Product Folder Sample & Buy Technical Documents Support & Community Tools & Software LM2672 SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 LM2672 SIMPLE SWITCHER® Power Converter High Efficiency 1-A Step-Down Voltage Regulator with Features 1 Features 3 Description • • • • • The LM2672 series of regulators are monolithic integrated DC-DC converter built with a LMDMOS process. These regulators provide all the active functions for a step-down (buck) switching regulator, capable of driving a 1-A 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 and PDIP Packages Requires only 5 External Components 3.3-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 Specified 1-A Output Load Current Wide Input Voltage Range: 8 V to 40 V 260-kHz Fixed Frequency Internal Oscillator TTL Shutdown Capability, Low Power Standby Mode Soft-Start and Frequency Synchronization Thermal Shutdown and Current Limit Protection 2 Applications • • Simple High Efficiency (>90%) Step-Down (Buck) Regulator Efficient Preregulator for Linear Regulators Requiring a minimum number of external components, these regulators are simple to use and include patented internal frequency compensation, fixed frequency oscillator, external shutdown, softstart, and frequency synchronization. The LM2672 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. Device Information(1) PART NUMBER LM2672 PACKAGE BODY SIZE (NOM) SOIC (8) 5.00 mm × 6.20 mm PDIP (8) 10.16 mm × 6.60 mm WSON (16) 5.00 mm × 5.00 mm (1) For all available packages, see the orderable addendum at the end of the data sheet. Typical Application Copyright © 2016, Texas Instruments Incorporated Fixed output voltage versions 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. LM2672 SNVS136L – 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 7.9 4 4 4 4 5 5 5 6 Absolute Maximum Ratings ...................................... ESD Ratings.............................................................. Recommended Operating Conditions....................... Thermal Information .................................................. Electrical Characteristics – 3.3 V .............................. Electrical Characteristics – 5 V ................................. Electrical Characteristics – 12 V ............................... Electrical Characteristics – Adjustable...................... Electrical Characteristics – All Output Voltage Versions ..................................................................... 7.10 Typical Characteristics ............................................ 7.11 Typical Characteristics – Fixed Output Voltage Versions ..................................................................... 8 9 6 7 9 Parameter Measurement Information ................ 10 Detailed Description ............................................ 11 9.1 9.2 9.3 9.4 Overview ................................................................. Functional Block Diagram ....................................... Feature Description................................................. Device Functional Modes........................................ 11 11 11 12 10 Application and Implementation........................ 13 10.1 Application Information.......................................... 13 10.2 Typical Applications .............................................. 14 11 Power Supply Recommendations ..................... 25 12 Layout................................................................... 25 12.1 Layout Guidelines ................................................. 25 12.2 Layout Examples................................................... 25 13 Device and Documentation Support ................. 27 13.1 13.2 13.3 13.4 13.5 13.6 Documentation Support ........................................ Receiving Notification of Documentation Updates Community Resources.......................................... Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 27 27 27 27 27 27 14 Mechanical, Packaging, and Orderable Information ........................................................... 27 14.1 DAP (WSON Package) ......................................... 27 4 Revision History NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision K (April 2013) to Revision L 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 J (April 2013) to Revision K • 2 Page Changed layout of National Data Sheet to TI format ............................................................................................................. 1 Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 LM2672 www.ti.com SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 5 Description (continued) A family of standard inductors for use with the LM2672 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 ±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 μA 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 NHN Package 16-Pin WSON Top View CB 1 8 VSW CB 1 16 VSW SS 2 7 VIN NC 2 15 VSW SYNC 3 6 GND NC 3 14 VIN SS 4 13 NC FB 4 5 ON/OFF Not to scale DAP NC 5 12 GND SYNC 6 11 GND NC 7 10 NC FB 8 9 ON/OFF Not to scale Pin Functions PIN NAME I/O DESCRIPTION SOIC, PDIP WSON CB 1 1 I Boot-strap capacitor connection for high-side driver. Connect a high quality 100-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. 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. NC — 2, 3, 5, 7, 10, 13 — No connection pins. 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. SS 2 4 I Soft-start capacitor pin. Connect a capacitor from this pin to GND to control the output voltage ramp. If the feature not desired, the pin can be left floating. SYNC 3 6 I This input allows control of the switching clock frequency. If left open-circuited the regulator is switched at the internal oscillator frequency, typically 260 kHz. VIN 7 14 I 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. 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. Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 3 LM2672 SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 www.ti.com 7 Specifications 7.1 Absolute Maximum Ratings over recommended operating junction temperature range of –40°C to 125°C (unless otherwise noted) (1) MIN Supply voltage ON/OFF pin voltage, VSH –0.1 UNIT 45 V 6 V –1 V VSW + 8 V 14 V Switch voltage to ground Boost pin voltage MAX Feedback pin voltage, VFB –0.3 Power dissipation Internally limited D package Lead temperature Vapor phase (60s) 215 Infrared (15s) 220 P package (soldering, 10s) Maximum junction temperature, TJ Storage temperature, Tstg (1) °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. 7.2 ESD Ratings V(ESD) (1) Electrostatic discharge VALUE UNIT ±2000 V MAX UNIT Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. 7.3 Recommended Operating Conditions over operating free-air temperature range (unless otherwise noted) MIN TJ Supply voltage 6.5 40 V Operating junction temperature –40 125 °C 7.4 Thermal Information LM2672 THERMAL METRIC (1) (2) D (SOIC) P (PDIP) WSON (NHN) 8 PINS 8 PINS 16 PINS UNIT RθJA Junction-to-ambient thermal resistance 105 95 — °C/W RθJC(top) Junction-to-case (top) thermal resistance — — — °C/W RθJB Junction-to-board thermal resistance — — — °C/W ψJT Junction-to-top characterization parameter — — — °C/W ψJB Junction-to-board characterization parameter — — — °C/W RθJC(bot) Junction-to-case (bottom) thermal resistance — — — °C/W (1) (2) 4 For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report. Thermal resistances were simulated on 4-layer JEDEC board. Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 LM2672 www.ti.com SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 7.5 Electrical Characteristics – 3.3 V TJ = 25°C (unless otherwise noted; see Figure 19) (1) PARAMETER VIN = 8 V to 40 V, ILOAD = 20 mA to 1 A VOUT Output voltage Efficiency (1) (2) (3) TYP (3) TJ = 25°C 3.251 3.3 TJ = –40°C to 125°C 3.201 TJ = 25°C VIN = 6.5 V to 40 V, ILOAD = 20 mA to 500 mA η MIN (2) TEST CONDITIONS TJ = –40°C to 125°C 3.35 3.3 UNIT 3.35 3.399 3.201 VIN = 12 V, ILOAD = 1 A MAX (2) 3.35 V 3.399 86% External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator performance. When the LM2672 is used as shown in Figure 19 test circuits, system performance is as specified by the system parameters section of Electrical Characteristics. All limits specified at room temperature and at temperature extremes. All room temperature limits are 100% production tested. All limits at temperature extremes are specified through correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). Typical numbers are at 25°C and represent the most likely norm. 7.6 Electrical Characteristics – 5 V TJ = 25°C (unless otherwise noted; see Figure 19) (1) PARAMETER TEST CONDITIONS VIN = 8 V to 40 V, ILOAD = 20 mA to 1 A VOUT Output voltage Efficiency (1) (2) (3) TJ = –40°C to 125°C TJ = 25°C VIN = 6.5 V to 40 V, ILOAD = 20 mA to 500 mA η TJ = 25°C TJ = –40°C to 125°C MIN (2) TYP (3) 4.925 5 5.075 5 5.075 4.85 4.925 5.15 4.85 VIN = 12 V, ILOAD = 1 A MAX (2) UNIT V 5.15 90% External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator performance. When the LM2672 is used as shown in Figure 19 test circuits, system performance is as specified by the system parameters section of Electrical Characteristics. All limits specified at room temperature and at temperature extremes. All room temperature limits are 100% production tested. All limits at temperature extremes are specified through correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). Typical numbers are at 25°C and represent the most likely norm. 7.7 Electrical Characteristics – 12 V TJ = 25°C (unless otherwise noted; see Figure 19) (1) PARAMETER VOUT Output voltage VIN = 15 V to 40 V, ILOAD = 20 mA to 1 A η Efficiency VIN = 24 V, ILOAD = 1 A (1) (2) (3) MIN (2) TYP (3) TJ = 25°C 11.82 12 TJ = –40°C to 125°C 11.64 TEST CONDITIONS MAX (2) UNIT 12.18 12.36 V 94% External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator performance. When the LM2672 is used as shown in Figure 19 test circuits, system performance is as specified by the system parameters section of Electrical Characteristics. All limits specified at room temperature and at temperature extremes. All room temperature limits are 100% production tested. All limits at temperature extremes are specified through correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). Typical numbers are at 25°C and represent the most likely norm. Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 5 LM2672 SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 www.ti.com 7.8 Electrical Characteristics – Adjustable TJ = 25°C (unless otherwise noted; see Figure 19) (1) TEST CONDITIONS MIN (2) TYP (3) VIN = 8 V to 40 V, ILOAD = 20 mA to 1 A, TJ = 25°C VOUT programmed for 5 V (see TJ = –40°C to 125°C Figure 19) 1.192 1.21 VIN = 6.5 V to 40 V, ILOAD = 20 mA to TJ = 25°C 500 mA, VOUT programmed for 5 V (see TJ = –40°C to 125°C Figure 19) 1.192 PARAMETER VFB Feedback voltage Efficiency η (1) (2) (3) MAX (2) UNIT 1.228 1.174 1.246 1.21 1.228 1.174 V 1.246 VIN = 12 V, ILOAD = 1 A 90% External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator performance. When the LM2672 is used as shown in Figure 19 test circuits, system performance is as specified by the system parameters section of Electrical Characteristics. All limits specified at room temperature and at temperature extremes. All room temperature limits are 100% production tested. All limits at temperature extremes are specified through correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). Typical numbers are at 25°C and represent the most likely norm. 7.9 Electrical Characteristics – All Output Voltage Versions TJ = 25°C, VIN = 12 V for the 3.3 V, 5 V, and Adjustable versions and VIN = 24V for the 12V version, and ILOAD = 100 mA (unless otherwise noted) PARAMETER IQ Quiescent current MIN (1) TYP (2) TEST CONDITIONS VFEEDBACK = 8 V for 3.3 V, 5 V, and adjustable versions 2.5 VFEEDBACK = 15 V for 12 V versions 2.5 50 Standby quiescent current ICL Current limit IL Output leakage current RDS(ON) Switch on-resistance ISWITCH = 1 A fO Oscillator frequency Measured at switch pin D Maximum duty cycle TJ = 25°C Minimum duty cycle TJ = –40°C to 125°C Feedback bias current VFEEDBACK = 1.3 V, adjustable version only 85 TJ = 25°C 1.4 IBIAS ON/OFF Pin = 0 V TJ = 25°C ISTBY TJ = –40°C to 125°C MAX (1) UNIT 3.6 100 150 1.25 1.55 1.2 2.1 2.2 mA μA A VSWITCH = 0 V, ON/OFF Pin = 0 V, VIN = 40 V 1 25 μA VSWITCH = −1 V, ON/OFF Pin = 0 V 6 15 mA 0.25 0.3 TJ = 25°C TJ = –40°C to 125°C 0.5 TJ = 25°C TJ = –40°C to 125°C 260 225 275 Ω kHz 95% 0% nA VS/D ON/OFF pin voltage IS/D ON/OFF pin current ON/OFF Pin = 0 V FSYNC Synchronization frequency VSYNC = 3.5 V, 50% duty cycle 400 kHz VSYNC Synchronization threshold voltage 1.4 V TJ = 25°C 0.63 VSS Soft-start voltage ISS Soft-start current (1) (2) 6 TJ = –40°C to 125°C 0.8 TJ = 25°C TJ = –40°C to 125°C TJ = –40°C to 125°C 20 7 37 0.53 TJ = 25°C TJ = –40°C to 125°C 2 0.73 4.5 1.5 6.9 V μA V μA All limits specified at room temperature and at temperature extremes. All room temperature limits are 100% production tested. All limits at temperature extremes are specified through correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). Typical numbers are at 25°C and represent the most likely norm. Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 LM2672 www.ti.com SNVS136L – 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 © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 7 LM2672 SNVS136L – 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 © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 LM2672 www.ti.com SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 Typical Characteristics (continued) Figure 13. Dropout Voltage, 3.3-V Option Figure 14. Dropout Voltage, 5-V Option 7.11 Typical Characteristics – Fixed Output Voltage Versions see Figure 19 VSW pin voltage, 10 V/div Inductor current, 0.5 A/div Output ripple voltage, 20 mV/div AC-coupled VIN = 20 V, VOUT = 5 V, ILOAD = 1 A, L = 47 μH, COUT = 68 μF, COUTESR = 50 mΩ Figure 15. Continuous Mode Switching Waveforms, Horizontal Time Base: 1 μs/div Output voltage, 100 mV/div, AC-coupled Load current: 200 mA to 1 A load pulse VIN = 20 V, VOUT = 5 V, ILOAD = 1 A, L = 47 μH, COUT = 68 μF, COUTESR = 50 mΩ Figure 17. Load Transient Response for Continuous Mode, Horizontal Time Base: 50 μs/div VSW pin voltage, 10 V/div Inductor current, 0.5 A/div Output ripple voltage, 20 mV/div AC-coupled VIN = 20 V, VOUT = 5 V, ILOAD = 300 mA, L = 15 μH, COUT = 68 μF (2×), COUTESR = 25 mΩ Figure 16. Discontinuous Mode Switching Waveforms, Horizontal Time Base: 1 μs/div Output voltage, 100 mV/div, AC-coupled Load current: 100 mA to 300 mA load pulse VIN = 20 V, VOUT = 5 V, L = 47 μH, COUT = 68 μF, COUTESR = 50 mΩ Figure 18. Load Transient Response for Discontinuous Mode, Horizontal Time Base: 200 μs/div Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 9 LM2672 SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 www.ti.com 8 Parameter Measurement Information Copyright © 2016, Texas Instruments Incorporated CIN = 22-μF, 50-V Tantalum Sprague 199D Series COUT = 47-μF, 25-V Tantalum Sprague 595D Series D1 = 3.3-A, 50-V Schottky Rectifier, IR 30WQ05F L1 = 68-μH Sumida #RCR110D-680L CB = 0.01-μF, 50-V ceramic Figure 19. Standard Test Circuits and Layout Guides, Fixed Output Voltage Versions 10 Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 LM2672 www.ti.com SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 9 Detailed Description 9.1 Overview The LM2672 provides all of the active functions required for a step-down (buck) switching regulator. The internal power switch is a DMOS power MOSFET to provide power supply designs with high current capability, up to 1 A, and highly efficient operation. The LM2672 is part of the SIMPLE SWITCHER® family of power converters. A complete design uses a minimum number of external components, which have been pre-determined from a variety of manufacturers. Using either this data sheet or TI's WEBENCH® design tool, a complete switching power supply can be designed quickly. Refer to LM2670 SIMPLE SWITCHER® High Efficiency 3A Step-Down Voltage Regulator with Sync for additional application information. 9.2 Functional Block Diagram Copyright © 2016, Texas Instruments Incorporated 9.3 Feature Description 9.3.1 Switch Output This is the output of a power MOSFET switch connected directly to the input voltage. The switch provides energy to an inductor, an output capacitor and the load circuitry under control of an internal pulse-width-modulator (PWM). The PWM controller is internally clocked by a fixed 260-kHz oscillator. In a standard step-down application the duty cycle (time ON or time OFF) of the power switch is proportional to the ratio of the power supply output voltage to the input voltage. The voltage on the VSW pin cycles between Vin (switch ON) and below ground by the voltage drop of the external Schottky diode (switch OFF). Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 11 LM2672 SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 www.ti.com Feature Description (continued) 9.3.2 C Boost A capacitor must be connected from the CB pin to the VSW pin. This capacitor boosts the gate drive to the internal MOSFET above Vin to fully turn it ON. This minimizes conduction losses in the power switch to maintain high efficiency. The recommended value for C Boost is 0.01 μF. 9.3.3 SYNC This input allows control of the switching clock frequency. If left open-circuited the regulator is switched at the internal oscillator frequency, typically 260 kHz. An external clock can be used to force the switching frequency and thereby control the output ripple frequency of the regulator. This capability provides for consistent filtering of the output ripple from system to system as well as precise frequency spectrum positioning of the ripple frequency which is often desired in communications and radio applications. This external frequency must be greater than the LM2672 internal oscillator frequency, which could be as high as 275 kHz, to prevent an erroneous reset of the internal ramp oscillator and PWM control of the power switch. The ramp oscillator is reset on the positive going edge of the sync input signal. TI recommends that the external TTL or CMOS compatible clock (between 0 V and a level greater than 3 V) be AC-coupled to the SYNC pin through a 100-pF capacitor and a 1-kΩ resistor to ground. When the SYNC function is used, current limit frequency foldback is not active. Therefore, the device may not be fully protected against extreme output short circuit conditions. 9.3.4 Feedback This is the input to a two-stage high gain amplifier, which drives the PWM controller. Connect the FB pin directly to the output for proper regulation. For the fixed output devices (3.3-V, 5-V, and 12-V outputs), a direct wire connection to the output is all that is required as internal gain setting resistors are provided inside the LM2672. For the adjustable output version two external resistors are required to set the DC output voltage. For stable operation of the power supply, it is important to prevent coupling of any inductor flux to the feedback input. 9.4 Device Functional Modes 9.4.1 ON/OFF This input provides an electrical ON/OFF control of the power supply. Connecting this pin to ground or to any voltage less than 1.4 V completely turns OFF the regulator. The current drain from the input supply when OFF is only 50 μA. The ON/OFF input has an internal pullup current source of approximately 20 μA and a protection clamp Zener diode of 7 V to ground. When electrically driving the ON/OFF pin the high voltage level for the ON condition must not exceed the 6-V absolute maximum limit. When ON/OFF control is not required this pin must be left open. 9.4.2 Shutdown Mode The ON/OFF pin provides electrical ON and OFF control for the LM2671. When the voltage of this pin is lower than 1.4 V, the device is shutdown mode. The typical standby current in this mode is 50 μA. 9.4.3 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. 12 Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 LM2672 www.ti.com SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 10 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. 10.1 Application Information The LM2672 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 1 A. The following design procedure can be used to select components for the LM2672. 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 (½ 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 µF, L = 22 µH. Note that 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 short-circuit 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 shortcircuit condition. Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 13 LM2672 SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 www.ti.com 10.2 Typical Applications 10.2.1 Typical Application for Fixed Output Voltage Versions Copyright © 2016, Texas Instruments Incorporated CIN = 22-μF, 50-V Tantalum, Sprague 199D Series COUT = 47-μF, 25-V Tantalum, Sprague 595D Series D1 = 3.3-A, 50-V Schottky Rectifier, IR 30WQ05F L1 = 68-μH Sumida #RCR110D-680L CB = 0.01-μF, 50-V Ceramic Figure 20. Fixed Output Voltage Typical Application 10.2.1.1 Design Requirements Table 1 lists the design requirements for the fixed output voltage application. Table 1. Fixed Output Voltage Application 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) 1A 10.2.1.2 Detailed Design Procedure 10.2.1.2.1 Inductor Selection (L1) First, select the correct inductor value selection guide from Figure 23, Figure 24, or Figure 25 (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 24. 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 24, the inductance region intersected by the 12 V horizontal line and the 1 A vertical line is 33 μH, and the inductor code is L23. Select an appropriate inductor from the four manufacturer's part numbers listed in Table 2. Each manufacturer makes a different style of inductor to allow flexibility in meeting various design requirements. The inductance value required is 33 μH. From Table 2, go to the L23 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. 14 Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 LM2672 www.ti.com SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 Table 2. Inductor Manufacturers' Part Numbers IND. REF. DESG. INDUCTANCE (μH) CURRENT (A) L4 68 L5 47 L6 SCHOTT RENCO PULSE ENGINEERING COILCRAFT THROUGH HOLE SURFACE MOUNT THROUGH HOLE SURFACE MOUNT THROUGH HOLE SURFACE MOUNT SURFACE MOUNT 0.32 67143940 67144310 RL-1284-68-43 RL1500-68 PE-53804 PE-53804-S DO1608-683 0.37 67148310 67148420 RL-1284-47-43 RL1500-47 PE-53805 PE-53805-S DO1608-473 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 0.70 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-53821 PE-53821-S DO3316-683 L22 47 1.17 67144080 67144460 RL-5471-6 — PE-53822 PE-53822-S DO3316-473 L23 33 1.4 67144090 67144470 RL-5471-7 — PE-53823 PE-53823-S DO3316-333 L24 22 1.7 67148370 67148480 RL-1283-22-43 — PE-53824 PE-53824-S DO3316-223 L27 220 1 67144110 67144490 RL-5471-2 — PE-53827 PE-53827-S DO5022P-224 L28 150 1.2 67144120 67144500 RL-5471-3 — PE-53828 PE-53828-S DO5022P-154 L29 100 1.47 67144130 67144510 RL-5471-4 — PE-53829 PE-53829-S DO5022P-104 L30 68 1.78 67144140 67144520 RL-5471-5 — PE-53830 PE-53830-S DO5022P-683 10.2.1.2.2 Output Capacitor Selection (COUT) Select an output capacitor from the output capacitor table in Table 3. 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 Table 3. Choose a capacitor value and voltage rating from the line that contains the inductance value of 33 μH. The capacitance and voltage rating values corresponding to the 33 μH. The capacitor list contains through-hole electrolytic capacitors from four different capacitor manufacturers and surface mount tantalum capacitors from two different capacitor manufacturers. Surface mount: • 68-μF, 10-V Sprague 594D series • 100-μF, 10-V AVX TPS series Through hole: • 68-μF, 10-V Sanyo OS-CON SA series • 220-μF, 35-V Sanyo MV-GX series • 220-μF, 35-V Nichicon PL series • 220-μF, 35-V Panasonic HFQ series Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 15 LM2672 SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 www.ti.com Table 3. Output Capacitor Table OUTPUT CAPACITOR OUTPUT VOLTAGE (V) 3.3 5 12 INDUCTANCE (μH) SURFACE MOUNT THROUGH HOLE SPRAGUE 594D SERIES (μF/V) AVX TPS SERIES (μF/V) SANYO OS-CON SA SERIES (μF/V) SANYO MV-GX SERIES (μF/V) NICHICON PL SERIES (μF/V) PANASONIC HFQ SERIES (μF/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 (2×) 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 10.2.1.2.3 Catch Diode Selection (D1) 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 LM2672. The most stressful condition for this diode is a shorted output condition. Refer to the table shown in Table 4. 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. The reverse voltage rating of the diode must be at least 1.25 times the maximum input voltage. 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 LM2672 using short leads and short printed circuit traces. 16 Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 LM2672 www.ti.com SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 Table 4. Schottky Diode Selection Table VR 20 V 30 V 40 V 50 V 1-A DIODES 3-A DIODES SURFACE MOUNT THROUGH HOLE SURFACE MOUNT THROUGH HOLE SK12 1N5817 SK32 1N5820 B120 SR102 — SR302 SK13 1N5818 SK33 1N5821 B130 11DQ03 30WQ03F 31DQ03 MBRS130 SR103 — — SK14 1N5819 SK34 1N5822 B140 11DQ04 30BQ040 MBR340 MBRS140 SR104 30WQ04F 31DQ04 10BQ040 — MBRS340 SR304 10MQ040 — MBRD340 — 15MQ040 — — — SK15 MBR150 SK35 MBR350 B150 11DQ05 30WQ05F 31DQ05 10BQ050 SR105 — SR305 10.2.1.2.4 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 ½ the DC load current. The capacitor manufacturer data sheet must be checked to assure that this current rating is not exceeded. Figure 21 shows 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 21. 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. The tables in Table 5 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. Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 17 LM2672 SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 www.ti.com Table 5. Recommended Application Voltage for AVX TPS and Sprague 594D Tantalum Chip Capacitors Derated for 85°C RECOMMENDED APPLICATION VOLTAGE VOLTAGE RATING 3.3 6.3 5 10 10 20 12 25 15 35 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 12 V, an aluminum electrolytic capacitor with a voltage rating greater than 15 V (1.25 × 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 ½ the DC load current. In this example, with a 1-A load, a capacitor with a RMS current rating of at least 500 mA is required. The curves shown in Figure 21 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 500 mA. For a through hole design, a 330-μF, 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 5, and the Sprague 594D series data sheet, a Sprague 594D 15-μF, 25-V capacitor is adequate. 10.2.1.2.5 Boost Capacitor (CB) This capacitor develops the necessary voltage to turn the switch gate on fully. All applications must use a 0.01μF, 50-V ceramic capacitor. 10.2.1.2.6 Soft-Start Capacitor (CSS, Optional) This capacitor controls the rate at which the device starts up. The formula for the soft-start capacitor CSS is calculated with Equation 1. where • • • • • • ISS = Soft-start current (4.5 µA, typical) tSS = Soft-start time (selected) VSSTH = Soft-start threshold voltage (0.63 V, typical) VOUT = Output voltage (selected) VSCHOTTKY = Schottky diode voltage drop (0.4 V, typical) VIN = Input voltage (selected) (1) If this feature is not desired, leave this pin open. With certain soft-start capacitor values and operating conditions, the LM2672 can exhibit an overshoot on the output voltage during turn on. Especially when starting up into no load or low load, the soft-start function may not be effective in preventing a larger voltage overshoot on the output. With larger loads or lower input voltages during startup this effect is minimized. In particular, avoid using soft-start capacitors between 0.033 µF and 1 µF. For this application, selecting a start-up time of 10 ms and using the formula for CSS results in a value of Equation 2. (2) 18 Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 LM2672 www.ti.com SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 10.2.1.2.7 Frequency Synchronization (Optional) The LM2672 (oscillator) can be synchronized to run with an external oscillator, using the sync pin (pin 3). By doing so, the LM2672 can be operated at higher frequencies than the standard frequency of 260 kHz. This allows for a reduction in the size of the inductor and output capacitor. As shown in Figure 22, a signal applied to a RC filter at the sync pin causes the device to synchronize to the frequency of that signal. For a signal with a peak-to-peak amplitude of 3 V or greater, a 1-kΩ resistor and a 100pF capacitor are suitable values. For all applications, use a 1-kΩ resistor and a 100-pF capacitor for the RC filter. Figure 22. Synchronization on LM2672 10.2.1.3 Application Curves Figure 23. LM2672, 3.3-V Output Figure 24. LM2672, 5-V Output Figure 25. LM2672, 12-V Output Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 19 LM2672 SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 www.ti.com 10.2.2 Typical Application for Adjustable Output Voltage Versions Copyright © 2016, Texas Instruments Incorporated CIN = 22-μF, 50-V Tantalum, Sprague 199D Series COUT = 47-μF, 25-V Tantalum, Sprague 595D Series D1 = 3.3-A, 50-V Schottky Rectifier, IR 30WQ05F L1 = 68-μH Sumida #RCR110D-680L R1 = 1.5-kΩ , 1% CB = 0.01-μF, 50-V Ceramic Figure 26. Adjustable Output Voltage Typical Application 10.2.2.1 Design Requirements Table 6 lists the design requirements for the adjustable output voltage application. Table 6. Adjustable Output Voltage Application Parameters PARAMETERS VALUE Regulated output voltage, VOUT 20 V Maximum input voltage, VIN(max) 28 V Maximum load current, ILOAD(max) 1A Switching frequency, F Fixed at a nominal 260 kHz 10.2.2.2 Detailed Design Procedure 10.2.2.2.1 Programming Output Voltage For this application, TI recommends selecting R1 and R2, as shown in Parameter Measurement Information. Use Equation 3 to select the appropriate resistor values. where • VREF = 1.21 V (3) Select a value for R1 between 240 Ω and 1.5 kΩ. 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 as in Equation 4. (4) 20 Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 LM2672 www.ti.com SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 For this application example, select R1 to be 1 kΩ, 1%. Solve for R2 with Equation 5. (5) R2 = 1 kΩ (16.53 − 1) = 15.53 kΩ, closest 1% value is 15.4 kΩ. R2 = 15.4 kΩ. 10.2.2.2.2 Inductor Selection (L1) Calculate the inductor Volt × microsecond constant E × T (V × μs) with Equation 6. where • • VSAT = internal switch saturation voltage = 0.25 V VD = diode forward voltage drop = 0.5 V (6) For this application example, calculate the inductor Volt × microsecond constant (E × T) with Equation 7. (7) 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 in Figure 27. E × T = 21.6 (V × μs). On the horizontal axis, select the maximum load current (ILOAD(max) = 1 A). 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 × μs) horizontal line and the 1-A vertical line is 68 μH, and the inductor code is L30. Select an appropriate inductor from the four manufacturer's part numbers listed in Table 2. For information on the different types of inductors, see the inductor selection in the fixed output voltage design procedure. From the table in Table 2, locate line L30, and select an inductor part number from the list of manufacturers' part numbers. 10.2.2.2.3 Output Capacitor SeIection (COUT) Select an output capacitor from the capacitor code selection guide in Table 7. 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 7. For this example, use the 15 to 20 V row. The capacitor code corresponding to an inductance of 68 μH is C20. Table 7. Capacitor Code Selection Guide INDUCTANCE (μH) CASE STYLE (1) OUTPUT VOLTAGE (V) 22 33 47 SM and TH 1.21 to 2.5 — — SM and TH 2.5 to 3.75 — — SM and TH 3.75 to 5 — SM and TH 5 to 6.25 — SM and TH 6.25 to 7.5 C8 C4 C7 C6 C6 C6 C6 SM and TH 7.5 to 10 C9 C10 C11 C12 C13 C13 C13 SM and TH 10 to 12.5 C14 C11 C12 C12 C13 C13 C13 SM and TH 12.5 to 15 C15 C16 C17 C17 C17 C17 C17 SM and TH 15 to 20 C18 C19 C20 C20 C20 C20 C20 SM and TH 20 to 30 C21 C22 C22 C22 C22 C22 C22 TH 30 to 37 C23 C24 C24 C25 C25 C25 C25 (1) 68 100 150 220 — — C1 C2 C3 — C1 C2 C3 C3 — C4 C5 C6 C6 C6 C4 C7 C6 C6 C6 C6 SM = surface mount, TH = through hole Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 21 LM2672 SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 www.ti.com Select an appropriate capacitor value and voltage rating, using the capacitor code, from the output capacitor selection table in Table 8. 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 table in Table 8, choose a capacitor value (and voltage rating) that intersects the capacitor code(s) selected in section A, C20 (Table 8). The capacitance and voltage rating values corresponding to the capacitor code C20 are surface mount and through hole. Surface mount: • 33-μF, 25-V Sprague 594d series • 33-μF, 25-V AVX TPS series Through hole: • 33-μF, 25-V Sanyo OS-CON SC series • 120-μF, 35-V Sanyo MV-GX series • 120-μF, 35-V Nichicon PL series • 120-μF, 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. Output Capacitor Selection Table OUTPUT CAPACITOR SURFACE MOUNT THROUGH HOLE CAP. REF. DESG. # SPRAGUE 594D SERIES (μF/V) AVX TPS SERIES (μF/V) SANYO OS-CON SA SERIES (μF/V) SANYO MV-GX SERIES (μF/V) NICHICON PL SERIES (μF/V) PANASONIC HFQ SERIES (μF/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 (2×) 33/25 47/25 (1) 220/35 220/35 220/35 C19 33/25 33/25 33/25 (1) 150/35 150/35 150/35 C20 33/25 33/25 33/25 (1) 120/35 120/35 120/35 (2) (1) (2) 22 C21 33/35 (2×) 22/25 150/35 150/35 150/35 C22 33/35 22/35 See See (2) 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 See (2) See (2) See (2) 150/50 82/50 82/50 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. Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 LM2672 www.ti.com SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 10.2.2.2.4 Catch Diode Selection (D1) 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 LM2672. The most stressful condition for this diode is a shorted output condition. Refer to the table shown in Table 4. Schottky diodes provide the best performance, and in this example a 1-A, 40-V Schottky diode would be a good choice. If the circuit must withstand a continuous shorted output, a higher current (at least 2.2-A) Schottky diode is recommended. The reverse voltage rating of the diode must be at least 1.25 times the maximum input voltage. 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 LM2672 using short leads and short printed circuit traces. 10.2.2.2.5 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 ½ the DC load current. The capacitor manufacturer data sheet must be checked to assure that this current rating is not exceeded. Figure 21 shows 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 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. The tables in Table 5 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 28 V, an aluminum electrolytic capacitor with a voltage rating of at least 35 V (1.25 × VIN) is required. The RMS current rating requirement for the input capacitor in a buck regulator is approximately ½ the DC load current. In this example, with a 1-A load, a capacitor with a RMS current rating of at least 500 mA is required. The curves shown in Figure 21 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 500 mA. For a through hole design, a 330-μF, 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 Table 5, and the Sprague 594D series datasheet, a Sprague 594D 15-μF, 50-V capacitor is adequate. 10.2.2.2.6 Boost Capacitor (CB) This capacitor develops the necessary voltage to turn the switch gate on fully. All applications must use a 0.01-μF, 50-V ceramic capacitor. If the soft-start and frequency synchronization features are desired, see steps 6 and 7 in the fixed output design procedure. Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 23 LM2672 SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 www.ti.com 10.2.2.3 Application Curve Figure 27. LM2672, Adjustable Output 24 Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 LM2672 www.ti.com SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 11 Power Supply Recommendations The input voltage for the power supply is connected to the VIN pin. In addition to providing energy to the load the input voltage also provides bias for the internal circuitry of the LM2672. For ensured performance, the input voltage must be in the range of 6.5 V to 40 V. For best performance of the power supply, the VIN pin must always be bypassed with an input capacitor placed close to this pin and GND. 12 Layout 12.1 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 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. This is the ground reference connection for all components in the power supply. In fast-switching, high-current applications such as those implemented with the LM2672, TI recommends that a broad ground plane be used to minimize signal coupling throughout the circuit. 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. 12.1.1 WSON Package Devices The LM2672 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) can and must be connected to PCB Ground plane/island. For CAD and assembly guidelines, refer to AN-1187 Leadless Leadframe Package (LLP). 12.2 Layout Examples CIN = 15-μF, 50-V, solid tantalum Sprague 594D series COUT = 68-μF, 16-V, solid tantalum Sprague 594D series D1 = 1-A, 40-V Schottky rectifier, surface mount L1 = 33-μH, L23, coilcraft DO3316 CB = 0.01-μF, 50-V ceramic Figure 28. Typical Surface Mount PC Board Layout, Fixed Output Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 25 LM2672 SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 www.ti.com Layout Examples (continued) CIN = 15-μF, 50-V, solid tantalum Sprague 594D series COUT = 33-μF, 25-V, solid tantalum Sprague 594D series D1 = 1-A, 40-V Schottky rectifier, surface mount L1 = 68-μH, L30, coilcraft DO3316 CB = 0.01-μF, 50-V ceramic R1 = 1k, 1%, R2: use formula in Detailed Design Procedure Figure 29. Typical Surface Mount PC Board Layout, Adjustable Output 26 Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 LM2672 www.ti.com SNVS136L – SEPTEMBER 1998 – REVISED JUNE 2016 13 Device and Documentation Support 13.1 Documentation Support 13.1.1 Related Documentation For related documentation see the following: • LM2670 SIMPLE SWITCHER® High Efficiency 3A Step-Down Voltage Regulator with Sync (SNVS036) • AN-1187 Leadless Leadframe Package (LLP) (SNOA401) 13.2 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. 13.3 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 E2E™ 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. 13.4 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. 13.5 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. 13.6 Glossary SLYZ022 — TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 14 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. 14.1 DAP (WSON Package) The die attach pad (DAP) must be connected to the PCB ground plane. For CAD and assembly guidelines, refer to AN-1187 Leadless Leadframe Package (LLP). Submit Documentation Feedback Copyright © 1998–2016, Texas Instruments Incorporated Product Folder Links: LM2672 27 PACKAGE OPTION ADDENDUM www.ti.com 10-Feb-2016 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (°C) Device Marking (4/5) LM2672LD-ADJ/NOPB ACTIVE WSON NHN 16 1000 Green (RoHS & no Sb/Br) CU SN Level-3-260C-168 HR -40 to 125 S0004B LM2672M-12 NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2672 M-12 LM2672M-12/NOPB ACTIVE SOIC D 8 95 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 2672 M-12 LM2672M-3.3 NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2672 M3.3 LM2672M-3.3/NOPB ACTIVE SOIC D 8 95 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 2672 M3.3 LM2672M-5.0 NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2672 M5.0 LM2672M-5.0/NOPB ACTIVE SOIC D 8 95 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 2672 M5.0 LM2672M-ADJ NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2672 MADJ LM2672M-ADJ/NOPB ACTIVE SOIC D 8 95 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 2672 MADJ LM2672MX-12/NOPB ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 2672 M-12 LM2672MX-3.3/NOPB ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 2672 M3.3 LM2672MX-5.0 NRND SOIC D 8 2500 TBD Call TI Call TI -40 to 125 2672 M5.0 LM2672MX-5.0/NOPB ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 2672 M5.0 LM2672MX-ADJ NRND SOIC D 8 2500 TBD Call TI Call TI -40 to 125 2672 MADJ LM2672MX-ADJ/NOPB ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 2672 MADJ LM2672N-12/NOPB ACTIVE PDIP P 8 40 Green (RoHS & no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2672 N-12 LM2672N-3.3/NOPB ACTIVE PDIP P 8 40 Green (RoHS & no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2672 N-3.3 Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com Orderable Device 10-Feb-2016 Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (°C) Device Marking (4/5) LM2672N-5.0/NOPB ACTIVE PDIP P 8 40 Green (RoHS & no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2672 N-5.0 LM2672N-ADJ/NOPB ACTIVE PDIP P 8 40 Green (RoHS & no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2672 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. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) 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/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish 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 Samples PACKAGE OPTION ADDENDUM www.ti.com 10-Feb-2016 Addendum-Page 3 PACKAGE MATERIALS INFORMATION www.ti.com 10-Feb-2016 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 LM2672LD-ADJ/NOPB WSON NHN 16 1000 178.0 12.4 5.3 5.3 1.3 8.0 12.0 Q1 LM2672MX-12/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM2672MX-3.3/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM2672MX-5.0 SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM2672MX-5.0/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM2672MX-ADJ SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM2672MX-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 10-Feb-2016 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM2672LD-ADJ/NOPB WSON NHN 16 1000 213.0 191.0 55.0 LM2672MX-12/NOPB SOIC D 8 2500 367.0 367.0 35.0 LM2672MX-3.3/NOPB SOIC D 8 2500 367.0 367.0 35.0 LM2672MX-5.0 SOIC D 8 2500 367.0 367.0 35.0 LM2672MX-5.0/NOPB SOIC D 8 2500 367.0 367.0 35.0 LM2672MX-ADJ SOIC D 8 2500 367.0 367.0 35.0 LM2672MX-ADJ/NOPB SOIC D 8 2500 367.0 367.0 35.0 Pack Materials-Page 2 MECHANICAL DATA NHN0016A LDA16A (REV A) www.ti.com IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. 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