LM2574 Micrel LM2574 52kHz Simple 0.5A Buck Regulator 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 and 5V 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 200µA. 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. All support documentation can be found on Micrel’s web site at www.micrel.com. • 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 < 200µA 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 Junction Temp. Range Package LM2574BN –40°C to +85°C 8-pin Plastic DIP LM2574-3.3BN –40°C to +85°C 8-pin Plastic DIP LM2574-5.0BN –40°C to +85°C 8-pin Plastic DIP Typical Application 40V MAX UNREGULATED DC IN FB VIN CIN 22µF 330µH LM2574 PWR GND SIG GND OUT ON/ OFF 11DQ05 REGULATED OUTPUT 0.5A COUT 220µF Figure 1. Fixed Output Regulator Circuit Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com December 2003 1 M9999-122303 LM2574 Micrel Pin Configuration 8 NC FB 1 7 OUTPUT SIG GND 2 ON/OFF 3 6 NC PWR GND 4 5 VIN 8-Pin DIP (N) M9999-122303 2 December 2003 LM2574 Micrel Absolute Maximum Ratings(1) Operating Ratings(1) 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 (TS) ............ –65°C to +150°C Minimum ESD Rating C = 100pF, R = 1.5kΩ ............................................... 2kV FB Pin ....................................................................... 1kV Lead Temperature (soldering, 10 sec.) ..................... 260°C Supply Voltage LM2574 ..................................................................... 40V Temperature Range LM2574 ......................................... –40°C ≤ TJ ≤ +125°C Maximum Junction Temperature (TJ ............................... 150°C Electrical Characteristics(2) 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 = 100mA. Symbol Parameter Condition System Parameters, Adjustable Regulators(3), Min Typ Max Units 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 η Efficiency VIN = 12V, ILOAD = 0.1A, VOUT = 5V System Parameters, 3.3V Regulators(3), 78 % 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 η Efficiency VIN = 12V, ILOAD = 0.1A System Parameters, 5V Regulators(3), 73 % 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 η Efficiency VIN = 12V, ILOAD = 0.1A, VOUT = 5V 78 % Notes: 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 “Electrical Characteristics.” 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. 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 Charac- teristics.” December 2003 3 M9999-122303 LM2574 Micrel Electrical Characteristics 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 VSAT Saturation Voltage IOUT = 0.5A(4) DC Max Duty Cycle (ON) Note 5 ICL Current Limit Peak Current, tON ≤ IL Output Leakage Current VIN, Note 6, Output = 0V Note 6, Output = –1V 47 42 3µs(4) IQ Quiescent Current Note 6 ISTBY Standby Quiescent Current ON/OFF Pin = 5V (OFF) θJA Thermal Resistance N Package, Junction to 93 98 0.7 0.65 1.0 Ambient(7) % 1.6 1.8 A 2 30 mA 7.5 5 10 mA 50 200 µA 85 °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 µA ON/OFF = 0V (ON) 0.01 10 µA Notes: 4. Output (pin 2) sourcing current. No diode, inductor, or capacitor connected to input. 5. Feedback (pin 4) removed from output and connected to 0V. 6. Feedback (pin 4) removed from output and connected to 12V to force the output transistor OFF. 7. Junction-to-ambient thermal resistance with approximately 1 square inches of PC board copper surrounding the leads. Test Circuit FB VIN LM2574 (adjustable) OUT PWR SIG ON/ GND GND OFF 330µH 3.09k 11DQ06 Load CIN 22µF COUT 220µF 1k Figure 2. Adjustable Regulator Test Circuit FB VIN LM2574– 3.3, 5 PWR GND 330µH OUT SIG ON/ GND OFF 11DQ06 COUT 220µF Load CIN 22µF Figure 3. Fixed Regulator Test Circuit M9999-122303 4 December 2003 LM2574 Micrel Typical Characteristics (Circuit of Figure 1) Supply Current vs. Duty Cycle Supply Current 16 17.5 SUPPLY CURRENT (mA) SUPPLY CURRENT (mA) 20.0 Measured at Ground Pin TJ = 25˚C VOUT = 5V 18 14 12 10 8 ILOAD to 0.5A 15.0 12.5 10.0 ILOAD = 100 mA 7.5 5.0 6 4 VIN from 7V to 40V 2.5 0 10 20 30 40 50 STANDBY QUIESCENT CURRENT (µA) 20 Standby Quiescent Current 0 60 0 20 INPUT VOLTAGE (V) 40 60 80 1.5 Efficiency 100 -55˚C -40˚C 0.7 25˚C 0.1 2.5 2.0 VOUT = 1.23V ILOAD = 100 mA 8 6 50 25 0 -25 -50 -75 -100 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (˚C) December 2003 VOUT = 3V 0 0 -2 -4 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 25˚C +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) 5 35 40 100 -6 5 5 Feedback Pin Current 2 +8 0.5A INPUT VOLTAGE (V) 4 0 NORMALIZED FREQUENCY (%) OUTPUT VOLTAGE CHANGE (mV) VIN = 12V ILOAD = 100mA Normalized to TJ = 25˚C VOUT = 5V 0.5 Normalized to V IN = 10V VOUT = 5V ILOAD = 100mA TJ = 25 10 Normalized Output Voltage 75 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) 3.5 100 mA 80 60 0 NORMALIZED FEEDBACK VOLTAGE (mV) INPUT VOLTAGE (V) 4.0 85 65 0.3 JUNCTION TEMPERATURE (˚C) 5.0 4.5 0.5A 70 0.5 125˚C 150˚C 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 = 0.2Ω 1.0 0.5 ILOAD = 100 mA 0 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (˚C) M9999-122303 LM2574 Micrel Typical Performance Characteristics (continued) Feedback Voltage vs Duty Cycle* 20 25 20 15 10 5 VIN = 12V ILOAD = 100mA Normalized to TJ = 25˚C FEEDBACK VOLTAGE CHANGE (mV) NORMALIZED FEEDBACK VOLTAGE (mV) Normalized Feedback Voltage* 0 -5 -10 -15 -20 -25 -75 -50 -25 0 25 50 75 100 125 150 ILOAD = 100 mA 15 10 5 VIN = 40V 0 -5 VIN = 7V -10 -15 -20 0 JUNCTION TEMPERATURE (˚C) 20 40 60 80 100 DUTY CYCLE (%) * Adjustable version only M9999-122303 6 December 2003 LM2574 Micrel 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 December 2003 Adjustable Regulator 7 M9999-122303 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) 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 The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a proAØkt can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is at Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2003 Micrel, Incorporated. M9999-122303 8 December 2003