LM2674 SIMPLE SWITCHER (R) Power Converter High Efficiency 500 mA Step-Down Voltage Regulator General Description The LM2674 series of regulators are monolithic integrated circuits built with a LMDMOS process. These regulators provide all the active functions for a step-down (buck) switching regulator, capable of driving a 500 mA load current with excellent line and load regulation. These devices are available in fixed output voltages of 3.3V, 5.0V, 12V, and an adjustable output version. Requiring a minimum number of external components, these regulators are simple to use and include patented internal frequency compensation (Patent Nos. 5,382,918 and 5,514,947) and a fixed frequency oscillator. The LM2674 series operates at a switching frequency of 260 kHz, thus allowing smaller sized filter components than what would be needed with lower frequency switching regulators. Because of its very high efficiency ( > 90%), the copper traces on the printed circuit board are the only heat sinking needed. A family of standard inductors for use with the LM2674 are available from several different manufacturers. This feature greatly simplifies the design of switch-mode power supplies using these advanced ICs. Also included in the datasheet are selector guides for diodes and capacitors designed to work in switch-mode power supplies. Other features include a guaranteed 1.5% tolerance on output voltage within specified input voltages and output load conditions, and 10% on the oscillator frequency. External shutdown is included, featuring typically 50 A stand-by current. The output switch includes current limiting, as well as thermal shutdown for full protection under fault conditions. To simplify the LM2674 buck regulator design procedure, there exists computer design software, LM267X Made Simple (version 6.0). Features n Efficiency up to 96% n Available in SO-8, 8-pin DIP and LLP packages n Computer Design Software LM267X Made Simple (version 6.0) n Simple and easy to design with n Requires only 5 external components n Uses readily available standard inductors n 3.3V, 5.0V, 12V, and adjustable output versions n Adjustable version output voltage range: 1.21V to 37V n 1.5% max output voltage tolerance over line and load conditions n Guaranteed 500mA output load current n 0.25 DMOS Output Switch n Wide input voltage range: 8V to 40V n 260 kHz fixed frequency internal oscillator n TTL shutdown capability, low power standby mode n Thermal shutdown and current limit protection Typical Applications n Simple High Efficiency ( > 90%) Step-Down (Buck) Regulator n Efficient Pre-Regulator for Linear Regulators n Positive-to-Negative Converter Typical Application 10004101 SIMPLE SWITCHER (R) is a registered trademark of National Semiconductor Corporation. Windows (R) is a registered trademark of Microsoft Corporation. (c) 2001 National Semiconductor Corporation DS100041 www.national.com LM2674 SIMPLE SWITCHER Power Converter High Efficiency 500 mA Step-Down Voltage Regulator May 2001 LM2674 Connection Diagrams 16-Lead LLP Surface Mount Package Top View 8-Lead Package Top View 10004102 SO-8/DIP Package See NSC Package Drawing Number MO8A/N08E 10004138 LLP Package See NSC Package Drawing Number LDA16A TABLE 1. Package Marking and Ordering Information Output Voltage Order Information Package Marking 12 LM2674LD-12 S0009B Supplied as: 16 Lead LLP 1000 Units on Tape and Reel 12 LM2674LDX-12 S0009B 4500 Units on Tape and Reel 3.3 LM2674LD-3.3 S000AB 1000 Units on Tape and Reel 3.3 LM2674LDX-3.3 S000AB 4500 Units on Tape and Reel 5.0 LM2674LD-5.0 S000BB 1000 Units on Tape and Reel 5.0 LM2674LDX-5.0 S000BB 4500 Units on Tape and Reel ADJ LM2674LD-ADJ S000CB 1000 Units on Tape and Reel ADJ LM2674LDX-ADJ S000CB 4500 Units on Tape and Reel 12 LM2674M-12 2674M-12 Shipped in Anti-Static Rails 12 LM2674MX-12 2674M-12 2500 Units on Tape and Reel SO-8 3.3 LM2674M-3.3 2674M-3.3 Shipped in Anti-Static Rails 3.3 LM2674MX-3.3 2674M-3.3 2500 Units on Tape and Reel 5.0 LM2674M-5.0 2674M-5.0 Shipped in Anti-Static Rails 2500 Units on Tape and Reel 5.0 LM2674MX-5.0 2674M-5.0 ADJ LM2674M-ADJ 2674M-ADJ Shipped in Anti-Static Rails ADJ LM2674MX-ADJ 2674M-ADJ 2500 Units on Tape and Reel DIP 12 LM2674N-12 LM2674N-12 Shipped in Anti-Static Rails 3.3 LM2674N-3.3 LM2674N-3.3 Shipped in Anti-Static Rails 5.0 LM2674N-5.0 LM2674N-5.0 Shipped in Anti-Static Rails ADJ LM2674N-ADJ LM2674N-ADJ Shipped in Anti-Static Rails www.national.com 2 (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage Lead Temperature 45V -0.1V VSH 6V ON/OFF Pin Voltage Switch Voltage to Ground M Package -1V Boost Pin Voltage VSW + 8V -0.3V VFB 14V Feedback Pin Voltage Vapor Phase (60s) +215C Infrared (15s) +220C N Package (Soldering, 10s) +260C LLP Package (See AN-1187) ESD Susceptibility Human Body Model (Note 2) Maximum Junction Temperature 2 kV Power Dissipation Internally Limited Storage Temperature Range -65C to +150C +150C Operating Ratings Supply Voltage 6.5V to 40V Junction Temperature Range -40C TJ +125C Electrical Characteristics LM2674-3.3 Specifications with standard type face are for TJ = 25C, and those with bold type face apply over full Operating Temperature Range. Symbol Parameter Conditions Typical Min Max (Note 4) (Note 5) (Note 5) Units SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3) VOUT Output Voltage VIN = 8V to 40V, ILOAD = 20 mA to 500 mA 3.3 3.251/3.201 3.350/3.399 V VOUT Output Voltage VIN = 6.5V to 40V, ILOAD = 20 mA to 250 mA 3.3 3.251/3.201 3.350/3.399 V Efficiency VIN = 12V, ILOAD = 500 mA 86 % LM2674-5.0 Symbol Parameter Conditions Typical Min Max (Note 4) (Note 5) (Note 5) Units SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3) VOUT Output Voltage VIN = 8V to 40V, ILOAD = 20 mA to 500 mA 5.0 4.925/4.850 5.075/5.150 VOUT Output Voltage VIN = 6.5V to 40V, ILOAD = 20 mA to 250 mA 5.0 4.925/4.850 5.075/5.150 Efficiency VIN = 12V, ILOAD = 500 mA 90 V V % LM2674-12 Symbol Parameter Conditions Typical Min Max (Note 4) (Note 5) (Note 5) 11.82/11.64 12.18/12.36 Units SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3) VOUT Output Voltage VIN = 15V to 40V, ILOAD = 20 mA to 500 mA 12 Efficiency VIN = 24V, ILOAD = 500 mA 94 V % LM2674-ADJ Symbol Parameter Conditions Typ Min Max (Note 4) (Note 5) (Note 5) 1.210 1.192/1.174 1.228/1.246 Units SYSTEM PARAMETERS Test Circuit Figure 3 (Note 3) VFB Feedback Voltage VIN = 8V to 40V, ILOAD = 20 mA to 500 mA VOUT Programmed for 5V (see Circuit of Figure 3) 3 V www.national.com LM2674 Absolute Maximum Ratings LM2674 LM2674-ADJ Symbol VFB (Continued) Parameter Conditions Feedback Voltage VIN = 6.5V to 40V, ILOAD = 20 mA to 250 mA VOUT Programmed for 5V (see Circuit of Figure 3) Efficiency VIN = 12V, ILOAD = 500 mA Typ Min Max (Note 4) (Note 5) (Note 5) 1.210 1.192/1.174 1.228/1.246 90 Units V % All Output Voltage Versions Specifications with standard type face are for TJ = 25C, and those with bold type face apply over full Operating Temperature Range. Unless otherwise specified, VIN = 12V for the 3.3V, 5V, and Adjustable versions and VIN = 24V for the 12V version, and ILOAD = 100 mA. Symbol Parameters Conditions Typ Min Max Units 3.6 mA DEVICE PARAMETERS IQ Quiescent Current VFEEDBACK = 8V 2.5 For 3.3V, 5.0V, and ADJ Versions VFEEDBACK = 15V 2.5 mA For 12V Versions ISTBY Standby Quiescent Current ICL Current Limit IL Output Leakage Current ON/OFF Pin = 0V 50 0.8 0.62/0.575 100/150 A 1.2/1.25 A VIN = 40V, ON/OFF Pin = 0V VSWITCH = 0V 1 25 A VSWITCH = -1V, ON/OFF Pin = 0V 6 15 mA 0.40/0.60 275 kHz RDS(ON) Switch On-Resistance ISWITCH = 500 mA 0.25 fO Oscillator Frequency Measured at Switch Pin 260 D Maximum Duty Cycle 95 % Minimum Duty Cycle 0 % 85 nA IBIAS Feedback Bias Current VS/D ON/OFF Pin Voltage Thesholds IS/D ON/OFF Pin Current JA Thermal Resistance VFEEDBACK = 1.3V ADJ Version Only ON/OFF Pin = 0V 225 1.4 0.8 2.0 V 20 7 37 A N Package, Junction to Ambient (Note 6) 95 M Package, Junction to Ambient (Note 6) 105 C/W Note 1: 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 device parameter specifications may not be guaranteed under these conditions. For guaranteed specifications and test conditions, see the Electrical Characteristics. Note 2: The human body model is a 100 pF capacitor discharged through a 1.5 k resistor into each pin. Note 3: External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator performance. When the LM2674 is used as shown in Figures 2, 3 test circuits, system performance will be as specified by the system parameters section of the Electrical Characteristics. Note 4: Typical numbers are at 25C and represent the most likely norm. Note 5: 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 correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). Note 6: 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 Information section in the application note accompanying this datasheet and the thermal model in LM267X Made Simple (version 6.0) software. The value J-A for the LLP (LD) package is specifically dependent on PCB trace area, trace material, and the number of layers and thermal vias. For improved thermal resistance and power dissipation for the LLP package, refer to Application Note AN-1187. www.national.com 4 LM2674 Typical Performance Characteristics Normalized Output Voltage Line Regulation 10004103 Drain-to-Source Resistance Efficiency Switch Current Limit Operating Quiescent Current 10004107 10004106 Standby Quiescent Current 10004105 10004104 ON/OFF Threshold Voltage 10004109 ON/OFF Pin Current (Sourcing) 10004110 5 10004108 10004111 www.national.com LM2674 Typical Performance Characteristics (Continued) Feedback Pin Bias Current Switching Frequency 10004113 10004112 Dropout Voltage -- 3.3V Option 10004114 Dropout Voltage -- 5.0V Option 10004115 www.national.com Peak Switch Current 10004116 6 LM2674 Block Diagram 10004117 * Active Inductor Patent Number 5,514,947 Active Capacitor Patent Number 5,382,918 FIGURE 1. 7 www.national.com LM2674 Typical Performance Characteristics (Circuit of Figure 2) Discontinuous Mode Switching Waveforms VIN = 20V, VOUT = 5V, ILOAD = 300 mA L = 15 H, COUT = 68 F (2x), COUTESR = 25 m Continuous Mode Switching Waveforms VIN = 20V, VOUT = 5V, ILOAD = 500 mA L = 100 H, COUT = 100 F, COUTESR = 0.1 10004118 10004119 Horizontal Time Base: 1 s/div Horizontal Time Base: 1 s/div A: VSW Pin Voltage, 10 V/div. B: Inductor Current, 0.2 A/div B: Inductor Current, 0.5 A/div A: VSW Pin Voltage, 10 V/div. C: Output Ripple Voltage, 50 mV/div AC-Coupled C: Output Ripple Voltage, 20 mV/div AC-Coupled Load Transient Response for Discontinuous Mode VIN = 20V, VOUT = 5V, L = 47 H, COUT = 68 F, COUTESR = 50 m Load Transient Response for Continuous Mode VIN = 20V, VOUT = 5V, L = 100 H, COUT = 100 F, COUTESR = 0.1 10004120 10004121 Horizontal Time Base: 50 s/div Horizontal Time Base: 200 s/div A: Output Voltage, 100 mV/div, AC-Coupled. A: Output Voltage, 100 mV/div, AC-Coupled. B: Load Current: 100 mA to 500 mA Load Pulse B: Load Current: 100 mA to 400 mA Load Pulse www.national.com 8 LM2674 Test Circuit and Layout Guidelines 10004122 CIN - 22 F, 50V Tantalum, Sprague "199D Series" COUT - 47 F, 25V Tantalum, Sprague "595D Series" D1 - 3.3A, 50V Schottky Rectifier, IR 30WQ05F L1 - 68 H Sumida #RCR110D-680L CB - 0.01 F, 50V Ceramic FIGURE 2. Standard Test Circuits and Layout Guides Fixed Output Voltage Versions 10004123 CIN - 22 F, 50V Tantalum, Sprague "199D Series" COUT - 47 F, 25V Tantalum, Sprague "595D Series" D1 - 3.3A, 50V Schottky Rectifier, IR 30WQ05F L1 - 68 H Sumida #RCR110D-680L R1 - 1.5 k, 1% CB - 0.01 F, 50V Ceramic For a 5V output, select R2 to be 4.75 k, 1% where VREF = 1.21V Use a 1% resistor for best stability. FIGURE 3. Standard Test Circuits and Layout Guides Adjustable Output Voltage Versions 9 www.national.com LM2674 LM2674 Series Buck Regulator Design Procedure (Fixed Output) PROCEDURE (Fixed Output Voltage Version) EXAMPLE (Fixed Output Voltage Version) To simplify the buck regulator design procedure, National Semiconductor is making available computer design software to be used with the SIMPLE SWITCHER line of switching regulators. LM267X Made Simple (version 6.0)is available on Windows (R) 3.1, NT, or 95 operating systems. Given: Given: VOUT = Regulated Output Voltage (3.3V, 5V, or 12V) VOUT = 5V VIN(max) = Maximum DC Input Voltage VIN(max) = 12V ILOAD(max) = Maximum Load Current ILOAD(max) = 500 mA 1. Inductor Selection (L1) 1. Inductor Selection (L1) A. Select the correct inductor value selection guide from Figure 4, Figure 5 or Figure 6 (output voltages of 3.3V, 5V, or 12V respectively). For all other voltages, see the design procedure for the adjustable version. A. Use the inductor selection guide for the 5V version shown in Figure 5. B. From the inductor value selection guide, identify the inductance region intersected by the Maximum Input Voltage line and the Maximum Load Current line. Each region is identified by an inductance value and an inductor code (LXX). B. From the inductor value selection guide shown in Figure 5, the inductance region intersected by the 12V horizontal line and the 500mA vertical line is 47 H, and the inductor code is L13. C. Select an appropriate inductor from the four manufacturer's part numbers listed in Figure 8. Each manufacturer makes a different style of inductor to allow flexibility in meeting various design requirements. Listed below are some of the differentiating characteristics of each manufacturer's inductors: C. The inductance value required is 47 H. From the table in Figure 8, go to the L13 line and choose an inductor part number from any of the four manufacturers shown. (In most instances, both through hole and surface mount inductors are available.) Schott: ferrite EP core inductors; these have very low leakage magnetic fields to reduce electro-magnetic interference (EMI) and are the lowest power loss inductors Renco: ferrite stick core inductors; benefits are typically lowest cost inductors and can withstand E * T and transient peak currents above rated value. Be aware that these inductors have an external magnetic field which may generate more EMI than other types of inductors. Pulse: powered iron toroid core inductors; these can also be low cost and can withstand larger than normal E * T and transient peak currents. Toroid inductors have low EMI. Coilcraft: ferrite drum core inductors; these are the smallest physical size inductors, available only as SMT components. Be aware that these inductors also generate EMI -- but less than stick inductors. Complete specifications for these inductors are available from the respective manufacturers. A table listing the manufacturers' phone numbers is located in Figure 9. 2. Output Capacitor Selection (COUT) 2. Output Capacitor Selection (COUT) A. Select an output capacitor from the output capacitor table in Figure 10. Using the output voltage and the inductance value found in the inductor selection guide, step 1, locate the appropriate capacitor value and voltage rating. A. Use the 5.0V section in the output capacitor table in Figure 10. Choose a capacitor value and voltage rating from the line that contains the inductance value of 47 H. The capacitance and voltage rating values corresponding to the 47 H inductor are the: www.national.com 10 PROCEDURE (Fixed Output Voltage Version) (Continued) EXAMPLE (Fixed Output Voltage Version) The capacitor list contains through-hole electrolytic capacitors from four different capacitor manufacturers and surface mount tantalum capacitors from two different capacitor manufacturers. It is recommended that both the manufacturers and the manufacturer's series that are listed in the table be used. A table listing the manufacturers' phone numbers is located in Figure 11. Surface Mount: 68 F/10V Sprague 594D Series. 100 F/10V AVX TPS Series. Through Hole: 68 F/10V Sanyo OS-CON SA Series. 150 F/35V Sanyo MV-GX Series. 150 F/35V Nichicon PL Series. 150 F/35V Panasonic HFQ Series. 3. Catch Diode Selection (D1) A. In normal operation, the average current of the catch diode is the load current times the catch diode duty cycle, 1-D (D is the switch duty cycle, which is approximately the output voltage divided by the input voltage). The largest value of the catch diode average current occurs at the maximum load current and maximum input voltage (minimum D). For normal operation, the catch diode current rating must be at least 1.3 times greater than its maximum average current. However, 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 LM2674. The most stressful condition for this diode is a shorted output condition. 3. Catch Diode Selection (D1) A. Refer to the table shown in Figure 12. In this example, a 1A, 20V Schottky diode will provide the best performance. If the circuit must withstand a continuous shorted output, a higher current Schottky diode is recommended. B. The reverse voltage rating of the diode should be at least 1.25 times the maximum input voltage. C. Because of their fast switching speed and low forward voltage drop, Schottky diodes provide the best performance and efficiency. This Schottky diode must be located close to the LM2674 using short leads and short printed circuit traces. 4. Input Capacitor (CIN) 4. Input Capacitor (CIN) 11 www.national.com LM2674 LM2674 Series Buck Regulator Design Procedure (Fixed Output) LM2674 LM2674 Series Buck Regulator Design Procedure (Fixed Output) (Continued) PROCEDURE (Fixed Output Voltage Version) EXAMPLE (Fixed Output Voltage Version) A low ESR aluminum or tantalum bypass capacitor is needed between the input pin and ground to prevent large voltage transients from appearing at the input. This capacitor should be located close to the IC using short leads. In addition, the RMS current rating of the input capacitor should be selected to be at least 12 the DC load current. The capacitor manufacturer data sheet must be checked to assure that this current rating is not exceeded. The curves shown in Figure 14 show typical RMS current ratings for several different aluminum electrolytic capacitor values. A parallel connection of two or more capacitors may be required to increase the total minimum RMS current rating to suit the application requirements. For an aluminum electrolytic capacitor, the voltage rating should be at least 1.25 times the maximum input voltage. Caution must be exercised if solid tantalum capacitors are used. The tantalum capacitor voltage rating should be twice the maximum input voltage. The tables in Figure 15 show the recommended application voltage for AVX TPS and Sprague 594D tantalum capacitors. It is also recommended that they be surge current tested by the manufacturer. The TPS series available from AVX, and the 593D and 594D series from Sprague are all surge current tested. Another approach to minimize the surge current stresses on the input capacitor is to add a small inductor in series with the input supply line. Use caution when using ceramic capacitors for input bypassing, because it may cause severe ringing at the VIN pin. The important parameters for the input capacitor are the input voltage rating and the RMS current rating. With a maximum input voltage of 12V, an aluminum electrolytic capacitor with a voltage rating greater than 15V (1.25 x VIN) would be needed. The next higher capacitor voltage rating is 16V. The RMS current rating requirement for the input capacitor in a buck regulator is approximately 12 the DC load current. In this example, with a 500mA load, a capacitor with an RMS current rating of at least 250 mA is needed. The curves shown in Figure 14 can be used to select an appropriate input capacitor. From the curves, locate the 16V line and note which capacitor values have RMS current ratings greater than 250 mA. For a through hole design, a 100 F/16V electrolytic capacitor (Panasonic HFQ series, Nichicon PL, Sanyo MV-GX series or equivalent) would be adequate. Other types or other manufacturers' capacitors can be used provided the RMS ripple current ratings are adequate. Additionally, for a complete surface mount design, electrolytic capacitors such as the Sanyo CV-C or CV-BS and the Nichicon WF or UR and the NIC Components NACZ series could be considered. For surface mount designs, solid tantalum capacitors can be used, but caution must be exercised with regard to the capacitor surge current rating and voltage rating. In this example, checking Figure 15, and the Sprague 594D series datasheet, a Sprague 594D 15 F, 25V capacitor is adequate. 5. Boost Capacitor (CB) 5. Boost Capacitor (CB) This capacitor develops the necessary voltage to turn the switch For this application, and all applications, use a 0.01 F, 50V gate on fully. All applications should use a 0.01 F, 50V ceramic ceramic capacitor. capacitor. www.national.com 12 LM2674 INDUCTOR VALUE SELECTION GUIDES (For Continuous Mode Operation) 10004128 10004126 FIGURE 6. LM2674-12 FIGURE 4. LM2674-3.3 10004129 10004127 FIGURE 7. LM2674-ADJ FIGURE 5. LM2674-5.0 13 www.national.com LM2674 INDUCTOR VALUE SELECTION GUIDES Ind. Inductance Current Ref. (H) (A) Desg. L2 150 L3 L4 Schott (For Continuous Mode Operation) (Continued) Renco Through Surface Through Hole Mount Hole Pulse Engineering Coilcraft Surface Through Surface Surface Mount Hole Mount Mount 0.21 67143920 67144290 RL-5470-4 RL1500-150 PE-53802 PE-53802-S DO1608-154 100 0.26 67143930 67144300 RL-5470-5 RL1500-100 PE-53803 PE-53803-S DO1608-104 68 0.32 67143940 67144310 RL-1284-68-43 RL1500-68 PE-53804 PE-53804-S DO1608-683 L5 47 0.37 67148310 67148420 RL-1284-47-43 RL1500-47 PE-53805 PE-53805-S DO1608-473 L6 33 0.44 67148320 67148430 RL-1284-33-43 RL1500-33 PE-53806 PE-53806-S DO1608-333 L7 22 0.52 67148330 67148440 RL-1284-22-43 RL1500-22 PE-53807 PE-53807-S DO1608-223 L9 220 0.32 67143960 67144330 RL-5470-3 RL1500-220 PE-53809 PE-53809-S DO3308-224 L10 150 0.39 67143970 67144340 RL-5470-4 RL1500-150 PE-53810 PE-53810-S DO3308-154 L11 100 0.48 67143980 67144350 RL-5470-5 RL1500-100 PE-53811 PE-53811-S DO3308-104 L12 68 0.58 67143990 67144360 RL-5470-6 RL1500-68 L13 47 0.70 67144000 67144380 RL-5470-7 RL1500-47 PE-53813 PE-53813-S DO3308-473 L14 33 0.83 67148340 67148450 RL-1284-33-43 RL1500-33 PE-53814 PE-53814-S DO3308-333 L15 22 0.99 67148350 67148460 RL-1284-22-43 RL1500-22 PE-53815 PE-53815-S DO3308-223 L18 220 0.55 67144040 67144420 RL-5471-2 RL1500-220 PE-53818 PE-53818-S DO3316-224 L19 150 0.66 67144050 67144430 RL-5471-3 RL1500-150 PE-53819 PE-53819-S DO3316-154 L20 100 0.82 67144060 67144440 RL-5471-4 RL1500-100 PE-53820 PE-53820-S DO3316-104 L21 68 0.99 67144070 67144450 RL-5471-5 RL1500-68 PE-53812 PE-53812-S DO3308-683 PE-53821 PE-53821-S DO3316-683 FIGURE 8. Inductor Manufacturers' Part Numbers Coilcraft Inc. Coilcraft Inc., Europe Phone (800) 322-2645 FAX (708) 639-1469 Phone +44 1236 730 595 FAX +44 1236 730 627 Phone (619) 674-8100 FAX (619) 674-8262 Pulse Engineering Inc., Phone +353 93 24 107 Europe FAX +353 93 24 459 Renco Electronics Inc. Phone (800) 645-5828 Pulse Engineering Inc. Schott Corp. FAX (516) 586-5562 Phone (612) 475-1173 FAX (612) 475-1786 FIGURE 9. Inductor Manufacturers' Phone Numbers www.national.com 14 (For Continuous Mode Operation) (Continued) Output Capacitor Output Voltage (V) 3.3 5.0 12 Inductance (H) Surface Mount Through Hole Sprague AVX TPS Sanyo OS-CON Sanyo MV-GX Nichicon Panasonic 594D Series Series SA Series Series PL Series HFQ Series (F/V) (F/V) (F/V) (F/V) (F/V) (F/V) 22 120/6.3 100/10 100/10 330/35 330/35 330/35 33 120/6.3 100/10 68/10 220/35 220/35 220/35 47 68/10 100/10 68/10 150/35 150/35 150/35 68 120/6.3 100/10 100/10 120/35 120/35 120/35 100 120/6.3 100/10 100/10 120/35 120/35 120/35 150 120/6.3 100/10 100/10 120/35 120/35 120/35 22 100/16 100/10 100/10 330/35 330/35 330/35 33 68/10 10010 68/10 220/35 220/35 220/35 47 68/10 100/10 68/10 150/35 150/35 150/35 68 100/16 100/10 100/10 120/35 120/35 120/35 100 100/16 100/10 100/10 120/35 120/35 120/35 150 100/16 100/10 100/10 120/35 120/35 120/35 22 120/20 (2x) 68/20 68/20 330/35 330/35 330/35 33 68/25 68/20 68/20 220/35 220/35 220/35 47 47/20 68/20 47/20 150/35 150/35 150/35 68 47/20 68/20 47/20 120/35 120/35 120/35 100 47/20 68/20 47/20 120/35 120/35 120/35 150 47/20 68/20 47/20 120/35 120/35 120/35 220 47/20 68/20 47/20 120/35 120/35 120/35 FIGURE 10. Output Capacitor Table Nichicon Corp. Panasonic AVX Corp. Sprague/Vishay Sanyo Corp. Phone (847) 843-7500 FAX (847) 843-2798 Phone (714) 373-7857 FAX (714) 373-7102 Phone (845) 448-9411 FAX (845) 448-1943 Phone (207) 324-4140 FAX (207) 324-7223 Phone (619) 661-6322 FAX (619) 661-1055 FIGURE 11. Capacitor Manufacturers' Phone Numbers 15 www.national.com LM2674 INDUCTOR VALUE SELECTION GUIDES LM2674 INDUCTOR VALUE SELECTION GUIDES 500mA Diodes VR Surface (For Continuous Mode Operation) (Continued) 3A Diodes Through Surface Through Mount Hole Mount Hole 20V SK12 1N5817 SK32 1N5820 B120 SR102 30V SK13 1N5818 SK33 1N5821 30WQ03F 31DQ03 SK34 1N5822 40V SR302 B130 11DQ03 MBRS130 SR103 SK14 1N5819 B140 11DQ04 30BQ040 MBR340 MBRS140 SR104 30WQ04F 31DQ04 10BQ040 MBRS340 SR304 10MQ040 MBRD340 15MQ040 50V SK15 MBR150 SK35 MBR350 B150 11DQ05 30WQ05F 31DQ05 10BQ050 SR105 SR305 FIGURE 12. Schottky Diode Selection Table International Rectifier Corp. Motorola, Inc. General Instruments Corp. Diodes, Inc. Phone (310) 322-3331 FAX (310) 322-3332 Phone (800) 521-6274 FAX (602) 244-6609 Phone (516) 847-3000 FAX (516) 847-3236 Phone (805) 446-4800 FAX (805) 446-4850 FIGURE 13. Diode Manufacturers' Phone Numbers 10004130 FIGURE 14. RMS Current Ratings for Low ESR Electrolytic Capacitors (Typical) www.national.com 16 (For Continuous Mode Operation) (Continued) AVX TPS Recommended Voltage Application Voltage Rating +85C Rating 3.3 6.3 5 10 10 20 12 25 15 35 Sprague 594D Recommended Voltage Application Voltage Rating +85C Rating 2.5 4 3.3 6.3 5 10 8 16 12 20 18 25 24 35 29 50 FIGURE 15. Recommended Application Voltage for AVX TPS and Sprague 594D Tantalum Chip Capacitors Derated for 85C. 17 www.national.com LM2674 INDUCTOR VALUE SELECTION GUIDES LM2674 LM2674 Series Buck Regulator Design Procedure (Adjustable Output) PROCEDURE (Adjustable Output Voltage Version) EXAMPLE (Adjustable Output Voltage Version) To simplify the buck regulator design procedure, National Semiconductor is making available computer design software to be used with the SIMPLE SWITCHER line of switching regulators. LM267X Made Simple (version 6.0) is available for use on Windows 3.1, NT, or 95 operating systems. Given: Given: VOUT = Regulated Output Voltage VOUT = 20V VIN(max) = Maximum Input Voltage VIN(max) = 28V ILOAD(max) = Maximum Load Current ILOAD(max) = 500 mA F = Switching Frequency (Fixed at a nominal 260 kHz). F = Switching Frequency (Fixed at a nominal 260 kHz). 1. Programming Output Voltage (Selecting R1 and R2, as shown in Figure 3) 1. Programming Output Voltage (Selecting R1 and R2, as shown in Figure 3) Use the following formula to select the appropriate resistor values. Select R1 to be 1 k, 1%. Solve for R2. where VREF = 1.21V Select a value for R1 between 240 and 1.5 k. The lower R2 = 1k (16.53 - 1) = 15.53 k, closest 1% value is 15.4 k. resistor values minimize noise pickup in the sensitive feedback R2 = 15.4 k. pin. (For the lowest temperature coefficient and the best stability with time, use 1% metal film resistors.) 2. Inductor Selection (L1) 2. Inductor Selection (L1) A. Calculate the inductor Volt * microsecond constant E * T (V * A. Calculate the inductor Volt * microsecond constant (E * T), s), from the following formula: where VSAT =internal switch saturation voltage=0.25V and VD = diode forward voltage drop = 0.5V 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 7. B. E * T = 21.6 (V * s) C. On the horizontal axis, select the maximum load current. C. ILOAD(max) = 500 mA D. Identify the inductance region intersected by the E * T value and the Maximum Load Current value. Each region is identified by an inductance value and an inductor code (LXX). D. From the inductor value selection guide shown in Figure 7, the inductance region intersected by the 21.6 (V * s) horizontal line and the 500mA vertical line is 100 H, and the inductor code is L20. E. Select an appropriate inductor from the four manufacturer's part numbers listed in Figure 8. For information on the different types of inductors, see the inductor selection in the fixed output voltage design procedure. E. From the table in Figure 8, locate line L20, and select an inductor part number from the list of manufacturers part numbers. 3. Output Capacitor Selection (COUT) 3. Output Capacitor SeIection (COUT) A. Select an output capacitor from the capacitor code selection guide in Figure 16. Using the inductance value found in the inductor selection guide, step 1, locate the appropriate capacitor code corresponding to the desired output voltage. A. Use the appropriate row of the capacitor code selection guide, in Figure 16. For this example, use the 15-20V row. The capacitor code corresponding to an inductance of 100 H is C20. www.national.com 18 (Continued) PROCEDURE (Adjustable Output Voltage Version) EXAMPLE (Adjustable Output Voltage Version) B. Select an appropriate capacitor value and voltage rating, using the capacitor code, from the output capacitor selection table in Figure 17. There are two solid tantalum (surface mount) capacitor manufacturers and four electrolytic (through hole) capacitor manufacturers to choose from. It is recommended that both the manufacturers and the manufacturer's series that are listed in the table be used. A table listing the manufacturers' phone numbers is located in Figure 11. B. From the output capacitor selection table in Figure 17, choose a capacitor value (and voltage rating) that intersects the capacitor code(s) selected in section A, C20. The capacitance and voltage rating values corresponding to the capacitor code C20 are the: Surface Mount: 33 F/25V Sprague 594D Series. 33 F/25V AVX TPS Series. Through Hole: 33 F/25V Sanyo OS-CON SC Series. 120 F/35V Sanyo MV-GX Series. 120 F/35V Nichicon PL Series. 120 F/35V Panasonic HFQ Series. Other manufacturers or other types of capacitors may also be used, provided the capacitor specifications (especially the 100 kHz ESR) closely match the characteristics of the capacitors listed in the output capacitor table. Refer to the capacitor manufacturers' data sheet for this information. 4. Catch Diode Selection (D1) A. In normal operation, the average current of the catch diode is the load current times the catch diode duty cycle, 1-D (D is the switch duty cycle, which is approximately VOUT/VIN). The largest value of the catch diode average current occurs at the maximum input voltage (minimum D). For normal operation, the catch diode current rating must be at least 1.3 times greater than its maximum average current. However, if the power supply design must withstand a continuous output short, the diode should have a current rating greater than the maximum current limit of the LM2674. The most stressful condition for this diode is a shorted output condition. 4. Catch Diode Selection (D1) A. Refer to the table shown in Figure 12. Schottky diodes provide the best performance, and in this example a 500mA, 40V Schottky diode would be a good choice. If the circuit must withstand a continuous shorted output, a higher current (at least 1.2A) Schottky diode is recommended. B. The reverse voltage rating of the diode should be at least 1.25 times the maximum input voltage. C. Because of their fast switching speed and low forward voltage drop, Schottky diodes provide the best performance and efficiency. The Schottky diode must be located close to the LM2674 using short leads and short printed circuit traces. 19 www.national.com LM2674 LM2674 Series Buck Regulator Design Procedure (Adjustable Output) LM2674 LM2674 Series Buck Regulator Design Procedure (Adjustable Output) (Continued) PROCEDURE (Adjustable Output Voltage Version) EXAMPLE (Adjustable Output Voltage Version) 5. Input Capacitor (CIN) A low ESR aluminum or tantalum bypass capacitor is needed between the input pin and ground to prevent large voltage transients from appearing at the input. This capacitor should be located close to the IC using short leads. In addition, the RMS current rating of the input capacitor should be selected to be at least 12 the DC load current. The capacitor manufacturer data sheet must be checked to assure that this current rating is not exceeded. The curves shown in Figure 14 show typical RMS current ratings for several different aluminum electrolytic capacitor values. A parallel connection of two or more capacitors may be required to increase the total minimum RMS current rating to suit the application requirements. For an aluminum electrolytic capacitor, the voltage rating should be at least 1.25 times the maximum input voltage. Caution must be exercised if solid tantalum capacitors are used. The tantalum capacitor voltage rating should be twice the maximum input voltage. The tables in Figure 15 show the recommended application voltage for AVX TPS and Sprague 594D tantalum capacitors. It is also recommended that they be surge current tested by the manufacturer. The TPS series available from AVX, and the 593D and 594D series from Sprague are all surge current tested. Another approach to minimize the surge current stresses on the input capacitor is to add a small inductor in series with the input supply line. Use caution when using ceramic capacitors for input bypassing, because it may cause severe ringing at the VIN pin. 5. Input Capacitor (CIN) The important parameters for the input capacitor are the input voltage rating and the RMS current rating. With a maximum input voltage of 28V, an aluminum electrolytic capacitor with a voltage rating of at least 35V (1.25 x VIN) would be needed. The RMS current rating requirement for the input capacitor in a buck regulator is approximately 12 the DC load current. In this example, with a 500mA load, a capacitor with an RMS current rating of at least 250 mA is needed. The curves shown in Figure 14 can be used to select an appropriate input capacitor. From the curves, locate the 35V line and note which capacitor values have RMS current ratings greater than 250 mA. For a through hole design, a 68 F/35V electrolytic capacitor (Panasonic HFQ series, Nichicon PL, Sanyo MV-GX series or equivalent) would be adequate. Other types or other manufacturers' capacitors can be used provided the RMS ripple current ratings are adequate. Additionally, for a complete surface mount design, electrolytic capacitors such as the Sanyo CV-C or CV-BS, and the Nichicon WF or UR and the NIC Components NACZ series could be considered. For surface mount designs, solid tantalum capacitors can be used, but caution must be exercised with regard to the capacitor surge current rating and voltage rating. In this example, checking Figure 15, and the Sprague 594D series datasheet, a Sprague 594D 15 F, 50V capacitor is adequate. 6. Boost Capacitor (CB) 6. Boost Capacitor (CB) This capacitor develops the necessary voltage to turn the switch For this application, and all applications, use a 0.01 F, 50V gate on fully. All applications should use a 0.01 F, 50V ceramic ceramic capacitor. capacitor. Inductance (H) Case Style (Note 7) Output Voltage (V) 22 33 47 68 100 150 220 SM and TH 1.21-2.50 -- -- -- -- C1 C2 C3 SM and TH 2.50-3.75 -- -- -- C1 C2 C3 C3 SM and TH 3.75-5.0 -- -- C4 C5 C6 C6 C6 SM and TH 5.0-6.25 -- C4 C7 C6 C6 C6 C6 SM and TH 6.25-7.5 C8 C4 C7 C6 C6 C6 C6 SM and TH 7.5-10.0 C9 C10 C11 C12 C13 C13 C13 SM and TH 10.0-12.5 C14 C11 C12 C12 C13 C13 C13 SM and TH 12.5-15.0 C15 C16 C17 C17 C17 C17 C17 SM and TH 15.0-20.0 C18 C19 C20 C20 C20 C20 C20 SM and TH 20.0-30.0 C21 C22 C22 C22 C22 C22 C22 TH 30.0-37.0 C23 C24 C24 C25 C25 C25 C25 Note 7: SM - Surface Mount, TH - Through Hole FIGURE 16. Capacitor Code Selection Guide www.national.com 20 (Continued) Output Capacitor Cap. Ref. Desg. # Surface Mount Through Hole Sprague AVX TPS Sanyo OS-CON Sanyo MV-GX Nichicon Panasonic 594D Series Series SA Series Series PL Series HFQ Series (F/V) (F/V) (F/V) (F/V) (F/V) (F/V) C1 120/6.3 100/10 100/10 220/35 220/35 220/35 C2 120/6.3 100/10 100/10 150/35 150/35 150/35 C3 120/6.3 100/10 100/35 120/35 120/35 120/35 C4 68/10 100/10 68/10 220/35 220/35 220/35 C5 100/16 100/10 100/10 150/35 150/35 150/35 C6 100/16 100/10 100/10 120/35 120/35 120/35 C7 68/10 100/10 68/10 150/35 150/35 150/35 C8 100/16 100/10 100/10 330/35 330/35 330/35 C9 100/16 100/16 100/16 330/35 330/35 330/35 C10 100/16 100/16 68/16 220/35 220/35 220/35 C11 100/16 100/16 68/16 150/35 150/35 150/35 C12 100/16 100/16 68/16 120/35 120/35 120/35 C13 100/16 100/16 100/16 120/35 120/35 120/35 C14 100/16 100/16 100/16 220/35 220/35 220/35 C15 47/20 68/20 47/20 220/35 220/35 220/35 C16 47/20 68/20 47/20 150/35 150/35 150/35 C17 47/20 68/20 47/20 120/35 120/35 120/35 C18 68/25 (2x) 33/25 47/25 (Note 8) 220/35 220/35 220/35 C19 33/25 33/25 33/25 (Note 8) 150/35 150/35 150/35 C20 33/25 33/25 33/25 (Note 8) 120/35 120/35 120/35 C21 33/35 (2x) 22/25 (Note 9) 150/35 150/35 150/35 C22 33/35 22/35 (Note 9) 120/35 120/35 120/35 C23 (Note 9) (Note 9) (Note 9) 220/50 100/50 120/50 C24 (Note 9) (Note 9) (Note 9) 150/50 100/50 120/50 C25 (Note 9) (Note 9) (Note 9) 150/50 82/50 82/50 Note 8: The SC series of Os-Con capacitors (others are SA series) Note 9: The voltage ratings of the surface mount tantalum chip and Os-Con capacitors are too low to work at these voltages. FIGURE 17. Output Capacitor Selection Table 21 www.national.com LM2674 LM2674 Series Buck Regulator Design Procedure (Adjustable Output) LM2674 Application Information TYPICAL SURFACE MOUNT PC BOARD LAYOUT, FIXED OUTPUT (4X SIZE) 10004136 CIN - 15 F, 25V, Solid Tantalum Sprague, "594D series" COUT - 68 F, 10V, Solid Tantalum Sprague, "594D series" D1 - 1A, 40V Schottky Rectifier, Surface Mount L1 - 47 H, L13, Coilcraft DO3308 CB - 0.01 F, 50V, Ceramic TYPICAL SURFACE MOUNT PC BOARD LAYOUT, ADJUSTABLE OUTPUT (4X SIZE) 10004137 CIN - 15 F, 50V, Solid Tantalum Sprague, "594D series" COUT - 33 F, 25V, Solid Tantalum Sprague, "594D series" D1 - 1A, 40V Schottky Rectifier, Surface Mount L1 - 100 H, L20, Coilcraft DO3316 CB - 0.01 F, 50V, Ceramic R1 - 1k, 1% R2 - Use formula in Design Procedure FIGURE 18. PC Board Layout www.national.com 22 When using the adjustable version, special care must be taken as to the location of the feedback resistors and the associated wiring. Physically locate both resistors near the IC, and route the wiring away from the inductor, especially an open core type of inductor. (Continued) Layout is very important in switching regulator designs. Rapidly switching currents associated with wiring inductance can generate voltage transients which can cause problems. For minimal inductance and ground loops, the wires indicated by heavy lines (in Figure 2 and Figure 3) should be wide printed circuit traces and should be kept as short as possible. For best results, external components should be located as close to the switcher IC as possible using ground plane construction or single point grounding. If open core inductors are used, special care must be taken as to the location and positioning of this type of inductor. Allowing the inductor flux to intersect sensitive feedback, IC ground path, and COUT wiring can cause problems. LLP Package Devices The LM2674 is offered in the 16 lead LLP surface mount package to allow for increased power dissipation compared to the SO-8 and DIP. For details on thermal performance as well as mounting and soldering specifications, refer to Application Note AN-1187. 23 www.national.com LM2674 Application Information LM2674 Physical Dimensions inches (millimeters) unless otherwise noted 8-Lead (0.150" Wide) Molded Small Outline Package, JEDEC Order Number LM2674M-3.3, LM2674M-5.0, LM2674M-12 or LM2674M-ADJ NS Package Number M08A www.national.com 24 LM2674 Physical Dimensions inches (millimeters) unless otherwise noted (Continued) 8-Lead (0.300" Wide) Molded Dual-In-Line Package Order Number LM2674N-3.3, LM2674N-5.0, LM2674N-12 or LM2674N-ADJ NS Package Number N08E 25 www.national.com LM2674 SIMPLE SWITCHER Power Converter High Efficiency 500 mA Step-Down Voltage Regulator Physical Dimensions inches (millimeters) unless otherwise noted (Continued) 16-Lead LLP Surface Mount Package NS Package Number LDA16A LIFE SUPPORT POLICY NATIONAL'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. National Semiconductor Corporation Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: support@nsc.com www.national.com National Semiconductor Europe Fax: +49 (0) 180-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Francais Tel: +33 (0) 1 41 91 8790 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: ap.support@nsc.com National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. National P/N LM2674 - SIMPLE SWITCHER Power Converter High Efficiency 500mA Step-Down Voltage Regulator See A/D Converters Products Products > Analog - Regulators > Simple Switchers > LM2674 LM2674 Product Folder SIMPLE SWITCHER Power Converter High Efficiency 500mA Step-Down Voltage Regulator See Also: LM2671 - Has Sync Pin and softstart, frequency synchronization. Generic P/N 2674 General Description Features WEBENCH Live Simulation! 8.0 <= V out 11.0 V V in Upper <= 1.2 <= I out 13.0 3.3 0.40 Ambient Temperature Samples & Pricing Design Tools Application Notes Parametric Table LM2674 WebenchTM Custom Design/Analyze/Build It V in Lower Package & Models Datasheet 30 V <= 40.0 V <= 40.0 A <= 0.50 C <= 100 Create This Design What is Webench? Multiple Output Capability No On/Off Pin Yes Error Flag No Input Voltage, min (Volt) 15, 6.50 Input Voltage, max (Volt) 40 Output Current, max 500 mA Output Voltage (Volt) 12, 3.30, 5 Adjustable Output Voltage No, Yes Switching Frequency (Hz) 260000 Adjustable Switching Frequency No Sync Pin No Efficiency (%) 94, 86, 90 Flyback No Step-up No Step-down Yes - Datasheet Title LM2674 SIMPLE SWITCHER Power Converter High Efficiency 500 mA Step-Down Voltage Regulator LM2674 SIMPLE SWITCHER Power Converter High Efficiency 500 mA Step-Down Voltage Regulator (JAPANESE) Size in Date Kbytes View Online Download 10494 May- View Online Kbytes 01 Download 271 Kbytes Download View Online Receive via Email Receive via Email Receive via Email file:///H|/imaging/BITTING/cpl/20020808_1/08062002_10/NATL/08062002_HTML/LM2674.html (1 of 5) [Aug-09-2002 2:45:35 PM] National P/N LM2674 - SIMPLE SWITCHER Power Converter High Efficiency 500mA Step-Down Voltage Regulator If you have trouble printing or viewing PDF file(s), see Printing Problems. Package Availability, Models, Samples & Pricing Part Number Package Status Type Budgetary Samples & Pricing Electronic $US Orders SPICE IBIS Qty each Models Pins MSL Std Pack Size Package Marking LM2674LD12 LLP 16 MSL Full production N/A N/A Samples 1K+ $1.2400 reel of 1000 [logo] UZ2T S0009B LM2674LD3.3 LLP 16 MSL Full production N/A N/A Samples 1K+ $1.2400 reel of 1000 [logo] UZ2T S000AB LM2674LD5.0 LLP 16 MSL Full production N/A N/A Samples 1K+ $1.2400 reel of 1000 [logo] UZ2T S000BB LM2674LDADJ LLP 16 MSL Full production N/A N/A Samples 1K+ $1.2400 reel of 1000 [logo] UZ2T S000CB LM2674LDX12 LLP 16 MSL Full production N/A N/A 1K+ $1.2400 reel of 4500 [logo] UZ2T S0009B LM2674LDX3.3 LLP 16 MSL Full production N/A N/A 1K+ $1.2400 reel of 4500 [logo] UZ2T S000AB LM2674LDX5.0 LLP 16 MSL Full production N/A N/A 1K+ $1.2400 reel of 4500 [logo] UZ2T S000BB LM2674LDXADJ LLP 16 MSL Full production N/A N/A 1K+ $1.2400 reel of 4500 [logo] UZ2T S000CB LM2674M-12 SOIC NARROW 8 MSL Full production N/A N/A 1K+ $1.3900 rail of 95 [logo]2T 2674 M-12 LM2674M-3.3 SOIC NARROW 8 MSL Full production N/A N/A 1K+ $1.3900 rail of 95 [logo]2T 2674 M3.3 SOIC LM2674M-5.0 NARROW 8 MSL Full production N/A 24 Hour N/A Samples Buy Now 1K+ $1.3900 rail of 95 [logo]2T 2674 M5.0 LM2674MADJ SOIC NARROW 8 MSL Full production N/A N/A 24 Hour Samples Buy Now 1K+ $1.3900 rail of 95 [logo]2T 2674 MADJ LM2674MX12 SOIC NARROW 8 MSL Full production N/A N/A 1K+ $1.3900 reel of 2500 [logo]2T 2674 M-12 LM2674MX3.3 SOIC NARROW 8 MSL Full production N/A N/A 1K+ $1.3900 reel of 2500 [logo]2T 2674 M3.3 24 Hour Samples Buy Now Samples Buy Now file:///H|/imaging/BITTING/cpl/20020808_1/08062002_10/NATL/08062002_HTML/LM2674.html (2 of 5) [Aug-09-2002 2:45:35 PM] National P/N LM2674 - SIMPLE SWITCHER Power Converter High Efficiency 500mA Step-Down Voltage Regulator 1K+ $1.3900 reel of 2500 [logo]2T 2674 M5.0 1K+ $1.3900 reel of 2500 [logo]2T 2674 MADJ 24 Hour Samples Buy Now 1K+ $1.3900 rail of 40 [logo]UZ2T LM2674 N-12 24 Hour Samples Buy Now 1K+ $1.3900 rail of 40 [logo]UZ2T LM2674 N-3.3 1K+ $1.3900 rail of 40 [logo]UZ2T LM2674 N-5.0 24 Hour Samples Buy Now 1K+ $1.3900 rail of 40 [logo]UZ2T LM2674 N-ADJ Samples gel pak of N/A - Samples gel pak of N/A - Samples gel pak of N/A - Samples gel pak of N/A - N/A wafer jar of N/A - N/A wafer jar of N/A - N/A wafer jar of N/A - N/A wafer jar of N/A - LM2674MX5.0 SOIC NARROW 8 MSL Full production N/A N/A LM2674MXADJ SOIC NARROW 8 MSL Full production N/A N/A LM2674N-12 MDIP 8 MSL Full production N/A N/A LM2674N-3.3 MDIP 8 MSL Full production N/A N/A Buy Now Buy Now LM2674N-5.0 MDIP 8 MSL Full production N/A 24 Hour N/A Samples Buy Now LM2674NADJ MDIP 8 MSL Full production N/A N/A LM2674-12 MDC LM2674-3.3 MDC LM2674-5.0 MDC LM2674-ADJ MDC LM2674-12 MWC LM2674-3.3 MWC LM2674-5.0 MWC LM2674-ADJ MWC Die Die Die Die Wafer Wafer Wafer Wafer Full production Full production Full production Full production Full production Full production Full production Full production N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A General Description file:///H|/imaging/BITTING/cpl/20020808_1/08062002_10/NATL/08062002_HTML/LM2674.html (3 of 5) [Aug-09-2002 2:45:35 PM] National P/N LM2674 - SIMPLE SWITCHER Power Converter High Efficiency 500mA Step-Down Voltage Regulator The LM2674 series of regulators are monolithic integrated circuits built with a LMDMOS process. These regulators provide all the active functions for a step-down (buck) switching regulator, capable of driving a 500 mA load current with excellent line and load regulation. These devices are available in fixed output voltages of 3.3V, 5.0V, 12V, and an adjustable output version. Requiring a minimum number of external components, these regulators are simple to use and include patented internal frequency compensation (Patent Nos. 5,382,918 and 5,514,947) and a fixed frequency oscillator. The LM2674 series operates at a switching frequency of 260 kHz, thus allowing smaller sized filter components than what would be needed with lower frequency switching regulators. Because of its very high efficiency (>90%), the copper traces on the printed circuit board are the only heat sinking needed. A family of standard inductors for use with the LM2674 are available from several different manufacturers. This feature greatly simplifies the design of switch-mode power supplies using these advanced ICs. Also included in the datasheet are selector guides for diodes and capacitors designed to work in switch-mode power supplies. Other features include a guaranteed 1.5% tolerance on output voltage within specified input voltages and output load conditions, and 10% on the oscillator frequency. External shutdown is included, featuring typically 50 A stand-by current. The output switch includes current limiting, as well as thermal shutdown for full protection under fault conditions. To simplify the LM2674 buck regulator design procedure, there exists computer design software, LM267X Made Simple (version 6.0). Features Efficiency up to 96% Available in SO-8, 8-pin DIP and LLP packages Computer Design Software LM267X Made Simple (version 6.0) Simple and easy to design with Requires only 5 external components Uses readily available standard inductors 3.3V, 5.0V, 12V, and adjustable output versions Adjustable version output voltage range: 1.21V to 37V 1.5% max output voltage tolerance over line and load conditions Guaranteed 500mA output load current 0.25 DMOS Output Switch Wide input voltage range: 8V to 40V 260 kHz fixed frequency internal oscillator TTL shutdown capability, low power standby mode Thermal shutdown and current limit protection Applications Simple High Efficiency (>90%) Step-Down (Buck) Regulator Efficient Pre-Regulator for Linear Regulators Positive-to-Negative Converter Design Tools file:///H|/imaging/BITTING/cpl/20020808_1/08062002_10/NATL/08062002_HTML/LM2674.html (4 of 5) [Aug-09-2002 2:45:35 PM] National P/N LM2674 - SIMPLE SWITCHER Power Converter High Efficiency 500mA Step-Down Voltage Regulator Title Size in Kbytes Date SimpleSwitcher(R) DC-DC Converters Design Software 10 Kbytes Receive via View Online Download Email 12-Jun2002 View If you have trouble printing or viewing PDF file(s), see Printing Problems. Application Notes Title Size in Kbytes Date AN-1157: Application Note 1157 Positive to Negative Buck-Boost Converter Using LM267X SIMPLE SWITCHER(R) Regulators 152 Kbytes 8-Nov-00 View Online Download Receive via Email AN-1229: Application Note 1229 SIMPLE SWITCHER PCB Layout Guidelines 229 Kbytes 29-Jul-02 View Online Download Receive via Email View Online Download Receive via Email If you have trouble printing or viewing PDF file(s), see Printing Problems. [Information as of 5-Aug-2002] Search Design Purchasing Quality Company Home About Languages . Website Guide . About "Cookies" . National is QS 9000 Certified . Privacy/Security Statement . Contact Us . Site Terms & Conditions of Use . Copyright 2002 (c) National Semiconductor Corporation . My Preferences . Feedback file:///H|/imaging/BITTING/cpl/20020808_1/08062002_10/NATL/08062002_HTML/LM2674.html (5 of 5) [Aug-09-2002 2:45:35 PM]