LM2574, LM2574HV www.ti.com SNVS104C – JUNE 1999 – REVISED APRIL 2013 LM2574/LM2574HV SIMPLE SWITCHER™ 0.5A Step-Down Voltage Regulator Check for Samples: LM2574, LM2574HV FEATURES DESCRIPTION • The LM2574 series of regulators are monolithic integrated circuits that provide all the active functions for a step-down (buck) switching regulator, capable of driving a 0.5A load with excellent line and load regulation. These devices are available in fixed output voltages of 3.3V, 5V, 12V, 15V, and an adjustable output version. 1 23 • • • • • • • • • 3.3V, 5V, 12V, 15V, and Adjustable Output Versions Adjustable Version Output Voltage Range, 1.23V to 37V (57V for HV version) ±4% Max Over Line and Load Conditions Specified 0.5A Output Current Wide Input Voltage Range, 40V, up to 60V for HV Version Requires Only 4 External Components 52 kHz Fixed Frequency Internal Oscillator TTL Shutdown Capability, Low Power Standby Mode High Efficiency Uses Readily Available Standard Inductors Thermal Shutdown and Current Limit Protection APPLICATIONS • • • • Simple High-Efficiency Step-Down (Buck) Regulator Efficient Pre-Regulator for Linear Regulators On-Card Switching Regulators Positive to Negative Converter (Buck-Boost) Requiring a minimum number of external components, these regulators are simple to use and include internal frequency compensation and a fixedfrequency oscillator. The LM2574 series offers a high-efficiency replacement for popular three-terminal linear regulators. Because of its high efficiency, the copper traces on the printed circuit board are normally the only heat sinking needed. A standard series of inductors optimized for use with the LM2574 are available from several different manufacturers. This feature greatly simplifies the design of switch-mode power supplies. Other features include a specified ±4% tolerance on output voltage within specified input voltages and output load conditions, and ±10% on the oscillator frequency. External shutdown is included, featuring 50 μA (typical) standby current. The output switch includes cycle-by-cycle current limiting, as well as thermal shutdown for full protection under fault conditions. Typical Application (Fixed Output Voltage Versions) Note: Pin numbers are for 8-pin PDIP package. Figure 1. 1 2 3 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. SIMPLE SWITCHER is a trademark of Texas Instruments. All other trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 1999–2013, Texas Instruments Incorporated LM2574, LM2574HV SNVS104C – JUNE 1999 – REVISED APRIL 2013 www.ti.com Connection Diagram * No internal connection, but should be soldered to PC board for best heat transfer. Figure 2. 8-Lead PDIP (Top View) See Package Number P0008E 2 Submit Documentation Feedback Figure 3. 14-Lead Wide (Top View) SOIC (NPA) See Package Number NPA0014A Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV LM2574, LM2574HV www.ti.com SNVS104C – JUNE 1999 – REVISED APRIL 2013 These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Absolute Maximum Ratings (1) (2) Maximum Supply Voltage LM2574 45V LM2574HV 63V −0.3V ≤ V ≤ +VIN ON /OFF Pin Input Voltage Output Voltage to Ground (Steady State) −1V Minimum ESD Rating (C = 100 pF, R = 1.5 kΩ) 2 kV −65°C to +150°C Storage Temperature Range Lead Temperature (Soldering, 10 seconds) 260°C Maximum Junction Temperature 150°C Power Dissipation (1) (2) Internally Limited Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but do not ensure specific performance limits. For ensured specifications and test conditions, see the LM2574-3.3, LM2574HV-3.3 Electrical Characteristics. If Military/Aerospace specified devices are required, please contact the TI Sales Office/ Distributors for availability and specifications. Operating Ratings −40°C ≤ TJ ≤ +125°C Temperature Range LM2574/LM2574HV Supply Voltage LM2574 40V LM2574HV 60V LM2574-3.3, LM2574HV-3.3 Electrical Characteristics Specifications with standard type face are for TJ = 25°C, and those with boldface type apply over full Operating Temperature Range. Symbol Parameter Conditions LM2574-3.3 LM2574HV-3.3 Typ SYSTEM PARAMETERS Test Circuit in Figure 23 and Figure 24, VOUT Output Voltage VIN = 12V, ILOAD = 100 mA 3.3 4.75V ≤ VIN ≤ 40V, 0.1A ≤ ILOAD ≤ 0.5A VOUT Output Voltage LM2574HV 4.75V ≤ VIN ≤ 60V, 0.1A ≤ ILOAD ≤ 0.5A 3.3 η Efficiency VIN = 12V, ILOAD = 0.5A 72 (1) (2) (1) (2) Output Voltage LM2574 VOUT Limit Units (Limits) 3.234 3.366 V V(Min) V(Max) 3.168/3.135 3.432/3.465 V V(Min) V(Max) 3.168/3.135 3.450/3.482 V(Min) V(Max) 3.3 % All limits specified 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 specified via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level. 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 the Figure 24 test circuit, system performance will be as shown in system parameters section of Electrical Characteristics. Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV Submit Documentation Feedback 3 LM2574, LM2574HV SNVS104C – JUNE 1999 – REVISED APRIL 2013 www.ti.com LM2574-5.0, LM2574HV-5.0 Electrical Characteristics Specifications with standard type face are for TJ = 25°C, and those with boldface type apply over full Operating Temperature Range. Symbol Parameter Conditions LM2574-5.0 Units (Limits) LM2574HV-5.0 Typ SYSTEM PARAMETERS Test Circuit in Figure 23 and Figure 24, VOUT Output Voltage VIN = 12V, ILOAD = 100 mA 7V ≤ VIN ≤ 40V, 0.1A ≤ ILOAD ≤ 0.5A VOUT Output Voltage LM2574HV 7V ≤ VIN ≤ 60V, 0.1A ≤ ILOAD ≤ 0.5A 5 η Efficiency VIN = 12V, ILOAD = 0.5A 77 (1) (2) (1) 5 Output Voltage LM2574 VOUT Limit (2) 4.900 5.100 V V(Min) V(Max) 4.800/4.750 5.200/5.250 V V(Min) V(Max) 4.800/4.750 5.225/5.275 V(Min) V(Max) 5 % All limits specified 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 specified via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level. 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 the Figure 24 test circuit, system performance will be as shown in system parameters section of Electrical Characteristics. LM2574-12, LM2574HV-12 Electrical Characteristics Specifications with standard type face are for TJ = 25°C, and those with boldface type apply over full Operating Temperature Range. Symbol Parameter Conditions LM2574-12 LM2574HV-12 Typ SYSTEM PARAMETERS Test Circuit in Figure 23 and Figure 24, VOUT Output Voltage VIN = 25V, ILOAD = 100 mA 12 15V ≤ VIN ≤ 40V, 0.1A ≤ ILOAD ≤ 0.5A VOUT Output Voltage LM2574HV 15V ≤ VIN ≤ 60V, 0.1A ≤ ILOAD ≤ 0.5A 12 η Efficiency VIN = 15V, ILOAD = 0.5A 88 (1) (2) 4 (1) (2) Output Voltage LM2574 VOUT Limit Units (Limits) 11.76 12.24 V V(Min) V(Max) 11.52/11.40 12.48/12.60 V V(Min) V(Max) 11.52/11.40 12.54/12.66 V(Min) V(Max) 12 % All limits specified 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 specified via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level. 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 the Figure 24 test circuit, system performance will be as shown in system parameters section of Electrical Characteristics. Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV LM2574, LM2574HV www.ti.com SNVS104C – JUNE 1999 – REVISED APRIL 2013 LM2574-15, LM2574HV-15 Electrical Characteristics Specifications with standard type face are for TJ = 25°C, and those with boldface type apply over full Operating Temperature Range. Symbol Parameter Conditions LM2574-15 LM2574HV-15 Typ SYSTEM PARAMETERS Test Circuit in Figure 23 and Figure 24, VOUT Output Voltage VIN = 30V, ILOAD = 100 mA 15 18V ≤ VIN ≤ 40V, 0.1A ≤ ILOAD ≤ 0.5A VOUT Output Voltage LM2574HV 18V ≤ VIN ≤ 60V, 0.1A ≤ ILOAD ≤ 0.5A 15 η Efficiency VIN = 18V, ILOAD = 0.5A 88 (1) (2) (1) (2) Output Voltage LM2574 VOUT Limit Units (Limits) 14.70 15.30 V V(Min) V(Max) 14.40/14.25 15.60/15.75 V V(Min) V(Max) 14.40/14.25 15.68/15.83 V(Min) V(Max) 15 % All limits specified 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 specified via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level. 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 the Figure 24 test circuit, system performance will be as shown in system parameters section of Electrical Characteristics. LM2574-ADJ, LM2574HV-ADJ Electrical Characteristics Specifications with standard type face are for TJ = 25°C, and those with boldface type apply over full Operating Temperature Range. Unless otherwise specified, VIN = 12V, ILOAD = 100 mA. Symbol Parameter Conditions LM2574-ADJ LM2574HV-ADJ Typ SYSTEM PARAMETERS Test Circuit in Figure 23 and Figure 24 VFB VFB VFB η (1) (2) Feedback Voltage Limit Units (Limits) (1) (2) VIN = 12V, ILOAD = 100 mA 1.230 Feedback Voltage LM2574 7V ≤ VIN ≤ 40V, 0.1A ≤ ILOAD ≤ 0.5A VOUT Programmed for 5V. Circuit of Figure 24 1.230 Feedback Voltage LM2574HV 7V ≤ VIN ≤ 60V, 0.1A ≤ ILOAD ≤ 0.5A 1.230 Efficiency VIN = 12V, VOUT = 5V, ILOAD = 0.5A VOUT Programmed for 5V. Circuit of Figure 24 77 1.217 1.243 V V(Min) V(Max) 1.193/1.180 1.267/1.280 V V(Min) V(Max) 1.193/1.180 1.273/1.286 V(Min) V(Max) % All limits specified 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 specified via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level. 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 the Figure 24 test circuit, system performance will be as shown in system parameters section of Electrical Characteristics. Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV Submit Documentation Feedback 5 LM2574, LM2574HV SNVS104C – JUNE 1999 – REVISED APRIL 2013 www.ti.com All Output Voltage Versions Electrical Characteristics Specifications with standard type face are for TJ = 25°C, and those with boldface type apply over full Operating Temperature Range. Unless otherwise specified, VIN = 12V for the 3.3V, 5V, and Adjustable version, VIN = 25V for the 12V version, and VIN = 30V for the 15V version. ILOAD = 100 mA. Symbol Parameter Conditions LM2574-XX LM2574HV-XX Units (Limits) (1) Typ Limit 50 100/500 nA 47/42 58/63 kHz kHz(Min) kHz(Max) 1.2/1.4 V V(max) 93 % %(Min) 0.7/0.65 1.6/1.8 A A(Min) A(Max) DEVICE PARAMETERS Ib Feedback Bias Current Adjustable Version Only, VOUT = 5V fO Oscillator Frequency See VSAT DC Max Duty Cycle (ON) ICL Current Limit IL Current Output Leakage IQ Quiescent Current ISTBY θJA θJA θJA θJA Saturation Voltage (2) 52 IOUT = 0.5A See (3) (4) 98 Peak Current Output = 0V Output = −1V Output = −1V See 0.9 (3) (2) 1.0 2 30 mA(Max) mA mA(Max) 10 mA mA(Max) 200 μA μA(Max) 7.5 (5) (6) (5) 5 Standby Quiescent Current ON /OFF Pin= 5V (OFF) Thermal Resistance P Package, Junction to Ambient (7) P Package, Junction to Ambient (8) NPA Package, Junction to Ambient NPA Package, Junction to Ambient 50 92 72 10 2 78 (7) (8) °C/W ON /OFF CONTROL Test Circuit Figure 24 VIH VIL IH IIL (1) (2) (3) (4) (5) (6) (7) (8) 6 ON /OFF Pin Logic Input Level VOUT = 0V 1.4 2.2/2.4 V(Min) VOUT = Nominal Output Voltage 1.2 1.0/0.8 V(Max) ON /OFF Pin Input Current ON /OFF Pin = 5V (OFF) 12 30 μA μA(Max) 10 μA μA(Max) ON /OFF Pin = 0V (ON) 0 All limits specified 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 specified via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level. The oscillator frequency reduces to approximately 18 kHz in the event of an output short or an overload which causes the regulated output voltage to drop approximately 40% from the nominal output voltage. This self protection feature lowers the average power dissipation of the IC by lowering the minimum duty cycle from 5% down to approximately 2%.Figure 9 Output pin sourcing current. No diode, inductor or capacitor connected to output pin. Feedback pin removed from output and connected to 0V. Feedback pin removed from output and connected to +12V for the Adjustable, 3.3V, and 5V versions, and +25V for the 12V and 15V versions, to force the output transistor OFF. VIN = 40V (60V for high voltage version). Junction to ambient thermal resistance with approximately 1 square inch of printed circuit board copper surrounding the leads. Additional copper area will lower thermal resistance further. See Application Hints in this data sheet and the thermal model in Switchers Made Simple software. Junction to ambient thermal resistance with approximately 4 square inches of 1 oz. (0.0014 in. thick) printed circuit board copper surrounding the leads. Additional copper area will lower thermal resistance further (See Note 7) Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV LM2574, LM2574HV www.ti.com SNVS104C – JUNE 1999 – REVISED APRIL 2013 Typical Performance Characteristics (Circuit of Figure 24) Normalized Output Voltage Line Regulation Figure 4. Figure 5. Dropout Voltage Current Limit Figure 6. Figure 7. Supply Current Standby Quiescent Current Figure 8. Figure 9. Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV Submit Documentation Feedback 7 LM2574, LM2574HV SNVS104C – JUNE 1999 – REVISED APRIL 2013 www.ti.com Typical Performance Characteristics (continued) (Circuit of Figure 24) 8 Oscillator Frequency Switch Saturation Voltage Figure 10. Figure 11. Efficiency Minimum Operating Voltage Figure 12. Figure 13. Supply Current vs Duty Cycle Feedback Voltage vs Duty Cycle Figure 14. Figure 15. Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV LM2574, LM2574HV www.ti.com SNVS104C – JUNE 1999 – REVISED APRIL 2013 Typical Performance Characteristics (continued) (Circuit of Figure 24) Feedback Pin Current Junction to Ambient Thermal Resistance Figure 16. Figure 17. Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV Submit Documentation Feedback 9 LM2574, LM2574HV SNVS104C – JUNE 1999 – REVISED APRIL 2013 www.ti.com Typical Performance Characteristics (Circuit of Figure 24) Continuous Mode Switching Waveforms VOUT = 5V, 500 mA Load Current, L = 330 μH Notes: A: Output Pin Voltage, 10V/div B: Inductor Current, 0.2 A/div C: Output Ripple Voltage, 20 mV/div, AC-Coupled Horizontal Time Base: 5 μs/div Figure 18. Notes: A: Output Pin Voltage, 10V/div B: Inductor Current, 0.2 A/div C: Output Ripple Voltage, 20 mV/div, AC-Coupled Horizontal Time Base: 5 μs/div Figure 19. 500 mA Load Transient Response for Continuous Mode Operation. L = 330 μH, COUT = 300 μF Notes: A: Output Voltage, 50 mV/div. AC Coupled B: 100 mA to 500 mA Load Pulse Horizontal Time Base: 200 μs/div Figure 20. 10 Submit Documentation Feedback Discontinuous Mode Switching Waveforms VOUT = 5V, 100 mA Load Current, L = 100 μH 250 mA Load Transient Response for Discontinuous Mode Operation. L = 68 μH, COUT = 470 μF Notes: A: Output Voltage, 50 mV/div. AC Coupled B: 50 mA to 250 mA Load Pulse Horizontal Time Base: 200 μs/div Figure 21. Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV LM2574, LM2574HV www.ti.com SNVS104C – JUNE 1999 – REVISED APRIL 2013 Block Diagram R1 = 1k 3.3V, R2 = 1.7k 5V, R2 = 3.1k 12V, R2 = 8.84k 15V, R2 = 11.3k For Adj. Version R1 = Open, R2 = 0Ω Note: Pin numbers are for the 8-pin PDIP package. Figure 22. Test Circuit and Layout Guidelines CIN — 22 μF, 75V Aluminum Electrolytic COUT — 220 μF, 25V Aluminum Electrolytic D1 — Schottky, 11DQ06 L1 — 330 μH, 52627 (for 5V in, 3.3V out, use 100 μH, RL-1284-100) R1 — 2k, 0.1% R2 — 6.12k, 0.1% Figure 23. Fixed Output Voltage Versions Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV Submit Documentation Feedback 11 LM2574, LM2574HV SNVS104C – JUNE 1999 – REVISED APRIL 2013 www.ti.com Figure 24. Adjustable Output Voltage Version As in any switching regulator, layout is very important. Rapidly switching currents associated with wiring inductance generate voltage transients which can cause problems. For minimal inductance and ground loops, the length of the leads indicated by heavy lines should be kept as short as possible. Single-point grounding (as indicated) or ground plane construction should be used for best results. When using the Adjustable version, physically locate the programming resistors near the regulator, to keep the sensitive feedback wiring short. Table 1. Inductor Selection by Manufacturer's Part Number Inductor Value 68 μH 12 Pulse Eng. Renco NPI * RL-1284-68-43 NP5915 100 μH * RL-1284-100-43 NP5916 150 μH 52625 RL-1284-150-43 NP5917 220 μH 52626 RL-1284-220-43 NP5918/5919 330 μH 52627 RL-1284-330-43 NP5920/5921 470 μH 52628 RL-1284-470-43 NP5922 680 μH 52629 RL-1283-680-43 NP5923 1000 μH 52631 RL-1283-1000-43 * 1500 μH * RL-1283-1500-43 * 2200 μH * RL-1283-2200-43 * Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV LM2574, LM2574HV www.ti.com SNVS104C – JUNE 1999 – REVISED APRIL 2013 LM2574 Series Buck Regulator Design Procedure PROCEDURE (Fixed Output Voltage Versions) EXAMPLE (Fixed Output Voltage Versions) Given: VOUT = Regulated Output Voltage (3.3V, 5V, 12V, or 15V) VIN(Max) = Maximum Input Voltage ILOAD(Max) = Maximum Load Current Given: VOUT = 5V VIN(Max) = 15V ILOAD(Max) = 0.4A 1. Inductor Selection (L1) A. Select the correct Inductor value selection guide from Figure 25, Figure 26, Figure 27, or Figure 28. (Output voltages of 3.3V, 5V, 12V or 15V respectively). For other output voltages, see the design procedure for the adjustable version. B. From the inductor value selection guide, identify the inductance region intersected by VIN(Max) and ILOAD(Max). C. Select an appropriate inductor from Table 1. Part numbers are listed for three inductor manufacturers. The inductor chosen must be rated for operation at the LM2574 switching frequency (52 kHz) and for a current rating of 1.5 × ILOAD. For additional inductor information, see INDUCTOR SELECTION in Application Hints of this data sheet. 1. Inductor Selection (L1) A. Use the selection guide shown in Figure 26. B. From the selection guide, the inductance area intersected by the 15V line and 0.4A line is 330. C. Inductor value required is 330 μH. From Table 1, choose Pulse Engineering PE-52627, Renco RL-1284-330, or NPI NP5920/5921. 2. Output Capacitor Selection (COUT) 2. Output Capacitor Selection (COUT) A. The value of the output capacitor together with the inductor A. COUT = 100 μF to 470 μF standard aluminum electrolytic. defines the dominate pole-pair of the switching regulator loop. For B. Capacitor voltage rating = 20V. stable operation and an acceptable output ripple voltage, (approximately 1% of the output voltage) a value between 100 μF and 470 μF is recommended. B. The capacitor's voltage rating should be at least 1.5 times greater than the output voltage. For a 5V regulator, a rating of at least 8V is appropriate, and a 10V or 15V rating is recommended. Higher voltage electrolytic capacitors generally have lower ESR numbers, and for this reason it may be necessary to select a capacitor rated for a higher voltage than would normally be needed. 3. Catch Diode Selection (D1) A. The catch-diode current rating must be at least 1.5 times greater than the maximum load current. Also, if the power supply design must withstand a continuous output short, the diode should have a current rating equal to the maximum current limit of the LM2574. The most stressful condition for this diode is an overload or shorted output condition. B. The reverse voltage rating of the diode should be at least 1.25 times the maximum input voltage. 3. Catch Diode Selection (D1) A. For this example, a 1A current rating is adequate. B. Use a 20V 1N5817 or SR102 Schottky diode, or any of the suggested fast-recovery diodes shown in Table 2. 4. Input Capacitor (CIN) 4. Input Capacitor (CIN) An aluminum or tantalum electrolytic bypass capacitor located close A 22 μF aluminum electrolytic capacitor located near the input and to the regulator is needed for stable operation. ground pins provides sufficient bypassing. Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV Submit Documentation Feedback 13 LM2574, LM2574HV SNVS104C – JUNE 1999 – REVISED APRIL 2013 www.ti.com INDUCTOR VALUE SELECTION GUIDES (For Continuous Mode Operation) Figure 25. LM2574HV-3.3 Inductor Selection Guide Figure 26. LM2574HV-5.0 Inductor Selection Guide Figure 27. LM2574HV-12 Inductor Selection Guide Figure 28. LM2574HV-15 Inductor Selection Guide Figure 29. LM2574HV-ADJ Inductor Selection Guide 14 Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV LM2574, LM2574HV www.ti.com SNVS104C – JUNE 1999 – REVISED APRIL 2013 PROCEDURE (Adjustable Output Voltage Versions) Given: VOUT = Regulated Output Voltage VIN(Max) = Maximum Input Voltage ILOAD(Max) = Maximum Load Current F = Switching Frequency (Fixed at 52 kHz) EXAMPLE (Adjustable Output Voltage Versions) Given: VOUT = 24V VIN(Max) = 40V ILOAD(Max) = 0.4A F = 52 kHz 1. Programming Output Voltage (Selecting R1 and R2, as shown 1. Programming Output Voltage (Selecting R1 and R2) in Figure 24) Use the following formula to select the appropriate resistor values. R1 can be between 1k and 5k. (For best temperature coefficient and R2 = 1k (19.51−1) = 18.51k, closest 1% value is 18.7k stability with time, use 1% metal film resistors) 2. Inductor Selection (L1) A. Calculate the inductor Volt • microsecond constant, E • T (V • μs), from the following formula: B. Use the E • T value from the previous formula and match it with the E • T number on the vertical axis of the Inductor Value Selection Guide shown in Figure 29. C. On the horizontal axis, select the maximum load current. D. Identify the inductance region intersected by the E • T value and the maximum load current value, and note the inductor value for that region. E. Select an appropriate inductor from the table shown in Table 1. Part numbers are listed for three inductor manufacturers. The inductor chosen must be rated for operation at the LM2574 switching frequency (52 kHz) and for a current rating of 1.5 × ILOAD. For additional inductor information, see INDUCTOR SELECTION in Application Hints of this data sheet. 2. Inductor Selection (L1) A. Calculate E • T (V • μs) B. E • T = 185 V • μs C. ILOAD(Max) = 0.4A D. Inductance Region = 1000 E. Inductor Value = 1000 μH Choose from Pulse Engineering Part #PE-52631, or Renco Part #RL-1283-1000. 3. Output Capacitor Selection (COUT) 3. Output Capacitor Selection (COUT) A. The value of the output capacitor together with the inductor defines the dominate pole-pair of the switching regulator loop. For stable operation, the capacitor must satisfy the following However, for acceptable output ripple voltage select requirement: COUT ≥ 100 μF COUT = 100 μF electrolytic capacitor The above formula yields capacitor values between 5 μF and 1000 μF that will satisfy the loop requirements for stable operation. But to achieve an acceptable output ripple voltage, (approximately 1% of the output voltage) and transient response, the output capacitor may need to be several times larger than the above formula yields. B. The capacitor's voltage rating should be at last 1.5 times greater than the output voltage. For a 24V regulator, a rating of at least 35V is recommended. Higher voltage electrolytic capacitors generally have lower ESR numbers, and for this reasion it may be necessary to select a capacitor rate for a higher voltage than would normally be needed. Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV Submit Documentation Feedback 15 LM2574, LM2574HV SNVS104C – JUNE 1999 – REVISED APRIL 2013 www.ti.com PROCEDURE (Adjustable Output Voltage Versions) EXAMPLE (Adjustable Output Voltage Versions) 4. Catch Diode Selection (D1) A. The catch-diode current rating must be at least 1.5 times greater than the maximum load current. Also, if the power supply design must withstand a continuous output short, the diode should have a current rating equal to the maximum current limit of the LM2574. The most stressful condition for this diode is an overload or shorted output condition. Suitable diodes are shown in Table 2. B. The reverse voltage rating of the diode should be at least 1.25 times the maximum input voltage. 4. Catch Diode Selection (D1) A. For this example, a 1A current rating is adequate. B. Use a 50V MBR150 or 11DQ05 Schottky diode, or any of the suggested fast-recovery diodes in Table 2. 5. Input Capacitor (CIN) 5. Input Capacitor (CIN) An aluminum or tantalum electrolytic bypass capacitor located close A 22 μF aluminum electrolytic capacitor located near the input and to the regulator is needed for stable operation. ground pins provides sufficient bypassing. (See Table 2). To further simplify the buck regulator design procedure, TI is making available computer design software to be used with the Simple Switcher line of switching regulators. Switchers Made Simple (version 3.3) is available on a (3½″) diskette for IBM compatible computers from a TI sales office in your area. 16 Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV LM2574, LM2574HV www.ti.com SNVS104C – JUNE 1999 – REVISED APRIL 2013 Table 2. Diode Selection Guide VR 1 Amp Diodes Schottky 20V 1N5817 SR102 MBR120P 30V 1N5818 SR103 11DQ03 MBR130P 10JQ030 40V 1N5819 SR104 11DQ04 11JQ04 MBR140P 50V MBR150 SR105 11DQ05 11JQ05 60V MBR160 SR106 11DQ06 11JQ06 90V 11DQ09 Fast Recovery The following diodes are all rated to 100V 11DF1 10JF1 MUR110 HER102 APPLICATION HINTS INPUT CAPACITOR (CIN) To maintain stability, the regulator input pin must be bypassed with at least a 22 μF electrolytic capacitor. The capacitor's leads must be kept short, and located near the regulator. If the operating temperature range includes temperatures below −25°C, the input capacitor value may need to be larger. With most electrolytic capacitors, the capacitance value decreases and the ESR increases with lower temperatures and age. Paralleling a ceramic or solid tantalum capacitor will increase the regulator stability at cold temperatures. For maximum capacitor operating lifetime, the capacitor's RMS ripple current rating should be greater than (1) INDUCTOR SELECTION All switching regulators have two basic modes of operation: continuous and discontinuous. The difference between the two types relates to the inductor current, whether it is flowing continuously, or if it drops to zero for a period of time in the normal switching cycle. Each mode has distinctively different operating characteristics, which can affect the regulator performance and requirements. The LM2574 (or any of the Simple Switcher family) can be used for both continuous and discontinuous modes of operation. In many cases the preferred mode of operation is in the continuous mode. It offers better load regulation, lower peak switch, inductor and diode currents, and can have lower output ripple voltage. But it does require relatively large inductor values to keep the inductor current flowing continuously, especially at low output load currents. Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV Submit Documentation Feedback 17 LM2574, LM2574HV SNVS104C – JUNE 1999 – REVISED APRIL 2013 www.ti.com To simplify the inductor selection process, an inductor selection guide (nomograph) was designed (see Figure 25 through Figure 29). This guide assumes continuous mode operation, and selects an inductor that will allow a peak-to-peak inductor ripple current (ΔIIND) to be a certain percentage of the maximum design load current. In the LM2574 SIMPLE SWITCHER, the peak-to-peak inductor ripple current percentage (of load current) is allowed to change as different design load currents are selected. By allowing the percentage of inductor ripple current to increase for lower current applications, the inductor size and value can be kept relatively low. INDUCTOR RIPPLE CURRENT When the switcher is operating in the continuous mode, the inductor current waveform ranges from a triangular to a sawtooth type of waveform (depending on the input voltage). For a given input voltage and output voltage, the peak-to-peak amplitude of this inductor current waveform remains constant. As the load current rises or falls, the entire sawtooth current waveform also rises or falls. The average DC value of this waveform is equal to the DC load current (in the buck regulator configuration). If the load current drops to a low enough level, the bottom of the sawtooth current waveform will reach zero, and the switcher will change to a discontinuous mode of operation. This is a perfectly acceptable mode of operation. Any buck switching regulator (no matter how large the inductor value is) will be forced to run discontinuous if the load current is light enough. The curve shown in Figure 30 illustrates how the peak-to-peak inductor ripple current (ΔIIND) is allowed to change as different maximum load currents are selected, and also how it changes as the operating point varies from the upper border to the lower border within an inductance region (see INDUCTOR SELECTION). Figure 30. Inductor Ripple Current (ΔIIND) Range Based on Selection Guides from Figure 25 through Figure 29. Consider the following example: VOUT = 5V @ 0.4A VIN = 10V minimum up to 20V maximum The selection guide in Figure 26 shows that for a 0.4A load current, and an input voltage range between 10V and 20V, the inductance region selected by the guide is 330 μH. This value of inductance will allow a peak-to-peak inductor ripple current (ΔIIND) to flow that will be a percentage of the maximum load current. For this inductor value, the ΔIIND will also vary depending on the input voltage. As the input voltage increases to 20V, it approaches the upper border of the inductance region, and the inductor ripple current increases. Referring to the curve in Figure 30, it can be seen that at the 0.4A load current level, and operating near the upper border of the 330 μH inductance region, the ΔIIND will be 53% of 0.4A, or 212 mA p-p. This ΔIIND is important because from this number the peak inductor current rating can be determined, the minimum load current required before the circuit goes to discontinuous operation, and also, knowing the ESR of the output capacitor, the output ripple voltage can be calculated, or conversely, measuring the output ripple voltage and knowing the ΔIIND, the ESR can be calculated. 18 Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV LM2574, LM2574HV www.ti.com SNVS104C – JUNE 1999 – REVISED APRIL 2013 From the previous example, the Peak-to-peak Inductor Ripple Current (ΔIIND) = 212 mA p-p. Once the ΔIND value is known, the following three formulas can be used to calculate additional information about the switching regulator circuit: 1. Peak Inductor or peak switch current (2) 2. Minimum load current before the circuit becomes discontinuous (3) 3. Output Ripple Voltage = (ΔIIND) × (ESR of COUT) The selection guide chooses inductor values suitable for continuous mode operation, but if the inductor value chosen is prohibitively high, the designer should investigate the possibility of discontinuous operation. The computer design software Switchers Made Simple will provide all component values for discontinuous (as well as continuous) mode of operation. Inductors are available in different styles such as pot core, toroid, E-frame, bobbin core, etc., as well as different core materials, such as ferrites and powdered iron. The least expensive, the bobbin core type, consists of wire wrapped on a ferrite rod core. This type of construction makes for an inexpensive inductor, but since the magnetic flux is not completely contained within the core, it generates more electro-magnetic interference (EMI). This EMl can cause problems in sensitive circuits, or can give incorrect scope readings because of induced voltages in the scope probe. The inductors listed in the selection chart include powdered iron toroid for Pulse Engineering, and ferrite bobbin core for Renco. An inductor should not be operated beyond its maximum rated current because it may saturate. When an inductor begins to saturate, the inductance decreases rapidly and the inductor begins to look mainly resistive (the DC resistance of the winding). This can cause the inductor current to rise very rapidly and will affect the energy storage capabilities of the inductor and could cause inductor overheating. Different inductor types have different saturation characteristics, and this should be kept in mind when selecting an inductor. The inductor manufacturers' data sheets include current and energy limits to avoid inductor saturation. OUTPUT CAPACITOR An output capacitor is required to filter the output voltage and is needed for loop stability. The capacitor should be located near the LM2574 using short pc board traces. Standard aluminum electrolytics are usually adequate, but low ESR types are recommended for low output ripple voltage and good stability. The ESR of a capacitor depends on many factors, some which are: the value, the voltage rating, physical size and the type of construction. In general, low value or low voltage (less than 12V) electrolytic capacitors usually have higher ESR numbers. The amount of output ripple voltage is primarily a function of the ESR (Equivalent Series Resistance) of the output capacitor and the amplitude of the inductor ripple current (ΔIIND). See INDUCTOR RIPPLE CURRENT (ΔIIND) in Application Hints. The lower capacitor values (100 μF- 330 μF) will allow typically 50 mV to 150 mV of output ripple voltage, while larger-value capacitors will reduce the ripple to approximately 20 mV to 50 mV. Output Ripple Voltage = (ΔIIND) (ESR of COUT) To further reduce the output ripple voltage, several standard electrolytic capacitors may be paralleled, or a higher-grade capacitor may be used. Such capacitors are often called “high-frequency,” “low-inductance,” or “low-ESR.” These will reduce the output ripple to 10 mV or 20 mV. However, when operating in the continuous mode, reducing the ESR below 0.03Ω can cause instability in the regulator. Tantalum capacitors can have a very low ESR, and should be carefully evaluated if it is the only output capacitor. Because of their good low temperature characteristics, a tantalum can be used in parallel with aluminum electrolytics, with the tantalum making up 10% or 20% of the total capacitance. The capacitor's ripple current rating at 52 kHz should be at least 50% higher than the peak-to-peak inductor ripple current. Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV Submit Documentation Feedback 19 LM2574, LM2574HV SNVS104C – JUNE 1999 – REVISED APRIL 2013 www.ti.com CATCH DIODE Buck regulators require a diode to provide a return path for the inductor current when the switch is off. This diode should be located close to the LM2574 using short leads and short printed circuit traces. Because of their fast switching speed and low forward voltage drop, Schottky diodes provide the best efficiency, especially in low output voltage switching regulators (less than 5V). Fast-Recovery, High-Efficiency, or Ultra-Fast Recovery diodes are also suitable, but some types with an abrupt turn-off characteristic may cause instability and EMI problems. A fast-recovery diode with soft recovery characteristics is a better choice. Standard 60 Hz diodes (e.g., 1N4001 or 1N5400, etc.) are also not suitable. See Table 2 for Schottky and “soft” fast-recovery diode selection guide. OUTPUT VOLTAGE RIPPLE AND TRANSIENTS The output voltage of a switching power supply will contain a sawtooth ripple voltage at the switcher frequency, typically about 1% of the output voltage, and may also contain short voltage spikes at the peaks of the sawtooth waveform. The output ripple voltage is due mainly to the inductor sawtooth ripple current multiplied by the ESR of the output capacitor. (See INDUCTOR SELECTION in Application Hints.) The voltage spikes are present because of the fast switching action of the output switch, and the parasitic inductance of the output filter capacitor. To minimize these voltage spikes, special low inductance capacitors can be used, and their lead lengths must be kept short. Wiring inductance, stray capacitance, as well as the scope probe used to evaluate these transients, all contribute to the amplitude of these spikes. An additional small LC filter (20 μH & 100 μF) can be added to the output (as shown in Figure 36) to further reduce the amount of output ripple and transients. A 10 × reduction in output ripple voltage and transients is possible with this filter. FEEDBACK CONNECTION The LM2574 (fixed voltage versions) feedback pin must be wired to the output voltage point of the switching power supply. When using the adjustable version, physically locate both output voltage programming resistors near the LM2574 to avoid picking up unwanted noise. Avoid using resistors greater than 100 kΩ because of the increased chance of noise pickup. ON /OFF INPUT For normal operation, the ON /OFF pin should be grounded or driven with a low-level TTL voltage (typically below 1.6V). To put the regulator into standby mode, drive this pin with a high-level TTL or CMOS signal. The ON /OFF pin can be safely pulled up to +VIN without a resistor in series with it. The ON /OFF pin should not be left open. GROUNDING The 8-pin molded PDIP and the 14-pin SOIC package have separate power and signal ground pins. Both ground pins should be soldered directly to wide printed circuit board copper traces to assure low inductance connections and good thermal properties. THERMAL CONSIDERATIONS The 8-pin PDIP (P) package and the 14-pin SOIC (NPA) package are molded plastic packages with solid copper lead frames. The copper lead frame conducts the majority of the heat from the die, through the leads, to the printed circuit board copper, which acts as the heat sink. For best thermal performance, wide copper traces should be used, and all ground and unused pins should be soldered to generous amounts of printed circuit board copper, such as a ground plane. Large areas of copper provide the best transfer of heat (lower thermal resistance) to the surrounding air, and even double-sided or multilayer boards provide better heat paths to the surrounding air. Unless the power levels are small, using a socket for the 8-pin package is not recommended because of the additional thermal resistance it introduces, and the resultant higher junction temperature. 20 Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV LM2574, LM2574HV www.ti.com SNVS104C – JUNE 1999 – REVISED APRIL 2013 Because of the 0.5A current rating of the LM2574, the total package power dissipation for this switcher is quite low, ranging from approximately 0.1W up to 0.75W under varying conditions. In a carefully engineered printed circuit board, both the P and the NPA package can easily dissipate up to 0.75W, even at ambient temperatures of 60°C, and still keep the maximum junction temperature below 125°C. A curve, Figure 17, displaying thermal resistance vs. pc board area for the two packages is shown in Typical Performance Characteristics of this data sheet. These thermal resistance numbers are approximate, and there can be many factors that will affect the final thermal resistance. Some of these factors include board size, shape, thickness, position, location, and board temperature. Other factors are, the area of printed circuit copper, copper thickness, trace width, multi-layer, single- or double-sided, and the amount of solder on the board. The effectiveness of the pc board to dissipate heat also depends on the size, number and spacing of other components on the board. Furthermore, some of these components, such as the catch diode and inductor will generate some additional heat. Also, the thermal resistance decreases as the power level increases because of the increased air current activity at the higher power levels, and the lower surface to air resistance coefficient at higher temperatures. The data sheet thermal resistance curves and the thermal model in Switchers Made Simple software (version 3.3) can estimate the maximum junction temperature based on operating conditions. ln addition, the junction temperature can be estimated in actual circuit operation by using the following equation. Tj = Tcu + (θj-cu × PD) (4) With the switcher operating under worst case conditions and all other components on the board in the intended enclosure, measure the copper temperature (Tcu ) near the IC. This can be done by temporarily soldering a small thermocouple to the pc board copper near the IC, or by holding a small thermocouple on the pc board copper using thermal grease for good thermal conduction. The thermal resistance (θj-cu) for the two packages is: θj-cu = 42°C/W for the P-8 package θj-cu = 52°C/W for the NPA-14 package The power dissipation (PD) for the IC could be measured, or it can be estimated by using the formula: where • IS is obtained from the typical supply current curve (adjustable version use the supply current vs. duty cycle curve). (5) Additional Applications INVERTING REGULATOR Figure 31 shows a LM2574-12 in a buck-boost configuration to generate a negative 12V output from a positive input voltage. This circuit bootstraps the regulator's ground pin to the negative output voltage, then by grounding the feedback pin, the regulator senses the inverted output voltage and regulates it to −12V. Note: Pin numbers are for the 8-pin PDIP package. Figure 31. Inverting Buck-Boost Develops −12V Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV Submit Documentation Feedback 21 LM2574, LM2574HV SNVS104C – JUNE 1999 – REVISED APRIL 2013 www.ti.com For an input voltage of 8V or more, the maximum available output current in this configuration is approximately 100 mA. At lighter loads, the minimum input voltage required drops to approximately 4.7V. The switch currents in this buck-boost configuration are higher than in the standard buck-mode design, thus lowering the available output current. Also, the start-up input current of the buck-boost converter is higher than the standard buck-mode regulator, and this may overload an input power source with a current limit less than 0.6A. Using a delayed turn-on or an undervoltage lockout circuit (described in the next section) would allow the input voltage to rise to a high enough level before the switcher would be allowed to turn on. Because of the structural differences between the buck and the buck-boost regulator topologies, the LM2574 Series Buck Regulator Design Procedure can not be used to select the inductor or the output capacitor. The recommended range of inductor values for the buck-boost design is between 68 μH and 220 μH, and the output capacitor values must be larger than what is normally required for buck designs. Low input voltages or high output currents require a large value output capacitor (in the thousands of micro Farads). The peak inductor current, which is the same as the peak switch current, can be calculated from the following formula: where • • fosc = 52 kHz. Under normal continuous inductor current operating conditions, the minimum VIN represents the worst case. Select an inductor that is rated for the peak current anticipated. (6) Also, the maximum voltage appearing across the regulator is the absolute sum of the input and output voltage. For a −12V output, the maximum input voltage for the LM2574 is +28V, or +48V for the LM2574HV. The Switchers Made Simple version 3.3) design software can be used to determine the feasibility of regulator designs using different topologies, different input-output parameters, different components, etc. NEGATIVE BOOST REGULATOR Another variation on the buck-boost topology is the negative boost configuration. The circuit in Figure 32 accepts an input voltage ranging from −5V to −12V and provides a regulated −12V output. Input voltages greater than −12V will cause the output to rise above −12V, but will not damage the regulator. Note: Pin numbers are for 8-pin PDIP package. Figure 32. Negative Boost Because of the boosting function of this type of regulator, the switch current is relatively high, especially at low input voltages. Output load current limitations are a result of the maximum current rating of the switch. Also, boost regulators can not provide current limiting load protection in the event of a shorted load, so some other means (such as a fuse) may be necessary. 22 Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV LM2574, LM2574HV www.ti.com SNVS104C – JUNE 1999 – REVISED APRIL 2013 UNDERVOLTAGE LOCKOUT In some applications it is desirable to keep the regulator off until the input voltage reaches a certain threshold. An undervoltage lockout circuit which accomplishes this task is shown in Figure 33 while Figure 34 shows the same circuit applied to a buck-boost configuration. These circuits keep the regulator off until the input voltage reaches a predetermined level. VTH ≈ VZ1 + 2VBE (Q1) Note: Complete circuit not shown (see Figure 31). Note: Pin numbers are for 8-pin PDIP package. Figure 33. Undervoltage Lockout for Buck Circuit Note: Complete circuit not shown (see Figure 31 ). Note: Pin numbers are for 8-pin PDIP package. Figure 34. Undervoltage Lockout for Buck-Boost Circuit DELAYED STARTUP The ON /OFF pin can be used to provide a delayed startup feature as shown in Figure 35. With an input voltage of 20V and for the part values shown, the circuit provides approximately 10 ms of delay time before the circuit begins switching. Increasing the RC time constant can provide longer delay times. But excessively large RC time constants can cause problems with input voltages that are high in 60 Hz or 120 Hz ripple, by coupling the ripple into the ON /OFF pin. ADJUSTABLE OUTPUT, LOW-RIPPLE POWER SUPPLY A 500 mA power supply that features an adjustable output voltage is shown in Figure 36. An additional L-C filter that reduces the output ripple by a factor of 10 or more is included in this circuit. Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV Submit Documentation Feedback 23 LM2574, LM2574HV SNVS104C – JUNE 1999 – REVISED APRIL 2013 www.ti.com Note: Complete circuit not shown. Note: Pin numbers are for 8-pin PDIP package. Figure 35. Delayed Startup Note: Pin numbers are for 8-pin PDIP package. Figure 36. 1.2V to 55V Adjustable 500 mA Power Supply with Low Output Ripple Definition of Terms BUCK REGULATOR A switching regulator topology in which a higher voltage is converted to a lower voltage. Also known as a stepdown switching regulator. BUCK-BOOST REGULATOR A switching regulator topology in which a positive voltage is converted to a negative voltage without a transformer. DUTY CYCLE (D) Ratio of the output switch's on-time to the oscillator period. (7) CATCH DIODE OR CURRENT STEERING DIODE The diode which provides a return path for the load current when the LM2574 switch is OFF. EFFICIENCY (η) The proportion of input power actually delivered to the load. (8) 24 Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV LM2574, LM2574HV www.ti.com SNVS104C – JUNE 1999 – REVISED APRIL 2013 CAPACITOR EQUIVALENT SERIES RESISTANCE (ESR) The purely resistive component of a real capacitor's impedance (see Figure 37). It causes power loss resulting in capacitor heating, which directly affects the capacitor's operating lifetime. When used as a switching regulator output filter, higher ESR values result in higher output ripple voltages. Figure 37. Simple Model of a Real Capacitor Most standard aluminum electrolytic capacitors in the 100 μF–1000 μF range have 0.5Ω to 0.1Ω ESR. Highergrade capacitors (“low-ESR”, “high-frequency”, or “low-inductance”) in the 100 μF–1000 μF range generally have ESR of less than 0.15Ω. EQUIVALENT SERIES INDUCTANCE (ESL) The pure inductance component of a capacitor (see Figure 37). The amount of inductance is determined to a large extent on the capacitor's construction. In a buck regulator, this unwanted inductance causes voltage spikes to appear on the output. OUTPUT RIPPLE VOLTAGE The AC component of the switching regulator's output voltage. It is usually dominated by the output capacitor's ESR multiplied by the inductor's ripple current (ΔIIND). The peak-to-peak value of this sawtooth ripple current can be determined by readingINDUCTOR RIPPLE CURRENT (ΔIIND) of Application Hints. CAPACITOR RIPPLE CURRENT RMS value of the maximum allowable alternating current at which a capacitor can be operated continuously at a specified temperature. STANDBY QUIESCENT CURRENT (ISTBY) Supply current required by the LM2574 when in the standby mode (ON/OFF pin is driven to TTL-high voltage, thus turning the output switch OFF). INDUCTOR RIPPLE CURRENT (ΔIIND) The peak-to-peak value of the inductor current waveform, typically a sawtooth waveform when the regulator is operating in the continuous mode (vs. discontinuous mode). CONTINUOUS/DISCONTINUOUS MODE OPERATION Relates to the inductor current. In the continuous mode, the inductor current is always flowing and never drops to zero, vs. the discontinuous mode, where the inductor current drops to zero for a period of time in the normal switching cycle. INDUCTOR SATURATION The condition which exists when an inductor cannot hold any more magnetic flux. When an inductor saturates, the inductor appears less inductive and the resistive component dominates. Inductor current is then limited only by the DC resistance of the wire and the available source current. OPERATING VOLT MICROSECOND CONSTANT (E•Top) The product (in VoIt•μs) of the voltage applied to the inductor and the time the voltage is applied. This E•Top constant is a measure of the energy handling capability of an inductor and is dependent upon the type of core, the core area, the number of turns, and the duty cycle. Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV Submit Documentation Feedback 25 LM2574, LM2574HV SNVS104C – JUNE 1999 – REVISED APRIL 2013 www.ti.com REVISION HISTORY Changes from Revision B (April 2013) to Revision C • 26 Page Changed layout of National Data Sheet to TI format .......................................................................................................... 25 Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated Product Folder Links: LM2574 LM2574HV PACKAGE OPTION ADDENDUM www.ti.com 11-Apr-2013 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish (2) MSL Peak Temp Op Temp (°C) Top-Side Markings (3) (4) LM2574HVM-12 ACTIVE SOIC NPA 14 50 TBD Call TI Call TI -40 to 125 LM2574HVM -12 P+ LM2574HVM-12/NOPB ACTIVE SOIC NPA 14 50 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 LM2574HVM -12 P+ LM2574HVM-15 ACTIVE SOIC NPA 14 50 TBD Call TI Call TI -40 to 125 LM2574HVM -15 P+ LM2574HVM-15/NOPB ACTIVE SOIC NPA 14 50 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 LM2574HVM -15 P+ LM2574HVM-3.3 ACTIVE SOIC NPA 14 50 TBD Call TI Call TI -40 to 125 LM2574HVM -3.3 P+ LM2574HVM-3.3/NOPB ACTIVE SOIC NPA 14 50 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 LM2574HVM -3.3 P+ LM2574HVM-5.0 ACTIVE SOIC NPA 14 50 TBD Call TI Call TI -40 to 125 LM2574HVM -5.0 P+ LM2574HVM-5.0/NOPB ACTIVE SOIC NPA 14 50 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 LM2574HVM -5.0 P+ LM2574HVM-ADJ ACTIVE SOIC NPA 14 50 TBD Call TI Call TI -40 to 125 LM2574HVM -ADJ P+ LM2574HVM-ADJ/NOPB ACTIVE SOIC NPA 14 50 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 LM2574HVM -ADJ P+ LM2574HVMX-12/NOPB ACTIVE SOIC NPA 14 1000 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 LM2574HVM -12 P+ LM2574HVMX-15 ACTIVE SOIC NPA 14 1000 TBD Call TI Call TI -40 to 125 LM2574HVM -15 P+ LM2574HVMX-15/NOPB ACTIVE SOIC NPA 14 1000 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 LM2574HVM -15 P+ LM2574HVMX-3.3 ACTIVE SOIC NPA 14 1000 TBD Call TI Call TI -40 to 125 LM2574HVM -3.3 P+ LM2574HVMX-3.3/NOPB ACTIVE SOIC NPA 14 1000 Green (RoHS & no Sb/Br) CU SN Level-4-260C-72 HR -40 to 125 LM2574HVM -3.3 P+ LM2574HVMX-5.0 ACTIVE SOIC NPA 14 1000 TBD Call TI Call TI -40 to 125 LM2574HVM -5.0 P+ LM2574HVMX-5.0/NOPB ACTIVE SOIC NPA 14 1000 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 LM2574HVM -5.0 P+ Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 11-Apr-2013 Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish (2) MSL Peak Temp Op Temp (°C) Top-Side Markings (3) (4) LM2574HVMX-ADJ ACTIVE SOIC NPA 14 1000 TBD Call TI Call TI -40 to 125 LM2574HVM -ADJ P+ LM2574HVMX-ADJ/NOPB ACTIVE SOIC NPA 14 1000 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 LM2574HVM -ADJ P+ LM2574HVN-12 ACTIVE PDIP P 8 40 TBD Call TI Call TI -40 to 125 LM2574HVN -12 P+ LM2574HVN-12/NOPB ACTIVE PDIP P 8 40 Green (RoHS & no Sb/Br) Call TI Level-1-NA-UNLIM -40 to 125 LM2574HVN -12 P+ LM2574HVN-15 ACTIVE PDIP P 8 40 TBD Call TI Call TI -40 to 125 LM2574HVN -15 P+ LM2574HVN-15/NOPB ACTIVE PDIP P 8 40 Green (RoHS & no Sb/Br) Call TI Level-1-NA-UNLIM -40 to 125 LM2574HVN -15 P+ LM2574HVN-5.0 ACTIVE PDIP P 8 40 TBD Call TI Call TI -40 to 125 LM2574HVN -5.0 P+ LM2574HVN-5.0/NOPB ACTIVE PDIP P 8 40 Green (RoHS & no Sb/Br) Call TI Level-1-NA-UNLIM -40 to 125 LM2574HVN -5.0 P+ LM2574HVN-ADJ ACTIVE PDIP P 8 40 TBD Call TI Call TI -40 to 125 LM2574HVN -ADJ P+ LM2574HVN-ADJ/NOPB ACTIVE PDIP P 8 40 Green (RoHS & no Sb/Br) Call TI Level-1-NA-UNLIM -40 to 125 LM2574HVN -ADJ P+ LM2574M-12 ACTIVE SOIC NPA 14 50 TBD Call TI Call TI -40 to 125 LM2574M -12 P+ LM2574M-12/NOPB ACTIVE SOIC NPA 14 50 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 LM2574M -12 P+ LM2574M-3.3 ACTIVE SOIC NPA 14 50 TBD Call TI Call TI -40 to 125 LM2574M -3.3 P+ LM2574M-3.3/NOPB ACTIVE SOIC NPA 14 50 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 LM2574M -3.3 P+ LM2574M-5.0 ACTIVE SOIC NPA 14 50 TBD Call TI Call TI -40 to 125 LM2574M -5.0 P+ LM2574M-5.0/NOPB ACTIVE SOIC NPA 14 50 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 LM2574M -5.0 P+ LM2574M-ADJ ACTIVE SOIC NPA 14 50 TBD Call TI Call TI -40 to 125 LM2574M -ADJ P+ LM2574M-ADJ/NOPB ACTIVE SOIC NPA 14 50 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 LM2574M -ADJ P+ Addendum-Page 2 Samples PACKAGE OPTION ADDENDUM www.ti.com 11-Apr-2013 Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish (2) MSL Peak Temp Op Temp (°C) Top-Side Markings (3) (4) LM2574MX-12 ACTIVE SOIC NPA 14 1000 TBD Call TI Call TI -40 to 125 LM2574M -12 P+ LM2574MX-12/NOPB ACTIVE SOIC NPA 14 1000 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 LM2574M -12 P+ LM2574MX-3.3 ACTIVE SOIC NPA 14 1000 TBD Call TI Call TI -40 to 125 LM2574M -3.3 P+ LM2574MX-3.3/NOPB ACTIVE SOIC NPA 14 1000 Green (RoHS & no Sb/Br) CU SN Level-4-260C-72 HR -40 to 125 LM2574M -3.3 P+ LM2574MX-5.0 ACTIVE SOIC NPA 14 1000 TBD Call TI Call TI -40 to 125 LM2574M -5.0 P+ LM2574MX-5.0/NOPB ACTIVE SOIC NPA 14 1000 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 LM2574M -5.0 P+ LM2574MX-ADJ ACTIVE SOIC NPA 14 1000 TBD Call TI Call TI -40 to 125 LM2574M -ADJ P+ LM2574MX-ADJ/NOPB ACTIVE SOIC NPA 14 1000 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 LM2574M -ADJ P+ LM2574N-12 ACTIVE PDIP P 8 40 TBD Call TI Call TI -40 to 125 LM2574N -12 P+ LM2574N-12/NOPB ACTIVE PDIP P 8 40 Green (RoHS & no Sb/Br) Call TI Level-1-NA-UNLIM -40 to 125 LM2574N -12 P+ LM2574N-3.3 ACTIVE PDIP P 8 40 TBD Call TI Call TI -40 to 125 LM2574N -3.3 P+ LM2574N-3.3/NOPB ACTIVE PDIP P 8 40 Green (RoHS & no Sb/Br) Call TI Level-1-NA-UNLIM -40 to 125 LM2574N -3.3 P+ LM2574N-5.0 ACTIVE PDIP P 8 40 TBD Call TI Call TI -40 to 125 LM2574N -5.0 P+ LM2574N-5.0/NOPB ACTIVE PDIP P 8 40 Green (RoHS & no Sb/Br) Call TI Level-1-NA-UNLIM -40 to 125 LM2574N -5.0 P+ LM2574N-ADJ ACTIVE PDIP P 8 40 TBD Call TI Call TI -40 to 125 LM2574N -ADJ P+ LM2574N-ADJ/NOPB ACTIVE PDIP P 8 40 Green (RoHS & no Sb/Br) Call TI Level-1-NA-UNLIM -40 to 125 LM2574N -ADJ P+ (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. Addendum-Page 3 Samples PACKAGE OPTION ADDENDUM www.ti.com 11-Apr-2013 PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) Multiple Top-Side Markings will be inside parentheses. Only one Top-Side Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Top-Side Marking for that device. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 4 PACKAGE MATERIALS INFORMATION www.ti.com 8-Apr-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LM2574HVMX-12/NOPB SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 LM2574HVMX-15 SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 LM2574HVMX-15/NOPB SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 LM2574HVMX-3.3 SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 LM2574HVMX-3.3/NOPB SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 LM2574HVMX-5.0 SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 LM2574HVMX-5.0/NOPB SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 LM2574HVMX-ADJ SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 LM2574HVMX-ADJ/NOPB SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 LM2574MX-12 SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 LM2574MX-12/NOPB SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 LM2574MX-3.3 SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 LM2574MX-3.3/NOPB SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 LM2574MX-5.0 SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 LM2574MX-5.0/NOPB SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 LM2574MX-ADJ SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 LM2574MX-ADJ/NOPB SOIC NPA 14 1000 330.0 16.4 10.9 9.5 3.2 12.0 16.0 Q1 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 8-Apr-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM2574HVMX-12/NOPB SOIC NPA 14 1000 367.0 367.0 38.0 LM2574HVMX-15 SOIC NPA 14 1000 367.0 367.0 38.0 LM2574HVMX-15/NOPB SOIC NPA 14 1000 367.0 367.0 38.0 LM2574HVMX-3.3 SOIC NPA 14 1000 367.0 367.0 38.0 LM2574HVMX-3.3/NOPB SOIC NPA 14 1000 367.0 367.0 38.0 LM2574HVMX-5.0 SOIC NPA 14 1000 367.0 367.0 38.0 LM2574HVMX-5.0/NOPB SOIC NPA 14 1000 367.0 367.0 38.0 LM2574HVMX-ADJ SOIC NPA 14 1000 367.0 367.0 38.0 LM2574HVMX-ADJ/NOPB SOIC NPA 14 1000 367.0 367.0 38.0 LM2574MX-12 SOIC NPA 14 1000 367.0 367.0 38.0 LM2574MX-12/NOPB SOIC NPA 14 1000 367.0 367.0 38.0 LM2574MX-3.3 SOIC NPA 14 1000 367.0 367.0 38.0 LM2574MX-3.3/NOPB SOIC NPA 14 1000 367.0 367.0 38.0 LM2574MX-5.0 SOIC NPA 14 1000 367.0 367.0 38.0 LM2574MX-5.0/NOPB SOIC NPA 14 1000 367.0 367.0 38.0 LM2574MX-ADJ SOIC NPA 14 1000 367.0 367.0 38.0 LM2574MX-ADJ/NOPB SOIC NPA 14 1000 367.0 367.0 38.0 Pack Materials-Page 2 MECHANICAL DATA NPA0014B www.ti.com IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. 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