LM2574 Micrel LM2574 52kHz Simple 0.5A Buck Regulator Final Information General Description Features The LM2574 family is a series of easy to use fixed and adjustable switching voltage regulators. The LM2574 contains 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, and 12V fixed output versions, or an adjustable version with an output voltage range of 1.23V to 37V. Output voltage is guaranteed to 4% for specified input and load conditions. The LM2574 can supply 0.5A while maintaining excellent line and load regulation. The output switch includes cycle-bycycle current limiting, as well as thermal shutdown for full protection under fault conditions. An external 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. * 3.3V, 5V, 12V, 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 * * * * Ordering Information Part Number Pin Configuration FB 1 8 SIG GND 2 7 OUTPUT ON/OFF 3 6 * PWR GND 4 5 VIN Simple High-efficiency Step-down (Buck) Regulator Efficient Pre-Regulator for Linear Regulators On-card Switching Regulators Positive to Negative Converter (Buck-Boost) * 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 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 Typical Application 8-pin DIP (N) 40V MAX UNREGULATED DC IN FB VIN * * FB SIG GND ON/OFF PWR GND * 1 2 3 4 5 6 7 14 13 12 11 10 9 8 CIN 22F * * OUTPUT * VIN * * 330H LM2574 PWR GND SIG GND OUT ON/ OFF 11DQ05 REGULATED OUTPUT 0.5A COUT 220F 14-pin SOIC (WM) Figure 1. Fixed Output Regulator Circuit * NC: solder to printed circuit for maximum heat transfer Micrel, Inc. * 1849 Fortune Drive * San Jose, CA 95131 * USA * tel + 1 (408) 944-0800 * fax + 1 (408) 944-0970 * http://www.micrel.com August 1999 1 LM2574 LM2574 Micrel Absolute Maximum Ratings Operating Ratings Maximum Supply Voltage LM2574 ..................................................................... 45V OFF Pin Input Voltage ................................ -0.3V V VIN Output Voltage to Ground (Steady State) ..................... -1V Power Dissipation .................................... Internally Limited Storage Temperature Range ................... -65C to +150C Minimum ESD Rating C = 100pF, R = 1.5k ............................................... 2kV FB Pin ....................................................................... 1kV Lead Temperature (soldering, 10 sec.) ..................... 260C Maximum Junction Temperature ............................... 150C Temperature Range LM2574 ........................................... 40C TJ +125C Supply Voltage LM2574 ..................................................................... 40V Electrical Characteristics Specifications with standard typeface are for TJ = 25C, and those with boldface type apply over full Operating Temperature Range. Unless otherwise specified, Vin = 12V, and ILOAD = 100mA. Symbol Parameter Condition Min Typ Max Units SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit Figure 2 VOUT Feedback Voltage VIN = 12V, ILOAD = 0.1A, VOUT = 5V 1.217 1.230 1.243 V VOUT Feedback Voltage (LM2574) 0.1A ILOAD 0.5A, 7V VIN 40V, VOUT = 5V 1.193 1.180 1.230 1.267 1.280 V V Efficiency VIN = 12V, ILOAD = 0.1A, VOUT = 5V 78 % SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3) Test Circuit Figure 3 VOUT Output Voltage VIN = 12V, ILOAD = 0.1A, VOUT = 3.3V 3.234 3.3 3.366 V VOUT Output Voltage (LM2574-3.3) 0.1A ILOAD 0.5A, 4.75V VIN 40V, VOUT = 3.3V 3.168 3.135 3.3 3.432 3.465 V V Efficiency VIN = 12V, ILOAD = 0.1A 73 % SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit Figure 3 VOUT Output Voltage VIN = 12V, ILOAD = 0.1A, VOUT = 5V 4.900 5.0 5.100 V VOUT Output Voltage (LM2574-5.0) 0.1A ILOAD 0.5A, 7V VIN 40V, VOUT = 5V 4.800 4.750 5.0 5.200 5.250 V V Efficiency VIN = 12V, ILOAD = 0.1A, VOUT = 5V 78 % SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit Figure 3 VOUT Output Voltage VIN = 25V, ILOAD = 0.1A, VOUT = 12V 11.760 12 12.240 V VOUT Output Voltage (LM2574-12) 0.1A ILOAD 0.5A, 15V VIN 40V, VOUT = 12V 11.520 11.400 12 12.480 12.600 V V Efficiency VIN = 25V, ILOAD = 0.1A LM2574 2 88 % August 1999 LM2574 Micrel Electrical Characteristics (continued) Symbol Parameter Condition Min Typ Max Units 50 100 500 nA nA 52 58 63 kHz kHz 0.8 1.2 1.4 V V DEVICE PARAMETERS, ADJUSTABLE REGULATOR IB Feedback Bias Current VOUT = 5V DEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORS fo Oscillator Frequency Note 8 47 42 VSAT Saturation Voltage IOUT = 0.5A, Note 4 DC Max Duty Cycle (ON) Note 5 ICL Current Limit Peak Current, tON 3s, Note 4 IL Output Leakage Current VIN, Note 6, Output = 0V Note 6, Output = -1V 93 98 0.7 0.65 1.0 % 1.6 1.8 A 2 30 mA 7.5 IQ Quiescent Current Note 6 5 10 mA ISTBY Standby Quiescent Current ON/OFF Pin = 5V (OFF) 50 200 A JA Thermal Resistance N Package, Junction to Ambient, Note 7 WM Package, Junction to Ambient, Note 7 85 100 C/W C/W 1.4 V V ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS Test Circuit Figures 2, 3 VIH ON/OFF Input Level VOUT = 0V VIL ON/OFF Input Level VOUT = 5V IIH ON/OFF Logic Current IIL ON/OFF Logic Current 2.2 2.4 1.2 1.0 0.8 V V ON/OFF = 5V (OFF) 4 30 A ON/OFF = 0V (ON) 0.01 10 A 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 Characteristics. 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 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 with approximately 1 square inches of PC board copper surrounding the leads. August 1999 3 LM2574 LM2574 Micrel Typical Performance Characteristics Supply Current vs. Duty Cycle Supply Current 17.5 SUPPLY CURRENT (mA) SUPPLY CURRENT (mA) 20.0 Measured at Ground Pin TJ = 25C VOUT = 5V 16 14 12 10 8 ILOAD to 0.5A 15.0 12.5 10.0 ILOAD = 100 mA 7.5 5.0 VIN from 7V to 40V 2.5 6 4 0 10 20 30 40 50 Standby Quiescent Current STANDBY QUIESCENT CURRENT (A) 20 18 (Circuit of Figure 1) 0 60 0 20 INPUT VOLTAGE (V) 40 60 80 1.5 Efficiency 100 -55C -40C 0.7 25C 0.1 2.5 2.0 VOUT = 1.23V ILOAD = 100 mA 8 6 0 -2 -4 50 25 0 -25 -50 -75 -100 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (C) LM2574 10 15 20 10 15 20 25 30 75 50 25 0 -25 -50 -75 25 -100 -75 -50 -25 0 30 INPUT VOLTAGE (V) 25 50 75 100 125 150 JUNCTION TEMPERATURE (C) Oscillator Frequency Dropout Voltage 2.0 Normalized at 25C +6 +4 +2 0 -2 VIN = 40V -4 --6 VIN = 12V -8 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (C) 4 35 40 100 -6 5 5 Feedback Pin Current 2 0 NORMALIZED FREQUENCY (%) OUTPUT VOLTAGE CHANGE (mV) 75 VOUT = 3V INPUT VOLTAGE (V) 4 +8 0.5A 0 0.5 Normalized to V IN = 10V VOUT = 5V ILOAD = 100mA TJ = 25 10 Normalized Output Voltage VIN = 12V ILOAD = 100mA Normalized to TJ = 25C VOUT = 5V 0.4 Line Regulation 14 12 25 50 75 100 125 150 100 mA 75 SWITCH CURRENT (A) JUNCTION TEMPERATURE (C) 100 0.3 STANDBY QUIESCENT CURRENT (nA) 3.0 0.2 INPUT-OUTPUT DIFFERENTIAL (V) 3.5 80 60 0 NORMALIZED FEEDBACK VOLTAGE (mV) INPUT VOLTAGE (V) 4.0 100 mA 65 0.3 JUNCTION TEMPERATURE (C) 5.0 4.5 0.5A 85 70 0.5 125C 150C Minimum Operating Voltage VOUT = 12V 90 0.9 EFFICIENCY (%) SATURATION VOLTAGE (V) OUTPUT CURRENT (A) 95 0 -75 -50 -25 0 25 50 75 100 125 150 0.5 0 -75 -50 -25 0 VIN = 12V 50 JUNCTION TEMPERATURE (C) VI N = 25V 0.5 VON/OFF = 5V 100 0 -75 -50 -25 0 25 50 75 100 125 150 100 1.1 1.0 150 Switch Saturation Voltage 1 VIN = 40V DUTY CYCLE (%) Current Limit 1.5 200 1.5 ILOAD = 0.5A VOUT = 5% R IND = 0.2 1.0 0.5 ILOAD = 100 mA 0 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (C) August 1999 LM2574 Micrel Typical Performance Characteristics (continued) NORMALIZED FEEDBACK VOLTAGE (mV) Normalized Feedback Voltage* Feedback Voltage vs Duty Cycle* 20 25 15 10 5 FEEDBACK VOLTAGE CHANGE (mV) VIN = 12V ILOAD = 100mA Normalized to TJ = 25C 20 0 -5 -10 -15 -20 -25 -75 -50 -25 0 ILOAD = 100 mA 15 10 5 VIN = 40V 0 -5 VIN = 7V -10 -15 -20 25 50 75 100 125 150 0 20 JUNCTION TEMPERATURE (C) 40 60 80 100 DUTY CYCLE (%) * Adjustable version only FB FB VIN LM2574 (adjustable) OUT PWR SIG ON/ GND GND OFF LM2574- 3.3, 5, 12 CIN 22F 330H 11DQ06 COUT 220F 330H OUT SIG ON/ GND OFF PWR GND 3.09k Load CIN 22F 11DQ06 COUT 220F Load VIN 1k Figure 2. Adjustable Regulator Test Circuit Figure 3. Fixed Regulator Test Circuit Block Diagrams V IN 1 FEEDBACK 4 INTERNAL REGULATOR V IN INTERNAL REGULATOR 1 52 kHz OSCILLATOR FEEDBACK 1/2 AMP SWITCH COMPARATOR + - - ON/OFF 5 ON/OFF 2 OUTPUT 3 GND FIXED GAIN ERROR AMP + 1.23V BAND-GAP REFERENCE ON/OFF FIXED GAIN ERROR AMP 3.1k 1.0k 5 ON/OFF 4 - DRIVER RESET THERMAL SHUTDOWN CURRENT LIMIT 2 OUTPUT 3 GND 1.23V BAND-GAP REFERENCE 1/2 AMP SWITCH COMPARATOR + + - 52 kHz OSCILLATOR DRIVER RESET THERMAL SHUTDOWN CURRENT LIMIT Note: Pin numbers are for the TO-220 package Fixed Regulator August 1999 Adjustable Regulator 5 LM2574 LM2574 Micrel Package Information PIN 1 DIMENSIONS: INCH (MM) 0.380 (9.65) 0.370 (9.40) 0.255 (6.48) 0.245 (6.22) 0.135 (3.43) 0.125 (3.18) 0.300 (7.62) 0.013 (0.330) 0.010 (0.254) 0.018 (0.57) 0.130 (3.30) 0.100 (2.54) 0.380 (9.65) 0.320 (8.13) 0.0375 (0.952) 8-Pin DIP (N) PIN 1 DIMENSIONS: INCHES (MM) 0.292 (7.417) 0.286 (7.264) 0.029 (0.737) TYP 0.104 (2.642) 0.050 (1.270) 0.018 (0.457) 0.098 (2.489) TYP TYP 0.011 (0.279) 0.005 (0.127) 0.349 (8.865) 0.359 (9.119) 0.015 (0.381) x 45 0.297 (7.544) 0.291 (7.391) SEATING PLANE 5 TYP 5 5 TYP 0.338 (8.585) 0.318 (8.077) 0.416 (10.566) 0.396 (10.058) 14-Pin Wide SOP (WM) LM2574 6 August 1999 LM2574 August 1999 Micrel 7 LM2574 LM2574 Micrel MICREL INC. 1849 FORTUNE DRIVE TEL + 1 (408) 944-0800 FAX SAN JOSE, CA 95131 + 1 (408) 944-0970 WEB USA http://www.micrel.com This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc. (c) 1999 Micrel Incorporated LM2574 8 August 1999