LM2574

LM2574 Micrel 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 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. 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) Ordering Information Part Number LM2574BN LM2574-3.3BN LM2574-5.0BN Junction Temp. Range –40°C to +85°C –40°C to +85°C –40°C to +85°C Package 8-pin Plastic DIP 8-pin Plastic DIP 8-pin Plastic DIP Typical Application 40V MAX UNREGULATED DC IN VIN CIN 22µF PWR GND LM2574 SIG GND OUT ON/ OFF 11DQ05 330µH FB 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 FB 1 SIG GND 2 ON/OFF 3 PWR GND 4 8-Pin DIP (N) 8 NC 7 OUTPUT 6 NC 5 VIN M9999-122303 2 December 2003 LM2574 Micrel 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) 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 Regulators(3), Condition Test Circuit Figure 2 VIN = 12V, ILOAD = 0.1A, VOUT = 5V 0.1A ≤ ILOAD ≤ 0.5A, 7V≤ VIN ≤ 40V, VOUT = 5V VIN = 12V, ILOAD = 0.1A, VOUT = 5V Regulators(3), Test Circuit Figure 3 VIN = 12V, ILOAD = 0.1A, VOUT = 3.3V 0.1A ≤ ILOAD ≤ 0.5A, 4.75V ≤ VIN ≤ 40V, VOUT = 3.3V VIN = 12V, ILOAD = 0.1A Regulators(3), Test Circuit Figure 3 VIN = 12V, ILOAD = 0.1A, VOUT = 5V 0.1A ≤ ILOAD ≤ 0.5A, 7V≤ VIN ≤ 40V, VOUT = 5V VIN = 12V, ILOAD = 0.1A, VOUT = 5V 4.900 4.800 4.750 5.0 5.0 78 5.100 5.200 5.250 V V V % 3.234 3.168 3.135 3.3 3.3 73 3.366 3.432 3.465 V V V % 1.217 1.193 1.180 1.230 1.230 78 1.243 1.267 1.280 V V V % Min Typ Max Units System Parameters, Adjustable VOUT VOUT η Feedback Voltage Feedback Voltage (LM2574) Efficiency System Parameters, 3.3V VOUT VOUT η Output Voltage Output Voltage (LM2574-3.3) Efficiency System Parameters, 5V VOUT VOUT η Notes: Output Voltage Output Voltage (LM2574-5.0) Efficiency 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 Device Parameters, Adjustable Regulator IB Feedback Bias Current VOUT = 5V 50 100 500 nA nA Device Parameters, Fixed and Adjustable Regulators fo VSAT DC ICL IL IQ ISTBY θJA 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. Oscillator Frequency Saturation Voltage Max Duty Cycle (ON) Current Limit Output Leakage Current Quiescent Current Standby Quiescent Current Thermal Resistance Note 8 IOUT = 0.5A(4) Note 5 Peak Current, tON ≤ 3µs(4) 47 42 52 0.8 58 63 1.2 1.4 kHz kHz V V % 93 0.7 0.65 98 1.0 1.6 1.8 2 30 10 200 A mA mA µA °C/W VIN, Note 6, Output = 0V Note 6, Output = –1V Note 6 ON/OFF Pin = 5V (OFF) N Package, Junction to Ambient(7) 7.5 5 50 85 On/Off Control, Fixed and Adjustable Regulators Test Circuit Figures 2, 3 ON/OFF Input Level ON/OFF Input Level ON/OFF Logic Current ON/OFF Logic Current VOUT = 0V VOUT = 5V ON/OFF = 5V (OFF) ON/OFF = 0V (ON) 2.2 2.4 1.4 1.2 4 0.01 1.0 0.8 30 10 V V V V µA µA Test Circuit FB VIN CIN 22µF LM2574 (adjustable) OUT PWR SIG ON/ GND GND OFF 330µH 3.09k 11DQ06 COUT 220µF 1k Figure 2. Adjustable Regulator Test Circuit FB VIN CIN 22µF PWR GND LM2574– 3.3, 5 OUT SIG ON/ GND OFF 11DQ06 330µH COUT 220µF Figure 3. Fixed Regulator Test Circuit M9999-122303 4 Load Load December 2003 LM2574 Micrel Typical Characteristics (Circuit of Figure 1) Supply Current vs. Duty Cycle STANDBY QUIESCENT CURRENT (µA) Supply Current 20 18 SUPPLY CURRENT (mA) Standby Quiescent Current 200 VIN = 40V 16 14 12 10 8 6 4 0 10 20 30 SUPPLY CURRENT (mA) Measured at Ground Pin TJ = 25˚C VOUT = 5V 20.0 17.5 15.0 12.5 10.0 7.5 5.0 2.5 VIN from 7V to 40V 0 20 40 60 80 100 ILOAD = 100 mA 150 VON/OFF = 5V VIN = 12V 50 100 ILOAD to 0.5A 40 50 60 0 0 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (˚C) INPUT VOLTAGE (V) DUTY CYCLE (%) Current Limit 1.5 VI N = 25V SATURATION VOLTAGE (V) OUTPUT CURRENT (A) Switch Saturation Voltage 1.1 100 95 0.9 -55˚C -40˚C 0.7 25˚C EFFICIENCY (%) Efficiency VOUT = 12V 0.5A 100 mA 100 mA 0.5A VOUT = 3V 90 85 80 75 70 65 60 0 0.1 0.2 0.3 0.4 0.5 0 5 10 15 20 25 30 INPUT VOLTAGE (V) 1 0.5 0.5 125˚C 150˚C 0.3 SWITCH CURRENT (A) 0 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (˚C) 35 40 Minimum Operating Voltage NORMALIZED FEEDBACK VOLTAGE (mV) Line Regulation Normalized to V IN = 10V VOUT = 5V ILOAD = 100mA TJ = 25 STANDBY QUIESCENT CURRENT (nA) Feedback Pin Current 100 75 50 25 0 -25 -50 -75 -100 -75 -50 -25 0 25 50 75 100 125 150 5.0 4.5 4.0 INPUT VOLTAGE (V) 14 12 10 8 6 4 2 0 -2 -4 -6 0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -75 -50 -25 0 VOUT = 1.23V ILOAD = 100 mA 25 50 75 100 125 150 5 10 15 20 25 30 JUNCTION TEMPERATURE (˚C) INPUT VOLTAGE (V) JUNCTION TEMPERATURE (˚C) Normalized Output Voltage 100 OUTPUT VOLTAGE CHANGE (mV) Oscillator Frequency +8 +6 NORMALIZED FREQUENCY (%) Dropout Voltage 2.0 INPUT-OUTPUT DIFFERENTIAL (V) 75 50 25 0 -25 -50 -75 VIN = 12V ILOAD = 100mA Normalized to TJ = 25˚C VOUT = 5V Normalized at 25˚C 1.5 ILOAD = 0.5A ∆VOUT = 5% R IND = 0.2Ω +4 +2 0 -2 -4 --6 VIN = 40V 1.0 ILOAD = 100 mA 0.5 -100 -75 -50 -25 0 25 50 75 100 125 150 VIN = 12V -8 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (˚C) 0 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (˚C) JUNCTION TEMPERATURE (˚C) December 2003 5 M9999-122303 LM2574 Micrel Typical Performance Characteristics (continued) Normalized Feedback Voltage* NORMALIZED FEEDBACK VOLTAGE (mV) Feedback Voltage vs Duty Cycle* 20 FEEDBACK VOLTAGE CHANGE (mV) 25 20 15 10 5 0 -5 -10 -15 -20 -25 -75 -50 -25 0 VIN = 12V ILOAD = 100mA Normalized to TJ = 25˚C 15 10 5 0 -5 -10 -15 -20 0 20 40 ILOAD = 100 mA VIN = 40V VIN = 7V 25 50 75 100 125 150 60 80 100 JUNCTION TEMPERATURE (˚C) DUTY CYCLE (%) * Adjustable version only M9999-122303 6 December 2003 LM2574 Micrel Block Diagrams V IN FEEDBACK 1 4 3.1k INTERNAL REGULATOR ON/OFF 5 ON/OFF V IN 1 INTERNAL REGULATOR ON/OFF 5 ON/OFF FIXED GAIN ERROR AMP FIXED GAIN ERROR AMP COMPARATOR 1/2 AMP SWITCH FEEDBACK + 1.0k 4 + + - COMPARATOR 1/2 AMP SWITCH - + - DRIVER DRIVER 2 1.23V BAND-GAP REFERENCE OUTPUT 1.23V BAND-GAP REFERENCE 2 OUTPUT 52 kHz OSCILLATOR RESET THERMAL SHUTDOWN CURRENT LIMIT 3 GND 52 kHz OSCILLATOR RESET THERMAL SHUTDOWN CURRENT LIMIT 3 GND Note: Pin numbers are for the TO-220 package Fixed Regulator Adjustable Regulator December 2003 7 M9999-122303 LM2574 Micrel 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. 1849 FORTUNE DRIVE TEL SAN JOSE, CA 95131 WEB USA + 1 (408) 944-0800 FAX + 1 (408) 944-0970 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