 V(max) n Efficiency Vin = 12. ILoan = 1A 82 % SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit Figure 1 Vout Output Voltage Vin = 25V , Loap = 0.24 12 Vv Vout = 12V 11.760 V(min) 12.240 V(max) Vout Output Voltage 0.2A lL oan $ 1A, 15V S Vin, < 40V 12 Vv LM2575-12 Vout = 12V 11.520/11.400 V{min) 12.480/12.600 V(max) n Efficiency Vin = 25V. Ioan = 1A 88 % 4-31LM2575 Electrical Characteristics (continued) Micrel LM2575 Units Symbol | Parameter Conditions Typ Limit (Limits) (Note 2) SYSTEM PARAMETERS, 15V REGULATORS (Note 3) Test Circuit Figure 1 Vout Output Voltage Vin = 30V , Ioan = 0.2A 15 Vv Vout = 14.700 V(min) 15.300 V(max) Vout Output Voltage 0.2A loan S$ 1A, 18V < Vix S$ 40V 15 Vv LM2575-15 Vout = 15V 14.400/14.250 V(min) 15.600/15.750 V(max)} n Efficiency Vin = 30V, ILoap = 14 88 % DEVICE PARAMETERS, ADJUSTABLE REGULATOR lp Feedback Bias Current | Voy = 5V | 50 | 100/500 nA DEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORS fo Oscillator Frequency 2 kHz 47/42 kHz (min) 58/63 kHz (max) Voat Saturation Voltage loyt = 14 (Note 4) 0.9 Vv 1.2/1.4 V(max) DC Max Duty Cycle (ON) (Note 5) 98 % 93 %(min) let Current Limit Peak Current, tony S$ Sus (Note 4) 2.2 A 1.7/1.3 A(min) 3.0/3.2 A(max) IL Output Leakage Current) Vj, = 40V, (Note 6), Output = OV 2 mA(max) Output = -1V 75 mA (Note 6) Output =-1V 30 mA(max) lg Quiescent Current (Note 6) 5 mA 10 mA(max) Istpy Standby Quiescent ON/OFF Pin = 5V (OFF) 50 HA Current 200 HA(max) Bya Thermal Resistance T Package, Junction to Ambient (Note 7) 65 CiW Bua T Package, Junction to Ambient (Note 8) 45 83c T Package, Junction to Case 2 Gyn N Package, Junction to Ambient (Note 9) 85 Oya WM Package, Junction to Amb. (Note 9) 100 4-32LM2575 Electrical Characteristics (continued) LM2575 Units Symbol | Parameter Conditions Typ Limit (Limits) (Note 2) ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS Test Circuit Figure 1 Vin ON/OFF Pin Logic Vout = OV 1.4 2.2/2.4 Vimin) Vit Input Level Vout = 5V 1.2 1.0/0.8 V(max) le ON /OFF Pin Logic ON /OFF Pin = 5V (OFF} 4 pA Current 30 yA(max) lie ON/OFF Pin = 0V (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 (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 17 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 pe board copper surrounding the leads. Additional copper will lower thermal resistance further. Typical Performance Characteristics Normalized Feedback Voltage Feedback Voltage* vs Duty Cycle* 'LoAD = 200 mA Vin = 124 ILoap = 200mA Normalized to Ty = 25C Vig = NORMALIZED FEEDBACK VOLTAGE (mV) FEEDBACK VOLTAGE CHANGE (mv) +2 5 -75 -50 -25 0 25 50 75 100125150 0 20 40 60 60 100 JUNCTION TEMPERATURE ('C) DUTY CYCLE (*) * Adjustable version only 4-33 MicrelLM2575 Typical Performance Characteristics (continued) (Circuit of Figure 1) OUTPUT CURRENT (A) SUPPLY CURRENT (mA) INPUT VOLTAGE (V) OUTPUT VOLTAGE CHANGE (mv} Supply Current at Ground Ty = 28C Vout = 5V o 10 20 30 40 50 60 INPUT VOLTAGE (V)} Current Limit 0 -75 -60-25 0 26 50 75100125 150 JUNCTION TEMPERATURE (C) Minimum Operating Voltage Vout = 1.23 Loap = 200 mA 0 -75 -50 -25 Q 25 50 75 100125150 JUNCTION TEMPERATURE (C) Normalized Output Voltage 100 VIN = 12V 75 ILOAD = 200mA 50 Normalized to Ty = 25C. 25 0 LL | 25 -50 75 -100 -75 -50 -25 0 265 50 75 100125150 JUNCTION TEMPERATURE (C) SUPPLY CURRENT (mA} SATURATION VOLTAGE (V) NORMALIZED FEEDBACK VOLTAGE {mV} NORMALIZED FREQUENCY (%) 1.2 10 a 2 6 Supply Current vs. Duty Cycle Loap = 200 Q 20 DUTY CYCLE (%) Switch Saturation Voltage Vin from 7V to 40V 40 60 BO 100 (NPUT VOLTAGE () Oscillator Frequency Normalized at VIN = 0 02 04 06 08 10 SWITCH CURRENT (A) Line Regulation Normalized to Vip) = 10V jormalized to = lVour=3 ao] LYourt = } | Loap = 500mA Ty =25 y 0 5 10 15 25 30 Vin = 12 +75 -60-25 0 25 50 75 100125150 JUNCTION TEMPERATURE (C) STANDBY QUIESCENT CURRENT (uA) EFFICIENCY (%@) STANDBY QUIESCENT CURRENT (uA) INPUT-OUTPUT DIFFERENTIAL (V) Standby Quiescent Current VYonrorr = V Q -75 -50 -25 0 25 50 75 100 125150 JUNCTION TEMPERATURE (C) Efficiency 100 a Yout = 4 2 o a on & Your = oe a a a 60 0 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V) Feedback Pin Current 100 75 50 25 -100 -75 -50 -25 0 25 50 75100 125150 JUNCTION TEMPERATURE (C) Dropout Voltage A = RIND = ILOAD= IND Loap = 200 mA Qo -75 -50 -25 0 25 50 75100125150 JUNCTION TEMPERATURE (C) Micrel 4-34LM2575 Micrel Typical Performance Characteristics (circuit of Figure 1) Load Transient Response +100mV Output Voltage Change -100mVv 1.0A 0.5A 9 Output Current 100pS/div. Vout = 5V Test Circuits and Layout Guidelines Switching Waveforms A fw | { Vout = 5 Vin = 20V B a 1A 0 1A 5A 0 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 Horizontal Time Base: Sys/div FEEDBACK 4 LM2575 ut vour, Cin 100pF, 75V Aluminum Electrolytic OUTPUT Cout 470pF, 15V Aluminum Electrolytic D1 Schottky, MBR360 UNREGULATED + 330 HH R2 L yt _ S30nH 5-0926 (AIE) 4 _ Me! 70 DG INPUT D1 =F 470uF 8 R2 3.085k, 0.01% MBR360. at D 5-pin TO-220 socket2936 (Loranger Mfg. Co.} 4-pin TO-3 sockel8112-AG7 (Augat Inc.) oe FEEDBACK Vout 41 Ciy ~ 100pF. 75V Aluminum Electrolytic OUTPUT 5.00 Cout 330pF, 15V Aluminum Electrolytic Di Schottky. MBR360 7V - 40V 330 LH ff 100 UF " + Lt 330uH, 415-0926 (AIE} UNREGULATED GNOY/3 ON/OFF] 5 ab Son 4 5-pin TO-220 socket2936 (Loranger Mig. Co.) Cin 22011 A 4-pin TO-3 socket8112-AG7 (Augat Inc.) D Note: Pin numbers are for TO-220 Package Figure 1. Asin 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 Wn INTERNAL 7 REGULATOR INTERNAL REGULATOR ON-OFF MN F.XED GSIN ERROR AME FIXED GAIN ERRCR AMP. FEED- BACK 1 AMP SWITCH BAN3-GAP, REFERENCE THERMAL SHUTDOWN, CURRENT LIMIT GAP REFERENCE| THERMAL SHUTDOWN 52 kHe 2 kHz OSCILLATOR OSC LLATOR Rote: Pin qumbers are for tne TO-229 package Fixed Regulator Adjustable Regulator 4-35