Product Folder Sample & Buy Support & Community Tools & Software Technical Documents LM2674 SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 LM2674 SIMPLE SWITCHER(R) Power Converter High Efficiency 500-mA Step-Down Voltage Regulator 1 Features 3 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 3.3 V, 5 V, 12 V, and an adjustable output version. 1 * * * * * * * * * * * * Efficiency up to 96% Available in 8-Pin SOIC, PDIP, and 16-Pin WSON Packages Simple and Easy to Design With Requires Only 5 External Components Uses Readily Available Standard Inductors 3-V, 5-V, 12-V, and Adjustable Output Versions Adjustable Version Output Voltage Range: 1.21 V to 37 V 1.5% Maximum Output Voltage Tolerance Over Line and Load Conditions Ensured 500-mA Output Load Current 0.25- DMOS Output Switch Wide Input Voltage Range: 8 V to 40 V 260-kHz Fixed Frequency Internal Oscillator TTL Shutdown Capability, Low Power Standby Mode Thermal Shutdown and Current Limit Protection 2 Applications * * * Simple High Efficiency (>90%) Step-Down (Buck) Regulators Efficient Preregulator for Linear Regulators Positive-to-Negative Converters Requiring a minimum number of external components, these regulators are simple to use and include patented internal frequency compensation and a fixed frequency oscillator. The LM2674 series operates at a switching frequency of 260 kHz, thus allowing smaller sized filter components than what is required 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 required. 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 data sheet are selector guides for diodes and capacitors designed to work in switch-mode power supplies. Device Information(1) PART NUMBER LM2674 PACKAGE BODY SIZE (NOM) SOIC (8) 4.90 mm x 3.91 mm PDIP (8) 9.81 mm x 6.35 mm WSON (16) 5.00 mm x 5.00 mm (1) For all available packages, see the orderable addendum at the end of the data sheet. Typical Application 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA. LM2674 SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 www.ti.com Table of Contents 1 2 3 4 5 6 7 Features .................................................................. Applications ........................................................... Description ............................................................. Revision History..................................................... Description (continued)......................................... Pin Configuration and Functions ......................... Specifications......................................................... 1 1 1 2 3 3 4 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 4 4 4 4 5 5 5 Absolute Maximum Ratings ...................................... ESD Ratings.............................................................. Recommended Operating Conditions....................... Thermal Information .................................................. Electrical Characteristics - 3.3-V Version................. Electrical Characteristics - 5-V Version.................... Electrical Characteristics - 12-V Version.................. Electrical Characteristics - Adjustable Voltage Version ....................................................................... 7.9 Electrical Characteristics - All Output Voltage Versions ..................................................................... 7.10 Typical Characteristics ............................................ 8 6 6 7 Detailed Description ............................................ 10 8.1 8.2 8.3 8.4 9 Overview ................................................................. Functional Block Diagram ....................................... Feature Description................................................. Device Functional Modes........................................ 10 10 10 11 Application and Implementation ........................ 12 9.1 Application Information............................................ 12 9.2 Typical Applications ................................................ 13 10 Power Supply Recommendations ..................... 24 11 Layout................................................................... 25 11.1 Layout Guidelines ................................................. 25 11.2 Layout Examples................................................... 25 12 Device and Documentation Support ................. 27 12.1 12.2 12.3 12.4 12.5 12.6 Documentation Support ........................................ Receiving Notification of Documentation Updates Community Resources.......................................... Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 27 27 27 27 27 27 13 Mechanical, Packaging, and Orderable Information ........................................................... 27 4 Revision History NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision F (April 2013) to Revision G Page * Added ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section .................................................................................................. 1 * Removed all references to Computer Design Software LM267X Made Simple (Version 6.0).............................................. 1 Changes from Revision E (April 2013) to Revision F * 2 Page Changed layout of National Data Sheet to TI format ........................................................................................................... 25 Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 LM2674 www.ti.com SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 5 Description (continued) Other features include an ensured 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 standby current. The output switch includes current limiting, as well as thermal shutdown for full protection under fault conditions. 6 Pin Configuration and Functions D or P Package 8-Pin SOIC or PDIP Top View CB 1 NC 2 8 7 NHN Package 16-Pin WSON Top View VSW VIN NC 3 6 GND FB 4 5 ON/OFF CB 1 16 VSW NC 2 15 VSW NC 3 14 VIN NC 4 13 NC NC 5 12 GND NC 6 11 GND NC 7 10 NC FB 8 9 DAP ON/OFF Not to scale Not to scale Connect DAP to pin 11 and 12. Pin Functions PIN NAME I/O DESCRIPTION SOIC, PDIP WSON CB 1 1 I Bootstrap capacitor connection for high-side driver. Connect a high-quality, 470-nF capacitor from CB to VSW Pin. FB 4 8 I Feedback sense input pin. Connect to the midpoint of feedback divider to set VOUT for ADJ version or connect this pin directly to the output capacitor for a fixed output version. ON/OFF 5 9 I Enable input to the voltage regulator. High = ON and low = OFF. Pull this pin high or float to enable the regulator VSW 8 15, 16 O Source pin of the internal high-side FET. This is a switching node. Attached this pin to an inductor and the cathode of the external diode GND 6 11, 12 -- Power ground pins. Connect to system ground. Ground pins of CIN and COUT. Path to CIN must be as short as possible. VIN 7 14 I NC 2, 3 2, 3, 4, 5, 6, 7, 10, 13 -- Supply input pin to collector pin of high-side FET. Connect to power supply and input bypass capacitors CIN. Path from VIN pin to high frequency bypass CIN and GND must be as short as possible. No connect pins Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 3 LM2674 SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 www.ti.com 7 Specifications 7.1 Absolute Maximum Ratings over operating free-air temperature range (unless otherwise noted) (1) (2) MIN MAX UNIT 45 V Supply voltage ON/OFF pin voltage, VSH -0.1 6 V -1 V VSW + 8 V 14 V Switch voltage to ground Boost pin voltage Feedback pin voltage, VFB -0.3 Power dissipation Internally Limited D package Lead temperature Vapor phase (60 s) 215 Infrared (15 s) 220 P package (soldering, 10 s) WSON package See AN-1187 Maximum junction temperature Storage temperature, Tstg (1) (2) C 260 -65 150 C 150 C Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and specifications. 7.2 ESD Ratings V(ESD) (1) (2) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1) (2) VALUE UNIT 2000 V JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. The human-body model is a 100-pF capacitor discharged through a 1.5-k resistor into each pin. 7.3 Recommended Operating Conditions MIN MAX Supply voltage 6.5 40 UNIT V Junction temperature, TJ -40 125 C 7.4 Thermal Information LM2674 THERMAL METRIC RJA (1) (2) 4 (1) Junction-to-ambient thermal resistance (2) D (SOIC) P (PDIP) NHN (WSON) 8 PINS 8 PINS 16 PINS 105 95 -- UNIT C/W For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report. Junction to ambient thermal resistance with approximately 1 square inch of printed-circuit board copper surrounding the leads. Additional copper area lowers thermal resistance further. The value RJA for the WSON (NHN) 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 WSON package, see AN-1187 Leadless Leadframe Package (LLP). Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 LM2674 www.ti.com SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 7.5 Electrical Characteristics - 3.3-V Version TJ = 25C (unless otherwise noted) PARAMETER SYSTEM PARAMETERS (see Figure 15) Output voltage VIN = 6.5 V to 40 V, ILOAD = 20 mA to 250 mA Efficiency (1) (2) (3) MAX (1) UNIT (3) VIN = 8 V to 40 V, ILOAD = 20 mA to 500 mA VOUT MIN (1) TYP (2) TEST CONDITIONS TJ = 25C 3.251 TJ = -40C to 125C 3.201 TJ = 25C 3.251 TJ = -40C to 125C 3.201 VIN = 12 V, ILOAD = 500 mA 3.3 3.35 3.399 3.3 3.35 V 3.399 86% All limits are used to calculate Average Outgoing Quality Level (AOQL). Typical numbers are at 25C and represent the most likely norm. 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 Figure 15 and Figure 19, system performance is as specified by the system parameters section of the Electrical Characteristics. 7.6 Electrical Characteristics - 5-V Version TJ = 25C (unless otherwise noted) PARAMETER TEST CONDITIONS SYSTEM PARAMETERS (see Figure 15) VIN = 8 V to 40 V, ILOAD = 20 mA to 500 mA VOUT Output voltage VIN = 6.5 V to 40 V, ILOAD = 20 mA to 250 mA Efficiency (1) (2) (3) MIN (1) TYP (2) MAX (1) 4.925 5 5.075 5 5.075 UNIT (3) TJ = 25C TJ = -40C to 125C TJ = 25C TJ = -40C to 125C 4.85 4.925 5.15 4.85 VIN = 12 V, ILOAD = 500 mA V 5.15 90% All limits are used to calculate Average Outgoing Quality Level (AOQL). Typical numbers are at 25C and represent the most likely norm. 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 Figure 15 and Figure 19, system performance is as specified by the system parameters section of the Electrical Characteristics. 7.7 Electrical Characteristics - 12-V Version TJ = 25C (unless otherwise noted) PARAMETER SYSTEM PARAMETERS (see Figure 15) VOUT Output voltage VIN = 15 V to 40 V, ILOAD = 20 mA to 500 mA Efficiency VIN = 24 V, ILOAD = 500 mA (1) (2) (3) MIN (1) TYP (2) MAX (1) TJ = 25C 11.82 12 12.18 TJ = -40C to 125C 11.64 TEST CONDITIONS UNIT (3) 12.36 V 94% All limits are used to calculate Average Outgoing Quality Level (AOQL). Typical numbers are at 25C and represent the most likely norm. 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 Figure 15 and Figure 19, system performance is as specified by the system parameters section of the Electrical Characteristics. Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 5 LM2674 SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 www.ti.com 7.8 Electrical Characteristics - Adjustable Voltage Version TJ = 25C (unless otherwise noted) MIN (1) TYP (2) MAX (1) TJ = 25C 1.192 1.21 1.228 TJ = -40C to 125C 1.174 VIN = 6.5 V to 40 V, ILOAD = 20 mA to 250 mA, TJ = 25C VOUT programmed for 5 V (see Figure 19) TJ = -40C to 125C 1.192 PARAMETER TEST CONDITIONS SYSTEM PARAMETERS (see Figure 19) VIN = 8 V to 40 V, ILOAD = 20 mA to 500 mA, VOUT programmed for 5 V (see Figure 19) VFB Feedback voltage Efficiency (1) (2) (3) UNIT (3) 1.246 1.21 1.174 VIN = 12 V, ILOAD = 500 mA V 1.228 1.246 90% All limits are used to calculate Average Outgoing Quality Level (AOQL). Typical numbers are at 25C and represent the most likely norm. 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 Figure 15 and Figure 19, system performance is as specified by the system parameters section of the Electrical Characteristics. 7.9 Electrical Characteristics - All Output Voltage Versions TJ = 25C, VIN = 12 V for the 3.3-V, 5-V, and adjustable versions and VIN = 24 V for the 12-V version, and ILOAD = 100 mA (unless otherwise noted) PARAMETERS TEST CONDITIONS MIN TYP MAX VFEEDBACK = 8 V for 3.3-V, 5-V, and adjustable voltage versions 2.5 3.6 VFEEDBACK = 15 V for 12-V versions 2.5 UNIT DEVICE PARAMETERS IQ Quiescent current ISTBY Standby quiescent current ICL Current limit IL Output leakage current ON/OFF pin = 0 V 1 TJ = 25C A 6 15 mA 0.25 0.4 TJ = -40C to 125C 0.6 TJ = 25C 260 TJ = -40C to 125C 225 VFEEDBACK = 1.3 V (adjustable version only) IS/D ON/OFF pin current ON/OFF pin = 0 V kHz 275 0% Turnon threshold, rising (1) 85 TJ = 25C nA 1.4 TJ = -40C to 125C 0.8 TJ = 25C 2 20 TJ = -40C to 125C A 25 Minimum duty cycle Feedback bias current 1.2 A 1.25 95% ON/OFF pin voltage threshold 6 0.8 Maximum duty cycle VS/D (1) 0.62 0.575 VSWITCH = -1 V, ON/OFF pin = 0 V Measured at switch pin mA 100 150 VIN = 40 V, ON/OFF pin = 0 V, VSWITCH = 0 V fO IBIAS TJ = -40C to 125C TJ = -40C to 125C ISWITCH = 500 mA D 50 TJ = 25C RDS(ON) Switch ON-resistance Oscillator frequency TJ = 25C mA 7 37 V A The ON/OFF pin is internally pulled up to 7 V and can be left floating for always-on operation. Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 LM2674 www.ti.com SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 7.10 Typical Characteristics Figure 1. Normalized Output Voltage Figure 2. Line Regulation Figure 3. Efficiency Figure 4. Drain-to-Source Resistance Figure 5. Switch Current Limit Figure 6. Operating Quiescent Current Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 7 LM2674 SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 www.ti.com Typical Characteristics (continued) 8 Figure 7. Standby Quiescent Current Figure 8. ON/OFF Threshold Voltage Figure 9. ON/OFF Pin Current (Sourcing) Figure 10. Switching Frequency Figure 11. Feedback Pin Bias Current Figure 12. Peak Switch Current Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 LM2674 www.ti.com SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 Typical Characteristics (continued) Figure 13. Dropout Voltage, 3.3-V Version Figure 14. Dropout Voltage, 5-V Version Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 9 LM2674 SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 www.ti.com 8 Detailed Description 8.1 Overview The LM2674 SIMPLE SWITCHER(R) regulator is an easy-to-use non-synchronous step-down DC-DC converter with a wide input voltage range up to 40 V. It is capable of delivering up to 0.5-A DC load current with excellent line and load regulation. These devices are available in fixed output voltages of 3.3 V, 5 V, 12 V, and an adjustable output version. The family requires few external components and the pin arrangement was designed for simple, optimum PCB layout. 8.2 Functional Block Diagram 8.3 Feature Description 8.3.1 Adjustable Output Voltage The voltage regulation loop in the LM2674 regulates output voltage by maintaining the voltage on FB pin (VFB) to be the same as the internal REF voltage (VREF). A resistor divider pair is required to program the ratio from output voltage VOUT to VFB. The resistor is connected from the VOUT of the LM2674 to ground with the midpoint connecting to the FB pin. The voltage reference system produces a precise voltage reference over temperature. The internal REF voltage is 1.21 V typically. To program the output voltage of the LM2674 to be a certain value VOUT, R1 can be calculated with a selected R2 (see Adjustable Output Voltage Typical Application). R2 is in the range from 10 k to 100 k is recommended for most applications. If the resistor 10 Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 LM2674 www.ti.com SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 Feature Description (continued) divider is not connected properly, output voltage cannot be regulated because the feedback loop is broken. If the FB pin is shorted to ground, the output voltage is driven close to VIN, because the regulator sees very low voltage on the FB pin and tries to regulator it up. The load connected to the output could be damaged under such a condition. Do not short FB pin to ground when the LM2674 is enabled. It is important to route the feedback trace away from the noisy area of the PCB. For more layout recommendations, see Layout. 8.4 Device Functional Modes 8.4.1 Shutdown Mode The ON/OFF pin provides electrical ON and OFF control for the LM2674. When the voltage of this pin is lower than 1.4 V, the device is in shutdown mode. The typical standby current in this mode is 50 A. 8.4.2 Active Mode When the voltage of the ON/OFF pin is higher than 1.4 V, the device starts switching and the output voltage rises until it reaches a normal regulation voltage. Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 11 LM2674 SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 www.ti.com 9 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI's customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 9.1 Application Information The LM2674 is a step-down DC-DC regulator. It is typically used to convert a higher DC voltage to a lower DC voltage with a maximum output current of 0.5 A. The following design procedure can be used to select components for the LM2674. Alternately, the WEBENCH(R) software may be used to generate complete designs. When generating a design, the WEBENCH software uses iterative design procedure and accesses comprehensive databases of components. See ti.com for more details. When the output voltage is greater than approximately 6 V, and the duty cycle at minimum input voltage is greater than approximately 50%, the designer must exercise caution in selection of the output filter components. When an application designed to these specific operating conditions is subjected to a current limit fault condition, it may be possible to observe a large hysteresis in the current limit. This can affect the output voltage of the device until the load current is reduced sufficiently to allow the current limit protection circuit to reset itself. Under current limiting conditions, the LM267x is designed to respond in the following manner: 1. At the moment when the inductor current reaches the current limit threshold, the ON-pulse is immediately terminated. This happens for any application condition. 2. However, the current limit block is also designed to momentarily reduce the duty cycle to below 50% to avoid subharmonic oscillations, which could cause the inductor to saturate. 3. Thereafter, once the inductor current falls below the current limit threshold, there is a small relaxation time during which the duty cycle progressively rises back above 50% to the value required to achieve regulation. If the output capacitance is sufficiently large, it may be possible that as the output tries to recover, the output capacitor charging current is large enough to repeatedly re-trigger the current limit circuit before the output has fully settled. This condition is exacerbated with higher output voltage settings because the energy requirement of the output capacitor varies as the square of the output voltage (1/2 CV2), thus requiring an increased charging current. A simple test to determine if this condition might exist for a suspect application is to apply a short circuit across the output of the converter, and then remove the shorted output condition. In an application with properly selected external components, the output recovers smoothly. Practical values of external components that have been experimentally found to work well under these specific operating conditions are COUT = 47 F, L = 22 H. NOTE Even with these components, for a device's current limit of ICLIM, the maximum load current under which the possibility of the large current limit hysteresis can be minimized is ICLIM/2. For example, if the input is 24 V and the set output voltage is 18 V, then for a desired maximum current of 1.5 A, the current limit of the chosen switcher must be confirmed to be at least 3 A. Under extreme overcurrent or shortcircuit conditions, the LM267X employs frequency foldback in addition to the current limit. If the cycle-by-cycle inductor current increases above the current limit threshold (due to short circuit or inductor saturation for example) the switching frequency is automatically reduced to protect the IC. Frequency below 100 kHz is typical for an extreme short-circuit condition. 12 Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 LM2674 www.ti.com SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 9.2 Typical Applications 9.2.1 Fixed Output Voltage Typical Application CIN = 22-F, 50-V Tantalum, Sprague 199D Series COUT = 47-F, 25-V Tantalum, Sprague 595D Series D1 = 3.3-A, 50-V Schottky Rectifier, IR 30WQ05F L1 = 68-H Sumida #RCR110D-680L CB = 0.01-F, 50-V Ceramic Figure 15. Fixed Output Voltage Version 9.2.1.1 Design Requirements Table 1 lists the design parameters of this example. Table 1. Design Parameters PARAMETER VALUE Regulated output voltage (3.3 V, 5 V, or 12 V), VOUT 5V Maximum DC input voltage, VIN(max) 12 V Maximum load current, ILOAD(max) 500 mA 9.2.1.2 Detailed Design Procedure 9.2.1.2.1 Inductor Selection (L1) 1. Select the correct inductor value selection guide from Figure 24, Figure 25, or Figure 26 (output voltages of 3.3 V, 5 V, or 12 V respectively). For all other voltages, see the design procedure for the adjustable version. Use the inductor selection guide for the 5-V version shown in Figure 25. 2. 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). From the inductor value selection guide shown in Figure 25, the inductance region intersected by the 12-V horizontal line and the 500-mA vertical line is 47 H, and the inductor code is L13. 3. Select an appropriate inductor from the four manufacturer's part numbers listed in Table 7. 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: - 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 Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 13 LM2674 SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 www.ti.com 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. The inductance value required is 47 H. From Table 7, 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). 9.2.1.2.2 Output Capacitor Selection (COUT) Select an output capacitor from the output capacitor Table 2. Using the output voltage and the inductance value found in the inductor selection guide, step 1, locate the appropriate capacitor value and voltage rating. Use the 5-V section in the output capacitor Table 2. 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 following: * Surface mount - 68-F, 10-V Sprague 594D series - 100-F, 10-V AVX TPS series * Through hole - 68-F, 10-V Sanyo OS-CON SA series - 150-F, 35-V Sanyo MV-GX series - 150-F, 35-V Nichicon PL series - 150-F, 35-V Panasonic HFQ series The capacitor list contains through-hole electrolytic capacitors from four different capacitor manufacturers and surface-mount tantalum capacitors from two different capacitor manufacturers. TI recommends that both the manufacturers and the manufacturer's series that are listed in the table be used. Table 2. Output Capacitor Table OUTPUT CAPACITOR OUTPUT VOLTAGE (V) 3.3 5 12 14 INDUCTANCE (H) SURFACE MOUNT THROUGH HOLE SPRAGUE 594D SERIES (F/V) AVX TPS SERIES (F/V) SANYO OS-CON SA SERIES (F/V) SANYO MV-GX SERIES (F/V) NICHICON PL SERIES (F/V) PANASONIC HFQ SERIES (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 Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 LM2674 www.ti.com SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 9.2.1.2.3 Catch Diode Selection (D1) 1. 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 must 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. Refer to Table 3. In this example, a 1-A, 20-V Schottky diode provides the best performance. If the circuit must withstand a continuous shorted output, a higher current Schottky diode is recommended. Table 3. Schottky Diode Selection Table 500-mA DIODES 3-A DIODES VR SURFACE MOUNT THROUGHHOLE SURFACE MOUNT THROUGHHOLE 20V SK12 1N5817 SK32 1N5820 B120 SR102 30V SK13 1N5818 SK33 1N5821 B130 11DQ03 30WQ03F 31DQ03 40V SR302 MBRS130 SR103 SK14 1N5819 SK34 1N5822 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 2. The reverse voltage rating of the diode must be at least 1.25 times the maximum input voltage. 3. Because of their fast switching speed and low forward voltage drop, Schottky diodes provide the best performance and efficiency. This Schottky diode must be placed close to the LM2674 using short leads and short printed-circuit traces. 9.2.1.2.4 Input Capacitor (CIN) A low ESR aluminum or tantalum bypass capacitor is required between the input pin and ground to prevent large voltage transients from appearing at the input. This capacitor must be placed close to the IC using short leads. In addition, the RMS current rating of the input capacitor must be selected to be at least 1/2 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 16 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. Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 15 LM2674 SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 www.ti.com Figure 16. RMS Current Ratings for Low ESR Electrolytic Capacitors (Typical) For an aluminum electrolytic capacitor, the voltage rating must 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 must be twice the maximum input voltage. Table 4 and Table 5 show the recommended application voltage for AVX TPS and Sprague 594D tantalum capacitors. TI recommends 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. Table 4. AVX TPS (1) RECOMMENDED APPLICATION VOLTAGE VOLTAGE RATING 85C RATING (1) 3.3 6.3 5 10 10 20 12 25 15 35 Recommended Application Voltage for AVX TPS and Sprague 594D Tantalum Chip Capacitors Derated for 85C Table 5. Sprague 594D (1) RECOMMENDED APPLICATION VOLTAGE VOLTAGE RATING 85C RATING (1) 16 2.5 4 3.3 6.3 5 10 8 16 12 20 18 25 24 35 29 50 Recommended Application Voltage for AVX TPS and Sprague 594D Tantalum Chip Capacitors Derated for 85C Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 LM2674 www.ti.com SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 Use caution when using only 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 12 V, an aluminum electrolytic capacitor with a voltage rating greater than 15 V (1.25 x VIN) is required. The next higher capacitor voltage rating is 16 V. The RMS current rating requirement for the input capacitor in a buck regulator is approximately 1/2 the DC load current. In this example, with a 500-mA load, a capacitor with an RMS current rating of at least 250 mA is required. The curves shown in Figure 16 can be used to select an appropriate input capacitor. From the curves, locate the 16-V line and note which capacitor values have RMS current ratings greater than 250 mA. For a through-hole design, a 100-F, 16-V electrolytic capacitor (Panasonic HFQ series, Nichicon PL, Sanyo MVGX 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 Table 4, and the Sprague 594D series datasheet, a Sprague 594D 15-F, 25-V capacitor is adequate. 9.2.1.2.5 Boost Capacitor (CB) This capacitor develops the necessary voltage to turn the switch gate on fully. All applications must use a 0.01-F, 50-V ceramic capacitor. For this application, and all applications, use a 0.01-F, 50-V ceramic capacitor. 9.2.1.3 Application Curves Continuous mode switching waveforms VIN = 20 V, VOUT = 5 V, ILOAD = 500 mA L = 100 H, COUT = 100 F, COUTESR = 0.1 A: VSW pin voltage = 10 V/div B: Inductor current = 0.2 A/div C: Output ripple voltage = 50 mV/div ac-coupled Load transient response for continuous mode VIN = 20 V, VOUT = 5 V, L = 100 H, COUT = 100 F, COUTESR = 0.1 A: Output voltage = 100 mV/div, ac-coupled B: Load current = 100-mA to 500-mA load pulse Figure 17. Horizontal Time Base: 1 s/div Figure 18. Horizontal Time Base: 50 s/div Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 17 LM2674 SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 www.ti.com 9.2.2 Adjustable Output Voltage Typical Application CIN = 22-F, 50-V Tantalum, Sprague 199D Series COUT = 47-F, 25-V Tantalum, Sprague 595D Series D1 = 3.3-A, 50-V Schottky Rectifier, IR 30WQ05F L1 = 68-H Sumida #RCR110D-680L R1 = 1.5 k, 1% CB = 0.01-F, 50-V Ceramic For a 5-V output, select R2 to be 4.75 k, 1% where VREF = 1.21 V Use a 1% resistor for best stability. Figure 19. Adjustable Output Voltage Version 9.2.2.1 Design Requirements Table 6 lists the design parameters of this example. Table 6. Design Parameters PARAMETER VALUE Regulated output voltage, VOUT 20 Maximum input voltage, VIN(max) 28 Maximum load current, ILOAD(max) 500 Switching frequency, F Fixed at a nominal 260 kHz 9.2.2.2 Detailed Design Procedure 9.2.2.2.1 Programming Output Voltage Select R1 and R2, as shown in Figure 19. Use the following formula to select the appropriate resistor values. where * VREF = 1.21 V (1) Select a value for R1 between 240 and 1.5 k. The lower resistor values minimize noise pickup in the sensitive feedback pin. (For the lowest temperature coefficient and the best stability with time, use 1% metal film resistors.) 18 Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 LM2674 www.ti.com SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 (2) Select R1 to be 1 k, 1%. Solve for R2. where * R2 = 1k (16.53 - 1) = 15.53 k, closest 1% value is 15.4 k R2 = 15.4 k (3) 9.2.2.2.2 Inductor Selection (L1) 1. Calculate the inductor Volt * microsecond constant E * T (V * s) from Equation 4. where * * VSAT = internal switch saturation voltage = 0.25 V VD = diode forward voltage drop = 0.5 V (4) Calculate the inductor Volt * microsecond constant (E * T) with Equation 5. (5) 2. 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 27. E * T = 21.6 (V * s) 3. On the horizontal axis, select the maximum load current. ILOAD(max) = 500 mA 4. 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). From the inductor value selection guide shown in Figure 27, the inductance region intersected by the 21.6 (V * s) horizontal line and the 500-mA vertical line is 100 H, and the inductor code is L20. 5. Select an appropriate inductor from the four manufacturer's part numbers listed in Table 7. For information on the different types of inductors, see the inductor selection in the fixed output voltage design procedure. From Table 7, locate line L20, and select an inductor part number from the list of manufacturers' part numbers. Table 7. Inductor Manufacturers' Part Numbers IND. REF. DESG. INDUCTANCE (H) CURRENT (A) L2 150 L3 100 L4 SCHOTT RENCO PULSE ENGINEERING COILCRAFT THROUGH HOLE SURFACE MOUNT THROUGH HOLE SURFACE MOUNT THROUGH HOLE SURFACE MOUNT SURFACE MOUNT 0.21 67143920 67144290 RL-5470-4 RL1500-150 PE-53802 PE-53802-S DO1608-154 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 PE-53812 PE-53812-S DO3308-683 L13 47 0.7 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 Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 19 LM2674 SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 www.ti.com Table 7. Inductor Manufacturers' Part Numbers (continued) IND. REF. DESG. INDUCTANCE (H) CURRENT (A) L15 22 L18 220 L19 SCHOTT RENCO THROUGH HOLE SURFACE MOUNT THROUGH HOLE 0.99 67148350 67148460 0.55 67144040 67144420 150 0.66 67144050 L20 100 0.82 L21 68 0.99 PULSE ENGINEERING COILCRAFT SURFACE MOUNT THROUGH HOLE SURFACE MOUNT SURFACE MOUNT RL-1284-22-43 RL1500-22 PE-53815 PE-53815-S DO3308-223 RL-5471-2 RL1500-220 PE-53818 PE-53818-S DO3316-224 67144430 RL-5471-3 RL1500-150 PE-53819 PE-53819-S DO3316-154 67144060 67144440 RL-5471-4 RL1500-100 PE-53820 PE-53820-S DO3316-104 67144070 67144450 RL-5471-5 RL1500-68 PE-53821 PE-53821-S DO3316-683 9.2.2.2.3 Output Capacitor Selection (COUT) 1. Select an output capacitor from the capacitor code selection guide in Table 8. Using the inductance value found in the inductor selection guide, step 1, locate the appropriate capacitor code corresponding to the desired output voltage. Use the appropriate row of the capacitor code selection guide, in Table 8. For this example, use the 15-V to 20-V row. The capacitor code corresponding to an inductance of 100 H is C20. 2. Select an appropriate capacitor value and voltage rating, using the capacitor code, from the output capacitor selection in Table 9. There are two solid tantalum (surface-mount) capacitor manufacturers and four electrolytic (through-hole) capacitor manufacturers to choose from. TI recommends that both the manufacturers and the manufacturer's series that are listed in the table be used. From the output capacitor selection in Table 9, 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 following: - Surface mount - 33-F, 25-V Sprague 594D series - 33-F, 25-V AVX TPS series - Through hole - 33-F, 25-V Sanyo OS-CON SC series - 120-F, 35-V Sanyo MV-GX series - 120-F, 35-V Nichicon PL series - 20-F, 35-V 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. Table 8. Capacitor Code Selection Guide (1) 20 INDUCTANCE (H) CASE STYLE (1) OUTPUT VOLTAGE (V) 22 33 47 68 100 150 220 SM and TH 1.21-2.5 -- -- -- -- C1 C2 C3 SM and TH 2.5-3.75 -- -- -- C1 C2 C3 C3 SM and TH 3.75-5 -- -- C4 C5 C6 C6 C6 SM and TH 5-6.25 -- 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 C9 C10 C11 C12 C13 C13 C13 SM and TH 10-12.5 C14 C11 C12 C12 C13 C13 C13 SM and TH 12.5-15 C15 C16 C17 C17 C17 C17 C17 SM and TH 15-20 C18 C19 C20 C20 C20 C20 C20 SM and TH 20-30 C21 C22 C22 C22 C22 C22 C22 TH 30-37 C23 C24 C24 C25 C25 C25 C25 SM = Surface mount and TH = Through hole Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 LM2674 www.ti.com SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 Table 9. Output Capacitor Selection Table OUTPUT CAPACITOR SURFACE MOUNT THROUGH HOLE CAP. REF. DESG. # SPRAGUE 594D SERIES (F/V) AVX TPS SERIES (F/V) SANYO OS-CON SA SERIES (F/V) SANYO MV-GX SERIES (F/V) NICHICON PL SERIES (F/V) PANASONIC HFQ SERIES (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 (1) (2) 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/ (1) 220/35 220/35 220/35 (1) C19 33/25 33/25 33/25 150/35 150/35 150/35 C20 33/25 33/25 33/25 (1) 120/35 120/35 120/35 C21 33/35 (2x) 22/25 See (2) 150/35 150/35 150/35 (2) C22 33/35 22/35 See 120/35 120/35 120/35 C23 See (2) See (2) See (2) 220/50 100/50 120/50 C24 See (2) See (2) See (2) 150/50 100/50 120/50 C25 (2) (2) (2) 150/50 82/50 82/50 See See See The SC series of Os-Con capacitors (others are SA series) The voltage ratings of the surface mount tantalum chip and Os-Con capacitors are too low to work at these voltages. 9.2.2.2.4 Catch Diode Selection (D1) 1. 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 must 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. Schottky diodes provide the best performance, and in this example a 500-mA, 40-V Schottky diode would be a good choice. If the circuit must withstand a continuous shorted output, a higher current (at least 1.2 A) Schottky diode is recommended. 2. The reverse voltage rating of the diode must be at least 1.25 times the maximum input voltage. 3. Because of their fast switching speed and low forward voltage drop, Schottky diodes provide the best performance and efficiency. The Schottky diode must be placed close to the LM2674 using short leads and short printed-circuit traces. Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 21 LM2674 SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 www.ti.com 9.2.2.2.5 Input Capacitor (CIN) A low ESR aluminum or tantalum bypass capacitor is required between the input pin and ground to prevent large voltage transients from appearing at the input. This capacitor must be placed close to the IC using short leads. In addition, the RMS current rating of the input capacitor must be selected to be at least 1/2 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 16 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. Figure 20. RMS Current Ratings for Low ESR Electrolytic Capacitors (Typical) For an aluminum electrolytic capacitor, the voltage rating must 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 must be twice the maximum input voltage. Table 10 and Table 5 show the recommended application voltage for AVX TPS and Sprague 594D tantalum capacitors. TI also recommends 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. Table 10. AVX TPS (1) RECOMMENDED APPLICATION VOLTAGE VOLTAGE RATING 85C RATING (1) 3.3 6.3 5 10 10 20 12 25 15 35 Recommended Application Voltage for AVX TPS and Sprague 594D Tantalum Chip Capacitors Derated for 85C Table 11. Sprague 594D (1) RECOMMENDED APPLICATION VOLTAGE VOLTAGE RATING 85C RATING (1) 22 2.5 4 3.3 6.3 5 10 8 16 12 20 Recommended Application Voltage for AVX TPS and Sprague 594D Tantalum Chip Capacitors Derated for 85C Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 LM2674 www.ti.com SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 Table 11. Sprague 594D() (continued) RECOMMENDED APPLICATION VOLTAGE VOLTAGE RATING 85C RATING 18 25 24 35 29 50 Use caution when using only 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 28 V, an aluminum electrolytic capacitor with a voltage rating of at least 35 V (1.25 x VIN) is required. The RMS current rating requirement for the input capacitor in a buck regulator is approximately 1/2 the DC load current. In this example, with a 500-mA load, a capacitor with an RMS current rating of at least 250 mA is required. The curves shown in Figure 16 can be used to select an appropriate input capacitor. From the curves, locate the 35-V line and note which capacitor values have RMS current ratings greater than 250 mA. For a through-hole design, a 68-F, 35-V electrolytic capacitor (Panasonic HFQ series, Nichicon PL, Sanyo MVGX 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 note 1 of Table 5, and the Sprague 594D series datasheet, a Sprague 594D 15-F, 50-V capacitor is adequate. 9.2.2.2.6 Boost Capacitor (CB) This capacitor develops the necessary voltage to turn the switch gate on fully. All applications must use a 0.01-F, 50-V ceramic capacitor. For this application, and all applications, use a 0.01-F, 50-V ceramic capacitor. 9.2.2.3 Application Curves Discontinuous mode switching waveforms VIN = 20 V, VOUT = 5 V, ILOAD = 300 mA, L = 15 H, COUT = 68 F (2x), COUTESR = 25 m A: VSW pin voltage = 10 V/div B: Inductor current = 0.5 A/div C: Output ripple voltage = 20 mV/div ac-coupled Load transient response for discontinuous mode VIN = 20 V, VOUT = 5 V, L = 47 H, COUT = 68 F, COUTESR = 50 m A: Output voltage = 100 mV/div, ac-coupled B: Load current = 100-mA to 400-mA load pulse Figure 21. Horizontal Time Base: 1 s/div Figure 22. Horizontal Time Base: 200 s/div Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 23 LM2674 SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 www.ti.com 9.2.3 Typical Application for All Output Voltage Versions Figure 23. Typical Application 9.2.3.1 Application Curves for continuous mode operation Figure 24. LM2674, 3.3-V Version Figure 25. LM2674, 5-V Version Figure 26. LM2674, 12-V Version Figure 27. LM2674, Adjustable Version 10 Power Supply Recommendations The LM2674 is designed to operate from an input voltage supply up to 40 V. This input supply must be well regulated and able to withstand maximum input current and maintain a stable voltage. 24 Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 LM2674 www.ti.com SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 11 Layout 11.1 Layout Guidelines 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 15 and Figure 19) must be wide printed-circuit traces and must be kept as short as possible. For best results, external components must be placed as close to the switcher IC as possible using ground plane construction or single point grounding. If open core inductors are used, take special care 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. When using the adjustable version, take special care as to the location of the feedback resistors and the associated wiring. Physically place both resistors near the IC, and route the wiring away from the inductor, especially an open core type of inductor. 11.1.1 WSON Package Devices The LM2674 is offered in the 16-pin WSON surface mount package to allow for increased power dissipation compared to the 8-pin SOIC and PDIP. The die attach pad (DAP) must be connected to PCB ground plane. For CAD and assembly guidelines refer to AN-1187 Leadless Leadfram Package (LLP). 11.2 Layout Examples CIN = 15-F, 25-V, Solid Tantalum Sprague 594D series COUT = 68-F, 10-V, Solid Tantalum Sprague 594D series D1 = 1-A, 40-V Schottky Rectifier, Surface Mount L1 = 47-H, L13, Coilcraft DO3308 CB = 0.01-F, 50-V Ceramic Figure 28. Typical Surface-Mount PCB Layout, Fixed Output (4x Size) Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 25 LM2674 SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 www.ti.com Layout Examples (continued) CIN = 15-F, 50-V, Solid Tantalum Sprague 594D series COUT = 33-F, 25-V, Solid Tantalum Sprague 594D series D1 = 1-A, 40-V Schottky Rectifier, Surface Mount L1 = 100-H, L20, Coilcraft DO3316 CB = 0.01-F, 50-V Ceramic R1 = 1k, 1% R2 = Use formula in Detailed Design Procedure Figure 29. Typical Surface-Mount PCB Layout, Adjustable Output (4x Size) 26 Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 LM2674 www.ti.com SNVS007G - SEPTEMBER 1998 - REVISED JUNE 2016 12 Device and Documentation Support 12.1 Documentation Support 12.1.1 Related Documentation For related documentation see the following: AN-1187 Leadless Leadfram Package (LLP) 12.2 Receiving Notification of Documentation Updates To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper right corner, click on Alert me to register and receive a weekly digest of any product information that has changed. For change details, review the revision history included in any revised document. 12.3 Community Resources The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of Use. TI E2ETM Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow engineers. Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and contact information for technical support. 12.4 Trademarks E2E is a trademark of Texas Instruments. SIMPLE SWITCHER, WEBENCH are registered trademarks of Texas Instruments. All other trademarks are the property of their respective owners. 12.5 Electrostatic Discharge Caution 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. 12.6 Glossary SLYZ022 -- TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 13 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation. Submit Documentation Feedback Copyright (c) 1998-2016, Texas Instruments Incorporated Product Folder Links: LM2674 27 PACKAGE OPTION ADDENDUM www.ti.com 11-Jan-2021 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (C) Device Marking (3) (4/5) (6) LM2674LD-ADJ/NOPB ACTIVE WSON NHN 16 1000 RoHS & Green SN Level-3-260C-168 HR -40 to 125 S000CB LM2674LDX-5.0/NOPB ACTIVE WSON NHN 16 4500 RoHS & Green SN Level-3-260C-168 HR -40 to 125 S000BB LM2674M-12 NRND SOIC D 8 95 Non-RoHS & Green Call TI Call TI -40 to 125 2674 M-12 LM2674M-12/NOPB ACTIVE SOIC D 8 95 RoHS & Green Call TI | SN Level-1-260C-UNLIM -40 to 125 2674 M-12 LM2674M-3.3/NOPB ACTIVE SOIC D 8 95 RoHS & Green Call TI | SN Level-1-260C-UNLIM -40 to 125 2674 M3.3 LM2674M-5.0 NRND SOIC D 8 95 Non-RoHS & Green Call TI Call TI -40 to 125 2674 M5.0 LM2674M-5.0/NOPB ACTIVE SOIC D 8 95 RoHS & Green Call TI | SN Level-1-260C-UNLIM -40 to 125 2674 M5.0 LM2674M-ADJ/NOPB ACTIVE SOIC D 8 95 RoHS & Green Call TI | SN Level-1-260C-UNLIM -40 to 125 2674 MADJ LM2674MX-12/NOPB ACTIVE SOIC D 8 2500 RoHS & Green Call TI | SN Level-1-260C-UNLIM -40 to 125 2674 M-12 LM2674MX-3.3/NOPB ACTIVE SOIC D 8 2500 RoHS & Green Call TI | SN Level-1-260C-UNLIM -40 to 125 2674 M3.3 LM2674MX-5.0/NOPB ACTIVE SOIC D 8 2500 RoHS & Green Call TI | SN Level-1-260C-UNLIM -40 to 125 2674 M5.0 LM2674MX-ADJ/NOPB ACTIVE SOIC D 8 2500 RoHS & Green Call TI | SN Level-1-260C-UNLIM -40 to 125 2674 MADJ LM2674N-3.3/NOPB ACTIVE PDIP P 8 40 RoHS & Green SN Level-1-NA-UNLIM -40 to 125 LM2674 N-3.3 LM2674N-5.0/NOPB ACTIVE PDIP P 8 40 RoHS & Green SN Level-1-NA-UNLIM -40 to 125 LM2674 N-5.0 LM2674N-ADJ/NOPB ACTIVE PDIP P 8 40 RoHS & Green SN Level-1-NA-UNLIM -40 to 125 LM2674 N-ADJ (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 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 11-Jan-2021 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) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based flame retardants must also meet the <=1000ppm threshold requirement. (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device 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 Device Marking for that device. (6) Lead finish/Ball material - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead finish/Ball material values may wrap to two lines if the finish value exceeds the maximum column width. 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 2 PACKAGE MATERIALS INFORMATION www.ti.com 8-Mar-2019 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 LM2674LD-ADJ/NOPB WSON NHN 16 1000 178.0 12.4 5.3 5.3 1.3 8.0 12.0 Q1 LM2674LDX-5.0/NOPB WSON NHN 16 4500 330.0 12.4 5.3 5.3 1.3 8.0 12.0 Q1 LM2674MX-12/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM2674MX-3.3/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM2674MX-5.0/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM2674MX-ADJ/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 8-Mar-2019 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM2674LD-ADJ/NOPB WSON NHN 16 1000 210.0 185.0 35.0 LM2674LDX-5.0/NOPB WSON NHN 16 4500 367.0 367.0 35.0 LM2674MX-12/NOPB SOIC D 8 2500 367.0 367.0 35.0 LM2674MX-3.3/NOPB SOIC D 8 2500 367.0 367.0 35.0 LM2674MX-5.0/NOPB SOIC D 8 2500 367.0 367.0 35.0 LM2674MX-ADJ/NOPB SOIC D 8 2500 367.0 367.0 35.0 Pack Materials-Page 2 PACKAGE OUTLINE D0008A SOIC - 1.75 mm max height SCALE 2.800 SMALL OUTLINE INTEGRATED CIRCUIT C SEATING PLANE .228-.244 TYP [5.80-6.19] A .004 [0.1] C PIN 1 ID AREA 6X .050 [1.27] 8 1 2X .150 [3.81] .189-.197 [4.81-5.00] NOTE 3 4X (0 -15 ) 4 5 B 8X .012-.020 [0.31-0.51] .010 [0.25] C A B .150-.157 [3.81-3.98] NOTE 4 .069 MAX [1.75] .005-.010 TYP [0.13-0.25] 4X (0 -15 ) SEE DETAIL A .010 [0.25] .004-.010 [0.11-0.25] 0 -8 .016-.050 [0.41-1.27] DETAIL A (.041) [1.04] TYPICAL 4214825/C 02/2019 NOTES: 1. Linear dimensions are in inches [millimeters]. Dimensions in parenthesis are for reference only. Controlling dimensions are in inches. Dimensioning and tolerancing per ASME Y14.5M. 2. This drawing is subject to change without notice. 3. This dimension does not include mold flash, protrusions, or gate burrs. Mold flash, protrusions, or gate burrs shall not exceed .006 [0.15] per side. 4. This dimension does not include interlead flash. 5. Reference JEDEC registration MS-012, variation AA. www.ti.com EXAMPLE BOARD LAYOUT D0008A SOIC - 1.75 mm max height SMALL OUTLINE INTEGRATED CIRCUIT 8X (.061 ) [1.55] SYMM SEE DETAILS 1 8 8X (.024) [0.6] 6X (.050 ) [1.27] SYMM 5 4 (R.002 ) TYP [0.05] (.213) [5.4] LAND PATTERN EXAMPLE EXPOSED METAL SHOWN SCALE:8X METAL SOLDER MASK OPENING EXPOSED METAL .0028 MAX [0.07] ALL AROUND SOLDER MASK OPENING METAL UNDER SOLDER MASK EXPOSED METAL .0028 MIN [0.07] ALL AROUND SOLDER MASK DEFINED NON SOLDER MASK DEFINED SOLDER MASK DETAILS 4214825/C 02/2019 NOTES: (continued) 6. Publication IPC-7351 may have alternate designs. 7. Solder mask tolerances between and around signal pads can vary based on board fabrication site. www.ti.com EXAMPLE STENCIL DESIGN D0008A SOIC - 1.75 mm max height SMALL OUTLINE INTEGRATED CIRCUIT 8X (.061 ) [1.55] SYMM 1 8 8X (.024) [0.6] 6X (.050 ) [1.27] SYMM 5 4 (R.002 ) TYP [0.05] (.213) [5.4] SOLDER PASTE EXAMPLE BASED ON .005 INCH [0.125 MM] THICK STENCIL SCALE:8X 4214825/C 02/2019 NOTES: (continued) 8. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate design recommendations. 9. Board assembly site may have different recommendations for stencil design. www.ti.com MECHANICAL DATA NHN0016A LDA16A (REV A) www.ti.com IMPORTANT NOTICE AND DISCLAIMER TI PROVIDES TECHNICAL AND RELIABILITY DATA (INCLUDING DATASHEETS), DESIGN RESOURCES (INCLUDING REFERENCE DESIGNS), APPLICATION OR OTHER DESIGN ADVICE, WEB TOOLS, SAFETY INFORMATION, AND OTHER RESOURCES "AS IS" AND WITH ALL FAULTS, AND DISCLAIMS ALL WARRANTIES, EXPRESS AND IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRD PARTY INTELLECTUAL PROPERTY RIGHTS. These resources are intended for skilled developers designing with TI products. You are solely responsible for (1) selecting the appropriate TI products for your application, (2) designing, validating and testing your application, and (3) ensuring your application meets applicable standards, and any other safety, security, or other requirements. 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