LM2574 52kHz Simple 0.5A Buck Voltage Regulator General Description The LM2574 family is a series of easy to use fixed and adjustable switching voltage regulators. The M2574 con- tains all of the active circuitry necessary to construct a stepdown (buck) switching regulator and requires a minimum of external components. The LM2574 is available in 3.3V, 5V, 12V, and 15V fixed output versions, or an adjustable version with an output voltage range of 1.23V to37V. Output voltage is guaranteed to t4% for specified input and load conditions. The LM2574 can supply 0.5A while maintaining excellent line and load regulation. The output switch includes cycle-by- cycle current limiting, as well as thermal shutdown for full protection under fault conditions. Anexternal shutdown connection selects operating or standby modes. Standby current is less than 200A. Heat sinks are generally unnecessary due the regulator's high efficiency. Adequate heat transfer is usually provided by soldering all package pins to a printed circuit board. The LM2574 includes internal frequency compensation and an internal 52kHz fixed frequency oscillator guaranteed to +10% of the frequency. Circuits constructed around the LM2574 use a standard series of inductors which are available from several different manufacturers. Features * 3.3V, 5V, 12V, 15V, and Adjustable Output Versions Adjustable Version Output 1.23V to 37V +4% Max. over Line and Load Conditions. * Guaranteed 0.5A Output Current * Wide Input Voltage, up to 40V Thermal Shutdown and Current Limit Protection Requires only 4 external Components. Shutdown Capability (Standby Mode) Low Power Standby Mode < 200A Typical High Efficiency * 52kHz Fixed Frequency Internal Oscillator Uses Standard Inductors Applications Simple High-efficiency Step-down (Buck) Regulator Efficient Pre-Regulator for Linear Regulators * On-card Switching Regulators Positive to Negative Converter (Buck-Boost) Ordering Information Part Number Temp. Range Package LM2574BN 40C to +85C 8-pin Plastic DIP LM2574BWM 40C to +85C 14-pin Wide SOIC LM2574-3.3BN 40C to +85C 8-pin Plastic DIP LM2574-3.3BWM 40C to +85C 14-pin Wide SOIC Pin Configuration rit] ~~ s- SIGGND 2(] 7 OUTPUT ON/OFF 3] 6 PWRGND 4(] [15 Vin 8-pin DIP (N) V4 Fo 14 + + 2 P7413 FB 3 F 12 OUTPUT SIGGND 4 Faw - ON/OFF 5 (4 F310 Vin PWRGND 644 P49 * ~ 7 1 8 14-pin SOIC (WM) * NC: solder to printed circuit for maximum heat transfer LM2574-5.0BN 40C to +85C 8-pin Plastic DIP LM2574-5.0BWM 40C to +85C 14-pin Wide SOIC LM2574-12BN 40C to +85C 8-pin Plastic DIP LM2574-12BWM 40C to +85C 14-pin Wide SOIC . LM2574-15BN 40C to +85C 8-pin Plastic DIP LM2574-15BWM 40C to +85C 14-pin Wide SOIC Typical Application 40V MAX UNREGULATED DC IN Cy + rT n oO Vin LM2574 OUT] PWR SIG ON/ GND GND OFF il REGULATED 330pH OUTPUT O + t1pa05 = Sour | 220uF Figure 1. Fixed Output Regulator Circuit 4-19LM2574 Micrel Absolute Maximum Ratings Maximum Supply Voltage LM2574 OFF Pin input Voltage Output Voltage to Ground (Steady State)... Internally Limited deneeseeeeeetnetnees -65C to +150C Power Dissipation ..........0.cceesecceeeeeeees Storage Temperature Range Minimum ESD Rating C = 100pF, R = 1.5kQ Operating Ratings Temperature Range desneeeeesseaneets 45V LM2574 v0.3V SV EVin Supply Voltage beceneeeneeeeeeee -1V LM2574 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 = 100mA. Symbol | Parameter Condition | Min | Typ | Max | Units SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit Figure 2 Vout Feedback Voltage Vin = 129, toap = 0.1A, Voyt = 5V 1.217 | 1.230 | 1.243 Vv Vour Feedback Voltage 0.1A $ lLgap $ 0.5A, 7VS Viy $40V, Voyp = 5V | 1.193 | 1.230 | 1.267 | Vv {LM2574) 1.180 1.280 Vv nN Efficiency Vin = 12, tLoap = 0.1A, Vout =5V 78 % SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3) Test Circuit Figure 3 Vout Output Voltage Vin = 12Y, Ioap = 0-14, Voyz = 3.3V 3.234 3.3 3.366 Vv Vout Output Voltage 0.1A <I oap 0.5A, 4.75V < Vin < 40V, 3.168 3.3 3.432 Vv (LM2574-3.3) Vout = 3.3V 3.135 3.465 Vv n Efficiency Vin = 12V, ILgap = 0.1A 73 % SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit Figure 3 Vour Output Voitage Vin = 12V, tloap = 9.14, Voyr = 5V 4.900 5.0 5.100 Vv Vout Output Voltage 0.14 ILoan 0.5A, 7VS Vy S$ 40V, 4.800 | 5.0 | 5.200] Vv (LM2574-5.0) Vout = 5V 4.750 5.250 Vv n Efficiency Vin = 129, loan = 0-1A, Voy = 5V 78 % SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit Figure 3 Vout Output Voltage Vin = 259, li gap = 0.1A, Voyz = 12V 11.760] 12 | 12.240 Vv Vout Output Voitage 0.1A< loa 0.5A, 15V < Vin < 40V, 11.520] 12 | 12.480 Vv (LM2574-12) Vout = 12V 11.400 12.600 Vv n Efficiency Vin = 25V, ILoap = 0.1A 88 %o SYSTEM PARAMETERS, 15V REGULATORS (Note 3) Test Circuit Figure 3 Vout Output Voltage Vin = 30V, Ioap = 0.14, Vout = 15V 14.700 | 15 | 15.300 Vv Vout Output Voltage 0.14 lLoap $ 0.5A, 18V < Vy < 40V, 14.400] 15 | 15.600 Vv (LM2574-15) Vout = 15V 14,250 15.750 Vv n Efficiency Vin = 30Y, lLgap = 0.1A 88 % 4-20LM2574 Micrel Electrical Characteristics (continued) Symbol | Parameter | Condition Min | Typ | Max | Units DEVICE PARAMETERS, ADJUSTABLE REGULATOR lp Feedback Bias Current Vout = 5V 50 100 n& 500 nA DEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORS fy Oscillator Frequency Note 8 47 52 58 kHz 42 63 kHz Voat Saturation Voltage lout = 0.54, Note 4 0.8 1.2 Vv 1.4 Vv 0c Max Duty Cycle (ON) Note 5 93 98 % ley Current Limit Peak Current, toy < Sus, Note 4 0.7 1.0 1.6 A 0.65 1.8 I Output Leakage Current Vin Note 6, Output = OV 2 mA Note 6, Output = -1V 7.5 30 Ig Quiescent Current Note 6 5 10 mA \evpy Standby Quiescent Current ON/OFF Pin = 5V (OFF) 50 200 LA Bia Thermal Resistance N Package, Junction to Ambient, Note 7 85 C WM Package, Junction to Ambient, Note 7 100 C/W ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS Test Circuit Figures 2, 3 Vin ON/OFF Input Level Vour = OV 2.2 1.4 Vv 2.4 Vv Vit ON/OFF Input Level Vout = 15V or 5V 1.2 1.0 Vv 0.8 Vv Ny ON/OFF Logic Current ON/OFF = 5V (OFF) 4 30 LA Ne ON/OFF Logic Current ON/OFF = 0V (ON) 0.01 10 pA Note 1 Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate 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 extremes 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 LM2574 is used as shown in Figure 1 test circuit, system performance will be shown in system parameters section of Electrical Character- istics. Note 4 Output (pin 2) sourcing current. No diode, inductor, or capacitor connected to input. Note 5 Feedback (pin 4) removed from output and connected to OV. Note6 Feedback (pin 4) removed from output and connected to 12V to force the output transistor OFF. Note 7 Junction to ambient thermal resistance with approximately 1 square inches of PC board copper surrounding the leads. 4-21LM2574 Micrel Typical Performance Characteristics (circuit of Figure 1) OUTPUT CURRENT {A} SUPPLY CURRENT (mA) INPUT VOLTAGE (V) OUTPUT VOLTAGE CHANGE (mv) -75 -50 -25 0 25 50 75 100125150 Supply Current Ground Ty Vout = 5 o 10 20 30 40 50 60 INPUT VOLTAGE (V) Current Limit Vipy = 25 a 75 -50-25 0 25 50 75100125 150 JUNCTION TEMPERATURE ("C) Minimum Operating Voltage = 1.23V Loap = 100 mA JUNCTION TEMPERATURE (C) Normalized Output Voltage 100 1 VIN = 12V 75 LOAD = 100mA 50 Normalized to Ty = 25C. Your =5V 25 0 Lat -25 60 -75 -100 -75 -60-25 0 25 50 75 100125150 JUNCTION TEMPERATURE (C) SUPPLY CURRENT (mA) SATURATION VOLTAGE (V) NORMALIZED FEEDBACK VOLTAGE {mv) NORMALIZED FREQUENCY (%) Standby Quiescent Current Supply Current vs. Duty Cycle VoN/oFF = Loap = 100 mA from 7V to 40V. STANDBY QUIESCENT CURRENT (pA) 100 -50-25 0 25 50 75100 125150 JUNCTION TEMPERATURE ('C) 0 20 40 60 80 DUTY CYCLE (%) Switch Saturation Voltage Efficiency 100 o a Vout = EFFICIENCY (%) a m oOo om & ~ a Vout =3V. ox a 3 2 o 10 15 20 25 30 35 40 INPUT VOLTAGE (V) 0 0.1 02 #03 04 05 0.5 SWITCH CURRENT (A} Feedback Pin Current Line Regulation 14 42 | Normalized to 100 in = 10 ~ a = = 10 Vout =5V | 5 a [Loan = 10ma z 50 T,)=25 > 6 J o 25 . Gi ; 3 2 S25 9 & a -50 2 a 4 = -75 & -100 -75 -50 -25 0 25 50 75 100 125150 JUNCTION TEMPERATURE (C) Q 5 10 15 20 25 30 INPUT VOLTAGE (Vv) Oscillator Frequency Drepout Voltage FIND = Normalized at LOAD = lLoab= mA INPUT-OUTPUT DIFFERENTIAL {) 6 Vin = 12 9 75-50-25 O 25 50 75 100125150 JUNCTION TEMPERATURE (C) -75 -50-25 0 25 60 75 100125150 JUNCTION TEMPERATURE (C) 4-22LM2574 Micrel Typical Performance Characteristics (continued) Normalized Feedback Voltage Feedback Voltage* vs Duty Cycle* Vin =1 ILoap = 100 mA Loap = 100mA Normalized to T, = 25C Vin= Vin =7 NORMALIZED FEEDBACK VOLTAGE (mY) FEEDBACK VOLTAGE CHANGE (mV) 25 75 -50-25 0 25 50 75 100125150 0 20 40 6c ac 100 JUNCTION TEMPERATURE ('C} DUTY CYCLE (%) * Adjustable version only a D nT Qo ct | de Cy LM2574 330UH Gy Lt LM2574- 330uH (adjustable) : oa our 2341 33,12, 18 | | L PWR SIG ON 3.09k L PWR SIG ON/ GND GND OFF GND GND OFF Lt Cour 110006 == 35h e 1k 7 Figure 2. Adjustable Regulator Test Circuit Figure 3. Fixed Regulator Test Circuit 11DQ06 Load q Block Diagrams Vin FEED. BACK FIXED GAIN 3.tk ERROR AMP 12a BAND-GAP. REFERENCE 1.23 BAND-GAP. 52 kHz THERMAL REFERENCE | OSCILLATOR SHUTDOWN] Note: Pin numbers are for the TO-220 package Fixed Reguiator Adjustable Regulator 4-23