LM2574_05

LM2574 Micrel, Inc. LM2574 52kHz Simple 0.5A Buck Regulator General Description 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 cycleby-cycle 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. Features • 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) Typical Application 40V MAX UNREGULATED DC IN CIN 22µF VIN LM2574 PWR GND FB 330µH OUT SIG ON/ GND OFF REGULATED OUTPUT 0.5A COU T 220µF 11DQ05 Figure 1. Fixed Output Regulator Circuit Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com July 2005 1 M9999-072805 LM2574 Micrel, Inc. Ordering Information Part Number Standard LM2574BN LM2574-3.3BN LM2574-5.0BN Pb-Free LM2574YN LM2574-3.3YN LM2574-5.0YN Junction Temp. Range –40ºC to +85ºC –40ºC to +85ºC –40ºC to +85ºC Package 8-pin Plastic DIP 8-pin Plastic DIP 8-pin Plastic DIP Pin Configuration FB 1 SIG GND 2 ON/OFF 3 PWR GND 4 8-Pin DIP (N) 8 NC 7 OUTPUT 6 NC 5 VIN M9999-072805 2 July 2005 LM2574 Micrel, Inc. Absolute Maximum 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 Operating Ratings(1) Supply Voltage LM2574...................................................................... 40V Temperature Range LM2574...........................................–40°C ≤ TJ ≤ +125°C Maximum Junction Temperature (TJ.......................... 150°C Electrical Characteristics(2) Symbol VOUT VOUT η VOUT VOUT η VOUT VOUT η 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 Characteristics.” 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. Parameter Condition Min Typ Max Regulators(3), Test Circuit Figure 2 0.1A ≤ ILOAD ≤ 0.5A, 7V≤ VIN ≤ 40V, VOUT = 5V Test Circuit Figure 3 VIN = 12V, ILOAD = 0.1A, VOUT = 5V VIN = 12V, ILOAD = 0.1A, VOUT = 5V 1.217 1.193 1.180 1.230 1.230 78 3.234 3.168 3.135 3.3 3.3 73 4.900 4.800 4.750 5.0 5.0 78 5.100 5.200 5.250 3.366 3.432 3.465 1.243 1.267 1.280 Units V V V % V V V % V V V % System Parameters, Adjustable Feedback Voltage Feedback Voltage (LM2574) Efficiency System Parameters, 3.3V Regulators(3), Output Voltage Output Voltage (LM2574-3.3) Efficiency Output Voltage Output Voltage (LM2574-5.0) Efficiency 0.1A ≤ ILOAD ≤ 0.5A, 4.75V ≤ VIN ≤ 40V, VOUT = 3.3V VIN = 12V, ILOAD = 0.1A VIN = 12V, ILOAD = 0.1A, VOUT = 3.3V System Parameters, 5V Regulators(3), Test Circuit Figure 3 0.1A ≤ ILOAD ≤ 0.5A, 7V≤ VIN ≤ 40V, VOUT = 5V VIN = 12V, ILOAD = 0.1A, VOUT = 5V VIN = 12V, ILOAD = 0.1A, VOUT = 5V July 2005 3 M9999-072805 LM2574 Micrel, Inc. Parameter Feedback Bias Current Condition VOUT = 5V Min Typ 50 Max 100 500 58 63 1.2 1.4 1.6 1.8 2 30 10 200 Units nA nA kHz kHz V V % A mA mA µA °C/W V V 1.0 0.8 30 10 V V µA µA Electrical Characteristics Symbol IB Device Parameters, Adjustable Regulator Device Parameters, Fixed and Adjustable Regulators fo VSAT DC ICL IL IQ Oscillator Frequency Saturation Voltage Max Duty Cycle (ON) Current Limit Output Leakage Current Quiescent Current Standby Quiescent Current Thermal Resistance ON/OFF Input Level ON/OFF Input Level ON/OFF Logic Current ON/OFF Logic Current Note 8 IOUT = 0.5A(4) Note 5 Peak Current, tON ≤ 3µs(4) VIN, Note 6, Output = 0V Note 6, Output = –1V Note 6 ON/OFF Pin = 5V (OFF) N Package, Junction VOUT = 0V VOUT = 5V ON/OFF = 5V (OFF) ON/OFF = 0V (ON) to Ambient(7) 2.2 2.4 93 0.7 0.65 47 42 52 0.8 98 1.0 7.5 5 50 85 1.4 1.2 4 0.01 ISTBY θJA On/Off Control, Fixed and Adjustable Regulators Test Circuit Figures 2, 3 VIH VIL IIH IIL 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 VIN FB CIN 22µF LM2574 (adjustable) OUT PWR SI G ON/ GND GND OFF 330µH 11DQ06 COU T 220µF 3.09k 1k Figure 2. Adjustable Regulator Test Circuit FB CIN 22µF LM2574– 3.3, 5, 12 OUT P W R S I G ON/ GND GND O F F VIN 330µH 11DQ06 COU T 220µF Figure 3. Fixed Regulator Test Circuit M9999-072805 4 July 2005 LM2574 Micrel, Inc. Typical Characteristics (Circuit of Figure 1) Supply Current 20 Supply Current vs. Duty Cycle 20.0 17.5 15.0 12.5 10.0 7.5 Standby Quiescent Current 200 150 18 16 14 12 10 8 6 4 0 10 20 30 Measured at Ground Pin TJ = 25˚C VOUT = 5V VIN = 40V 100 I LO AD = 100 mA VON/OFF = 5V VIN = 12V I LO AD to 0.5A 5.0 2.5 50 VIN from 7V to 40V 0 20 40 60 80 100 40 50 60 0 0 -75 -50 -25 0 25 50 75 100 125150 JU N C TI O N TEM PER ATU R E ( ˚ C ) INPUT VOLTAGE ( V) D U TY C YC LE ( % ) Current Limit 1.5 Switch Saturation Voltage 1.1 100 Efficiency 95 VOUT = 12V V IN = 25V 0.9 1 90 0.5A 100 mA 100 mA -55˚C -40˚C 0.7 85 80 75 70 65 25˚C 0.5 0.5A VOUT = 3V 0.5 125˚C 150˚C 0.3 0 0 -75 -50 -25 0 25 50 75 100125 150 JU N C TI O N TEM PER ATU R E ( ˚ C ) 0.1 0.2 0.3 0.4 0.5 60 0 5 10 15 20 25 30 35 40 SW I TC H C U R R EN T ( A) INPUT VOLTAGE ( V) Minimum Operating Voltage 5.0 4.5 Line Regulation 14 12 Feedback Pin Current 100 4.0 3.5 3.0 2.5 2.0 1.5 1.0 VOUT = 1.23V I LO AD = 100 mA 10 8 6 4 2 0 -2 -4 -6 0 Normalized to VIN = 10V VOUT = 5V ILO AD = 100mA TJ = 25 75 50 25 0 -25 -50 -75 0.5 0 -75 -50 -25 0 25 50 75 100125150 J U N C TI O N TEM PER ATU R E ( ˚ C ) 5 10 15 20 25 INPUT VOLTAGE ( V) 30 -100 -75 -50 -25 0 25 50 75 100 125150 JU N C TI O N TEM PER ATU R E ( ˚ C ) 100 Normalized Output Voltage VIN = 12V I LO AD = 100mA Normalized to TJ = 25 ˚C VOUT = 5V Oscillator Frequency +8 75 +6 +4 +2 0 -2 -4 --6 Normalized at 25˚ C 2.0 Dropout Voltage I LO AD = 0.5A ∆VOUT = 5% R IND = 0.2Ω 50 1.5 25 0 1.0 VIN = 40V -25 -50 0.5 I LO AD = 100 mA -75 -100 -75 -50 -25 0 25 50 75 100125150 VIN = 12V -8 -75 -50 -25 0 25 50 75 100125150 J U N C TI O N TEM PER ATU R E ( ˚ C ) 0 -75 -50 -25 0 25 50 75 100125150 JU N C TI O N TEM PER ATU R E ( ˚ C ) JU N C TI O N TEM PER ATU R E ( ˚ C ) July 2005 5 M9999-072805 LM2574 Micrel, Inc. Typical Performance Characteristics (continued) 25 Normalized Feedback Voltage* VIN = 12V I LO AD = 100mA Normalized to TJ = 25˚ C 20 Feedback Voltage vs Duty Cycle* I LO AD = 100 mA 20 15 15 10 5 10 5 0 0 VIN = 40V -5 -10 -5 -15 -10 VIN = 7V -20 -25 -75 -50 -25 0 -15 25 50 75 100125150 -20 0 20 40 60 80 100 JU N C TI O N TEM PER ATU R E ( ˚ C ) D U TY C YC LE ( % ) * Adjustable version only M9999-072805 6 July 2005 LM2574 Micrel, Inc. Block Diagrams V IN F EED BACK 1 INTERNAL REGULATOR ON/OFF 5 ON/OFF V IN 1 FIXED GAIN E R R OR A M P INTERNAL REGULATOR ON/OFF 5 ON/OFF 4 3.1k FIXED GAIN E R R OR A M P 1.0k + - COM PARAT OR 1/2 AMP SW ITCH DRIVER F EED BACK 4 + - + - COM PARAT OR 1/2 AMP SW ITCH DRIVER 2 THERMAL SHUTDOWN CURRENT LIMIT + - OUTPUT 2 THERMAL SHUTDOWN CURRENT LIMIT OUTPUT 1.23V BAND-GAP REFERENCE 52 kHz OSCILLATOR RESET 3 GND 1.23V BAND-GAP REFERENCE 52 kHz OSCILLATOR RESET 3 GND Note: Pin numbers are for the TO-220 package Fixed Regulator Adjustable Regulator July 2005 7 M9999-072805 LM2574 Micrel, Inc. Package Information PIN 1 DIMENSIONS: INCH (MM) 0.380 (9.65) 0.370 (9.40) 0.135 (3.43) 0.125 (3.18) 0.255 (6.48) 0.245 (6.22) 0.300 (7.62) 0.013 (0.330) 0.010 (0.254) 0.018 (0.57) 0.100 (2.54) 0.130 (3.30) 0.0375 (0.952) 0.380 (9.65) 0.320 (8.13) 8-Pin DIP (N) MICREL INC. TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA This 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 product 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 a Purchaser's own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2003 Micrel, Inc. M9999-072805 8 July 2005