LM2673 www.ti.com SNVS030N – APRIL 2000 – REVISED APRIL 2013 LM2673 SIMPLE SWITCHER® 3A Step-Down Voltage Regulator with Adjustable Current Limit Check for Samples: LM2673 FEATURES DESCRIPTION • • The LM2673 series of regulators are monolithic integrated circuits which provide all of the active functions for a step-down (buck) switching regulator capable of driving up to 3A loads with excellent line and load regulation characteristics. High efficiency (>90%) is obtained through the use of a low ONresistance DMOS power switch. The series consists of fixed output voltages of 3.3V, 5V and 12V and an adjustable output version. 1 23 • • • • • • • • Efficiency Up to 94% Simple and Easy to Design with (Using OffThe-Shelf External Components) Resistor Programmable Peak Current Limit Over a Range of 2A to 5A 150 mΩ DMOS Output Switch 3.3V, 5V and 12V Fixed Output and Adjustable (1.2V to 37V) Versions ±2% Maximum Output Tolerance Over Full Line and Load Conditions Wide Input Voltage Range: 8V to 40V 260 KHz Fixed Frequency Internal Oscillator Softstart Capability −40 to +125°C Operating Junction Temperature Range APPLICATIONS • • • Simple to Design, High Efficiency (>90%) StepDown Switching Regulators Efficient System Pre-Regulator for Linear Voltage Regulators Battery Chargers The SIMPLE SWITCHER® concept provides for a complete design using a minimum number of external components. A high fixed frequency oscillator (260KHz) allows the use of physically smaller sized components. A family of standard inductors for use with the LM2673 are available from several manufacturers to greatly simplify the design process. Other features include the ability to reduce the input surge current at power-ON by adding a softstart timing capacitor to gradually turn on the regulator. The LM2673 series also has built in thermal shutdown and resistor programmable current limit of the power MOSFET switch to protect the device and load circuitry under fault conditions. The output voltage is ensured to a ±2% tolerance. The clock frequency is controlled to within a ±11% tolerance. Typical Application Feedback 0.01 PF Input Voltage 8V to 40V CIN 2 x 15 PF/50V VIN LM2673 - 5.0 0.47 PF + + Softstart 8.2k 1 nF Current Limit Adjust Boost L Switch Ground Output 33 PH SR305 I CL = Output Voltage 5V/3A + C OUT 180 PF/16V 37,125 RADJ 1 2 3 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. SIMPLE SWITCHER, Switchers Made Simple are registered trademarks of Texas Instruments. All other trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2000–2013, Texas Instruments Incorporated LM2673 SNVS030N – APRIL 2000 – REVISED APRIL 2013 www.ti.com Connection Diagrams Figure 1. DDPAK Package (Top View) See Package Number KTW0007B Figure 2. TO-220 Package (Top View) See Package Number NDZ0007B * 1 14 VSW VIN 2 13 VSW VIN 3 12 VSW CB 4 11 * * 5 10 * 6 9 GND 7 8 CURRENT ADJ FB DAP** SOFTSTART * No Connections ** Connect to Pin 9 on PCB Figure 3. VSON-14 (Top View) See Package Number NHM0014A These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Absolute Maximum Ratings (1) (2) Input Supply Voltage 45V Softstart Pin Voltage −0.1V to 6V Switch Voltage to Ground (3) −1V to VIN Boost Pin Voltage VSW + 8V −0.3V to 14V Feedback Pin Voltage Power Dissipation Internally Limited ESD (4) 2 kV −65°C to 150°C Storage Temperature Range Soldering Temperature (1) (2) (3) (4) 2 Wave 4 sec, 260°C Infrared 10 sec, 240°C Vapor Phase 75 sec, 219°C Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings indicate conditions under which of the device is ensured. Operating Ratings do not imply ensured performance limits. For ensured performance limits and associated test condition, see the Electrical Characteristics tables. If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and specifications. The absolute maximum specification of the 'Switch Voltage to Ground' applies to DC voltage. An extended negative voltage limit of -8V applies to a pulse of up to 20 ns, -6V of 60 ns and -3V of up to 100 ns. ESD was applied using the human-body model, a 100pF capacitor discharged through a 1.5 kΩ resistor into each pin. Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 LM2673 www.ti.com SNVS030N – APRIL 2000 – REVISED APRIL 2013 Operating Ratings Supply Voltage 8V to 40V −40°C to 125°C Junction Temperature Range (TJ) Electrical Characteristics LM2673-3.3 Limits appearing in bold type face apply over the entire junction temperature range of operation, −40°C to 125°C. Specifications appearing in normal type apply for TA = TJ = 25°C. RADJ = 8.2KΩ Symbol Parameter Conditions Typ (1) Min (2) Max (2) Units 3.234/3.201 3.366/3.399 V VOUT Output Voltage VIN = 8V to 40V, 100mA ≤ IOUT ≤ 3A 3.3 η Efficiency VIN = 12V, ILOAD = 3A 86 (1) (2) % Typical values are determined with TA = TJ = 25°C and represent the most likely norm. All limits are ensured at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100% tested during production with TA = TJ = 25°C. All limits at temperature extremes are ensured via correlation using standard Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). LM2673-5.0 Symbol Parameter Conditions Typ (1) Min (2) Max (2) 4.900/4.850 5.100/5.150 VOUT Output Voltage VIN = 8V to 40V, 100mA ≤ IOUT ≤ 3A 5.0 η Efficiency VIN = 12V, ILOAD = 3A 88 (1) (2) Units V % Typical values are determined with TA = TJ = 25°C and represent the most likely norm. All limits are ensured at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100% tested during production with TA = TJ = 25°C. All limits at temperature extremes are ensured via correlation using standard Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). LM2673-12 Symbol Parameter Conditions Typ (1) Min (2) Max (2) Units 11.76/11.64 12.24/12.36 V VOUT Output Voltage VIN = 15V to 40V, 100mA ≤ IOUT ≤ 3A 12 η Efficiency VIN = 24V, ILOAD = 3A 94 (1) (2) % Typical values are determined with TA = TJ = 25°C and represent the most likely norm. All limits are ensured at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100% tested during production with TA = TJ = 25°C. All limits at temperature extremes are ensured via correlation using standard Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). LM2673-ADJ Symbol Parameter Conditions VFB Feedback Voltage VIN = 8V to 40V, 100mA ≤ IOUT ≤ 3A VOUT Programmed for 5V η Efficiency VIN = 12V, ILOAD = 3A (1) (2) Typ (1) Min (2) Max (2) Units 1.21 1.186/1.174 1.234/1.246 V 88 % Typical values are determined with TA = TJ = 25°C and represent the most likely norm. All limits are ensured at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100% tested during production with TA = TJ = 25°C. All limits at temperature extremes are ensured via correlation using standard Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 3 LM2673 SNVS030N – APRIL 2000 – REVISED APRIL 2013 www.ti.com All Output Voltage Versions Electrical Characteristics Limits appearing in bold type face apply over the entire junction temperature range of operation, −40°C to 125°C. Specifications appearing in normal type apply for TA = TJ = 25°C. Unless otherwise specified, RADJ = 8.2KΩ, VIN=12V for the 3.3V, 5V and Adjustable versions and VIN=24V for the 12V version. Symbol Parameter Conditions Typ Min Max Units 6 mA DEVICE PARAMETERS IQ Quiescent Current VFEEDBACK = 8V 4.2 For 3.3V, 5.0V, and ADJ Versions VFEEDBACK = 15V For 12V Versions VADJ Current Limit Adjust Voltage ICL Current Limit IL 1.21 1.181/1.169 1.229/1.246 V RADJ = 8.2KΩ (1) 4.5 3.8/3.6 5.25/5.4 A Output Leakage Current VIN = 40V, Softstart Pin = 0V VSWITCH = 0V VSWITCH = −1V 1.0 6 1.5 15 RDS(ON) Switch OnResistance ISWITCH = 3A 0.15 0.17/0.29 Ω fO Oscillator Frequency Measured at Switch Pin 260 280 kHz D Duty Cycle Maximum Duty Cycle 91 % Minimum Duty Cycle 0 % VFEEDBACK = 1.3V ADJ Version Only 85 nA IBIAS Feedback Bias Current VSFST Softstart Threshold Voltage ISFST Softstart Pin Current 0.63 Softstart Pin = 0V 3.7 NDZ Package, Junction to Ambient (2) 65 NDZ Package, Junction to Ambient (3) 45 θJC NDZ Package, Junction to Case 2 θJA KTW Package, Junction to Ambient (4) 56 θJA KTW Package, Junction to Ambient (5) 35 θJA KTW Package, Junction to Ambient (6) 26 θJC KTW Package, Junction to Case 2 θJA NHM Package, Junction to Ambient (7) 55 θJA NHM Package, Junction to Ambient (8) 29 θJA θJA (1) (2) (3) (4) (5) (6) (7) (8) 4 Thermal Resistance 225 0.53 mA mA 0.74 V 6.9 μA °C/W ++ °C/W The peak switch current limit is determined by the following relationship: ICL=37,125/ RADJ. Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with ½ inch leads in a socket, or on a PC board with minimum copper area. Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with ½ inch leads soldered to a PC board containing approximately 4 square inches of (1 oz.) copper area surrounding the leads. Junction to ambient thermal resistance for the 7 lead DDPAK mounted horizontally against a PC board area of 0.136 square inches (the same size as the DDPAK package) of 1 oz. (0.0014 in. thick) copper. Junction to ambient thermal resistance for the 7 lead DDPAK mounted horizontally against a PC board area of 0.4896 square inches (3.6 times the area of the DDPAK package) of 1 oz. (0.0014 in. thick) copper. Junction to ambient thermal resistance for the 7 lead DDPAK mounted horizontally against a PC board copper area of 1.0064 square inches (7.4 times the area of the DDPAK package) of 1 oz. (0.0014 in. thick) copper. Additional copper area will reduce thermal resistance further. See the thermal model in Switchers Made Simple® software. Junction to ambient thermal resistance for the 14-lead VSON mounted on a PC board copper area equal to the die attach paddle. Junction to ambient thermal resistance for the 14-lead VSON mounted on a PC board copper area using 12 vias to a second layer of copper equal to die attach paddle. Additional copper area will reduce thermal resistance further. For layout recommendations, refer to Application Note AN-1187 at www.ti.com/lsds/ti/analog/powermanagement/power_portal.page. Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 LM2673 www.ti.com SNVS030N – APRIL 2000 – REVISED APRIL 2013 Typical Performance Characteristics Normalized Output Voltage Line Regulation Figure 4. Figure 5. Efficiency vs Input Voltage Efficiency vs ILOAD Figure 6. Figure 7. Switch Current Limit Operating Quiescent Current Figure 8. Figure 9. Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 5 LM2673 SNVS030N – APRIL 2000 – REVISED APRIL 2013 www.ti.com Typical Performance Characteristics (continued) Switching Frequency Feedback Pin Bias Current Figure 10. Figure 11. Load Transient Response for Continuous Mode VIN = 20V, VOUT = 5V L = 33 μH, COUT = 200 μF, COUTESR = 26 mΩ Load Transient Response for Discontinuous Mode VIN = 20V, VOUT = 5V, L = 10 μH, COUT = 400 μF, COUTESR = 13 mΩ A: Output Voltage, 100 mV//div, AC-Coupled. B: Load Current: 500 mA to 3A Load Pulse Figure 12. Horizontal Time Base: 100 μs/div A: Output Voltage, 100 mV/div, AC-Coupled. B: Load Current: 200 mA to 3A Load Pulse Figure 13. Horizontal Time Base: 200 μs/div Continuous Mode Switching Waveforms VIN = 20V, VOUT = 5V, ILOAD = 3A L = 33 μH, COUT = 200 μF, COUTESR = 26 mΩ Discontinuous Mode Switching Waveforms VIN = 20V, VOUT = 5V, ILOAD = 500 mA L = 10 μH, COUT = 400 μF, COUTESR = 13 mΩ A: VSW Pin Voltage, 10 V/div. B: Inductor Current, 1 A/div C: Output Ripple Voltage, 20 mV/div AC-Coupled Figure 14. Horizontal Time Base: 1 μs/div 6 A: VSW Pin Voltage, 10 V/div. B: Inductor Current, 1 A/div C: Output Ripple Voltage, 20 mV/div AC-Coupled Figure 15. Horizontal Time Base: 1 μs//iv Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 LM2673 www.ti.com SNVS030N – APRIL 2000 – REVISED APRIL 2013 Block Diagram * Active Inductor Patent Number 5,514,947 † Active Capacitor Patent Number 5,382,918 Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 7 LM2673 SNVS030N – APRIL 2000 – REVISED APRIL 2013 www.ti.com APPLICATION HINTS The LM2673 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 3A, and highly efficient operation. The LM2673 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 a design software program called LM267X Made Simple (version 2.0) a complete switching power supply can be designed quickly. The software is provided free of charge and can be downloaded from Texas Instrument's Internet site located at www.ti.com. 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 260KHz oscillator. In a standard step-down application the duty cycle (Time ON/Time OFF) of the power switch is proportional to the ratio of the power supply output voltage to the input voltage. The voltage on pin 1 switches between Vin (switch ON) and below ground by the voltage drop of the external Schottky diode (switch OFF). INPUT The input voltage for the power supply is connected to pin 2. In addition to providing energy to the load the input voltage also provides bias for the internal circuitry of the LM2673. For ensured performance the input voltage must be in the range of 8V to 40V. For best performance of the power supply the input pin should always be bypassed with an input capacitor located close to pin 2. C BOOST A capacitor must be connected from pin 3 to the switch output, pin 1. 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 0.01μF. GROUND 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 LM2673, it is recommended that a broad ground plane be used to minimize signal coupling throughout the circuit CURRENT ADJUST A key feature of the LM2673 is the ability to tailor the peak switch current limit to a level required by a particular application. This alleviates the need to use external components that must be physically sized to accommodate current levels (under shorted output conditions for example) that may be much higher than the normal circuit operating current requirements. A resistor connected from pin 5 to ground establishes a current (I(pin 5) = 1.2V / RADJ) that sets the peak current through the power switch. The maximum switch current is fixed at a level of 37,125 / RADJ. FEEDBACK This is the input to a two-stage high gain amplifier, which drives the PWM controller. It is necessary to connect pin 6 to the actual output of the power supply to set the dc output voltage. For the fixed output devices (3.3V, 5V and 12V outputs), a direct wire connection to the output is all that is required as internal gain setting resistors are provided inside the LM2673. 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. 8 Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 LM2673 www.ti.com SNVS030N – APRIL 2000 – REVISED APRIL 2013 SOFTSTART A capacitor connected from pin 7 to ground allows for a slow turn-on of the switching regulator. The capacitor sets a time delay to gradually increase the duty cycle of the internal power switch. This can significantly reduce the amount of surge current required from the input supply during an abrupt application of the input voltage. If softstart is not required this pin should be left open circuited. Please see the Css SOFTSTART CAPACITOR section for further information regarding softstart capacitor values. DAP (VSON PACKAGE) The Die Attach Pad (DAP) can and should be connected to PCB Ground plane/island. For CAD and assembly guidelines refer to Application Note AN-1187 at www.ti.com/lsds/ti/analog/powermanagement/power_portal.page. DESIGN CONSIDERATIONS Figure 16. Basic Circuit for Fixed Output Voltage Applications Figure 17. Basic Circuit for Adjustable Output Voltage Applications Power supply design using the LM2673 is greatly simplified by using recommended external components. A wide range of inductors, capacitors and Schottky diodes from several manufacturers have been evaluated for use in designs that cover the full range of capabilities (input voltage, output voltage and load current) of the LM2673. A simple design procedure using nomographs and component tables provided in this data sheet leads to a working design with very little effort. Alternatively, the design software, LM267X Made Simple (version 6.0), can also be used to provide instant component selection, circuit performance calculations for evaluation, a bill of materials component list and a circuit schematic. Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 9 LM2673 SNVS030N – APRIL 2000 – REVISED APRIL 2013 www.ti.com The individual components from the various manufacturers called out for use are still just a small sample of the vast array of components available in the industry. While these components are recommended, they are not exclusively the only components for use in a design. After a close comparison of component specifications, equivalent devices from other manufacturers could be substituted for use in an application. Important considerations for each external component and an explanation of how the nomographs and selection tables were developed follows. INDUCTOR The inductor is the key component in a switching regulator. For efficiency the inductor stores energy during the switch ON time and then transfers energy to the load while the switch is OFF. Nomographs are used to select the inductance value required for a given set of operating conditions. The nomographs assume that the circuit is operating in continuous mode (the current flowing through the inductor never falls to zero). The magnitude of inductance is selected to maintain a maximum ripple current of 30% of the maximum load current. If the ripple current exceeds this 30% limit the next larger value is selected. The inductors offered have been specifically manufactured to provide proper operation under all operating conditions of input and output voltage and load current. Several part types are offered for a given amount of inductance. Both surface mount and through-hole devices are available. The inductors from each of the three manufacturers have unique characteristics. Renco: ferrite stick core inductors; benefits are typically lowest cost and can withstand ripple and transient peak currents above the rated value. These inductors have an external magnetic field, which may generate EMI. Pulse Engineering: powdered iron toroid core inductors; these also can withstand higher than rated currents and, being toroid inductors, will have low EMI. Coilcraft: ferrite drum core inductors; these are the smallest physical size inductors and are available only as surface mount components. These inductors also generate EMI but less than stick inductors. OUTPUT CAPACITOR The output capacitor acts to smooth the dc output voltage and also provides energy storage. Selection of an output capacitor, with an associated equivalent series resistance (ESR), impacts both the amount of output ripple voltage and stability of the control loop. The output ripple voltage of the power supply is the product of the capacitor ESR and the inductor ripple current. The capacitor types recommended in the tables were selected for having low ESR ratings. In addition, both surface mount tantalum capacitors and through-hole aluminum electrolytic capacitors are offered as solutions. Impacting frequency stability of the overall control loop, the output capacitance, in conjunction with the inductor, creates a double pole inside the feedback loop. In addition the capacitance and the ESR value create a zero. These frequency response effects together with the internal frequency compensation circuitry of the LM2673 modify the gain and phase shift of the closed loop system. As a general rule for stable switching regulator circuits it is desired to have the unity gain bandwidth of the circuit to be limited to no more than one-sixth of the controller switching frequency. With the fixed 260KHz switching frequency of the LM2673, the output capacitor is selected to provide a unity gain bandwidth of 40KHz maximum. Each recommended capacitor value has been chosen to achieve this result. In some cases multiple capacitors are required either to reduce the ESR of the output capacitor, to minimize output ripple (a ripple voltage of 1% of Vout or less is the assumed performance condition), or to increase the output capacitance to reduce the closed loop unity gain bandwidth (to less than 40KHz). When parallel combinations of capacitors are required it has been assumed that each capacitor is the exact same part type. 10 Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 LM2673 www.ti.com SNVS030N – APRIL 2000 – REVISED APRIL 2013 The RMS current and working voltage (WV) ratings of the output capacitor are also important considerations. In a typical step-down switching regulator, the inductor ripple current (set to be no more than 30% of the maximum load current by the inductor selection) is the current that flows through the output capacitor. The capacitor RMS current rating must be greater than this ripple current. The voltage rating of the output capacitor should be greater than 1.3 times the maximum output voltage of the power supply. If operation of the system at elevated temperatures is required, the capacitor voltage rating may be de-rated to less than the nominal room temperature rating. Careful inspection of the manufacturer's specification for de-rating of working voltage with temperature is important. INPUT CAPACITOR Fast changing currents in high current switching regulators place a significant dynamic load on the unregulated power source. An input capacitor helps to provide additional current to the power supply as well as smooth out input voltage variations. Like the output capacitor, the key specifications for the input capacitor are RMS current rating and working voltage. The RMS current flowing through the input capacitor is equal to one-half of the maximum dc load current so the capacitor should be rated to handle this. Paralleling multiple capacitors proportionally increases the current rating of the total capacitance. The voltage rating should also be selected to be 1.3 times the maximum input voltage. Depending on the unregulated input power source, under light load conditions the maximum input voltage could be significantly higher than normal operation and should be considered when selecting an input capacitor. The input capacitor should be placed very close to the input pin of the LM2673. Due to relative high current operation with fast transient changes, the series inductance of input connecting wires or PCB traces can create ringing signals at the input terminal which could possibly propagate to the output or other parts of the circuitry. It may be necessary in some designs to add a small valued (0.1μF to 0.47μF) ceramic type capacitor in parallel with the input capacitor to prevent or minimize any ringing. CATCH DIODE When the power switch in the LM2673 turns OFF, the current through the inductor continues to flow. The path for this current is through the diode connected between the switch output and ground. This forward biased diode clamps the switch output to a voltage less than ground. This negative voltage must be greater than −1V so a low voltage drop (particularly at high current levels) Schottky diode is recommended. Total efficiency of the entire power supply is significantly impacted by the power lost in the output catch diode. The average current through the catch diode is dependent on the switch duty cycle (D) and is equal to the load current times (1-D). Use of a diode rated for much higher current than is required by the actual application helps to minimize the voltage drop and power loss in the diode. During the switch ON time the diode will be reversed biased by the input voltage. The reverse voltage rating of the diode should be at least 1.3 times greater than the maximum input voltage. BOOST CAPACITOR The boost capacitor creates a voltage used to overdrive the gate of the internal power MOSFET. This improves efficiency by minimizing the on resistance of the switch and associated power loss. For all applications it is recommended to use a 0.01μF/50V ceramic capacitor. RADJ, ADJUSTABLE CURRENT LIMIT A key feature of the LM2673 is the ability to control the peak switch current. Without this feature the peak switch current would be internally set to 5A or higher to accommodate 3A load current designs. This requires that both the inductor (which could saturate with excessively high currents) and the catch diode be able to safely handle up to 5A which would be conducted under load fault conditions. If an application only requires a load current of 2A or so the peak switch current can be set to a limit just over the maximum load current with the addition of a single programming resistor. This allows the use of less powerful and more cost effective inductors and diodes. Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 11 LM2673 SNVS030N – APRIL 2000 – REVISED APRIL 2013 www.ti.com The peak switch current is equal to a factor of 37,125 divided by RADJ. A resistance of 8.2KΩ sets the current limit to typically 4.5A. For predictable control of the current limit it is recommended to keep the peak switch current greater than 1A. For lower current applications 500mA and 1A switching regulators, the LM2674 and LM2672, are available. When the power switch reaches the current limit threshold it is immediately turned OFF and the internal switching frequency is reduced. This extends the OFF time of the switch to prevent a steady state high current condition. As the switch current falls below the current limit threshold, the switch will turn back ON. If a load fault continues, the switch will again exceed the threshold and switch back OFF. This will result in a low duty cycle pulsing of the power switch to minimize the overall fault condition power dissipation. Css SOFTSTART CAPACITOR This optional capacitor controls the rate at which the LM2673 starts up at power on. The capacitor is charged linearly by an internal current source. This voltage ramp gradually increases the duty cycle of the power switch until it reaches the normal operating duty cycle defined primarily by the ratio of the output voltage to the input voltage. The softstart turn-on time is programmable by the selection of Css. The formula for selecting a softstart capacitor is: where • • • • • • ISST = Softstart Current, 3.7μA typical tSS = Softstart time, from design requirements VSST = Softstart Threshold Voltage, 0.63V typical VOUT = Output Voltage, from design requirements VSCHOTTKY = Schottky Diode Voltage Drop, typically 0.5V VIN = Maximum Input Voltage, from design requirements (1) If this feature is not desired, leave the Softstart pin (pin 7) open circuited With certain softstart capacitor values and operating conditions, the LM2673 can exhibit an overshoot on the output voltage during turn on. Especially when starting up into no load or low load, the softstart 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 softstart capacitors between 0.033µF and 1µF. ADDITIONAL APPLICATION INFORMATION When the output voltage is greater than approximately 6V, and the duty cycle at minimum input voltage is greater than approximately 50%, the designer should 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 (½CV2), thus requiring an increased charging current. 12 Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 LM2673 www.ti.com SNVS030N – APRIL 2000 – REVISED APRIL 2013 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 will recover smoothly. Practical values of external components that have been experimentally found to work well under these specific operating conditions are COUT = 47µF, L = 22µH. It should be noted 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 24V and the set output voltage is 18V, then for a desired maximum current of 1.5A, the current limit of the chosen switcher must be confirmed to be at least 3A. Under extreme over-current 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 will be automatically reduced to protect the IC. Frequency below 100 KHz is typical for an extreme short circuit condition. SIMPLE DESIGN PROCEDURE Using the nomographs and tables in this data sheet (or use the available design software at www.ti.com) a complete step-down regulator can be designed in a few simple steps. Step 1: Define the power supply operating conditions: Required output voltage Maximum DC input voltage Maximum output load current Step 2: Set the output voltage by selecting a fixed output LM2673 (3.3V, 5V or 12V applications) or determine the required feedback resistors for use with the adjustable LM2673−ADJ Step 3: Determine the inductor required by using one of the four nomographs, Figure 18 through Figure 21. Table 1 provides a specific manufacturer and part number for the inductor. Step 4: Using Table 6 and Table 7 (fixed output voltage) or Table 12 and Table 13 (adjustable output voltage), determine the output capacitance required for stable operation. Table 3 and Table 13 provide the specific capacitor type from the manufacturer of choice. Step 5: Determine an input capacitor from Table 6 and Table 9 for fixed output voltage applications. Use Table 3 or Table 4 to find the specific capacitor type. For adjustable output circuits select a capacitor from Table 3 or Table 4 with a sufficient working voltage (WV) rating greater than Vin max, and an rms current rating greater than one-half the maximum load current (2 or more capacitors in parallel may be required). Step 6: Select a diode from Table 10. The current rating of the diode must be greater than I load max and the Reverse Voltage rating must be greater than Vin max. Step 7: Include a 0.01μF/50V capacitor for Cboost in the design and then determine the value of a softstart capacitor if desired. Step 8: Define a value for RADJ to set the peak switch current limit to be at least 20% greater than Iout max to allow for at least 30% inductor ripple current (±15% of Iout). For designs that must operate over the full temperature range the switch current limit should be set to at least 50% greater than Iout max (1.5 x Iout max). FIXED OUTPUT VOLTAGE DESIGN EXAMPLE A system logic power supply bus of 3.3V is to be generated from a wall adapter which provides an unregulated DC voltage of 13V to 16V. The maximum load current is 2.5A. A softstart delay time of 50mS is desired. Through-hole components are preferred. Step 1: Operating conditions are: Vout = 3.3V Vin max = 16V Iload max = 2.5A Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 13 LM2673 SNVS030N – APRIL 2000 – REVISED APRIL 2013 www.ti.com Step 2: Select an LM2673T-3.3. The output voltage will have a tolerance of ±2% at room temperature and ±3% over the full operating temperature range. Step 3: Use the nomograph for the 3.3V device, Figure 18. The intersection of the 16V horizontal line (Vin max) and the 2.5A vertical line (Iload max) indicates that L33, a 22μH inductor, is required. From Table 1, L33 in a through-hole component is available from Renco with part number RL-1283-22-43 or part number PE-53933 from Pulse Engineering. Step 4: Use Table 6 or Table 7 to determine an output capacitor. With a 3.3V output and a 33μH inductor there are four through-hole output capacitor solutions with the number of same type capacitors to be paralleled and an identifying capacitor code given. Table 3 or Table 4 provide the actual capacitor characteristics. Any of the following choices will work in the circuit: 1 x 220μF/10V Sanyo OS-CON (code C5) 1 x 1000μF/35V Sanyo MV-GX (code C10) 1 x 2200μF/10V Nichicon PL (code C5) 1 x 1000μF/35V Panasonic HFQ (code C7) Step 5: Use Table 6 or Table 9 to select an input capacitor. With 3.3V output and 22μH there are three throughhole solutions. These capacitors provide a sufficient voltage rating and an rms current rating greater than 1.25A (1/2 Iload max). Again using Table 3 or Table 4 for specific component characteristics the following choices are suitable: 1 x 1000μF/63V Sanyo MV-GX (code C14) 1 x 820μF/63V Nichicon PL (code C24) 1 x 560μF/50V Panasonic HFQ (code C13) Step 6: From Table 10 a 3A or more Schottky diode must be selected. The 20V rated diodes are sufficient for the application and for through-hole components two part types are suitable: 1N5820 SR302 Step 7: A 0.01μF capacitor will be used for Cboost. For the 50mS softstart delay the following parameters are to be used: ISST: 3.7μA tSS: 50mS VSST: 0.63V VOUT: 3.3V VSCHOTTKY: 0.5V VIN: 16V Using Vin max ensures that the softstart delay time will be at least the desired 50mS. Using the formula for Css a value of 0.148μF is determined to be required. Use of a standard value 0.22μF capacitor will produce more than sufficient softstart delay. Step 8: Determine a value for RADJ to provide a peak switch current limit of at least 2.5A plus 50% or 3.75A. (2) Use a value of 10KΩ. 14 Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 LM2673 www.ti.com SNVS030N – APRIL 2000 – REVISED APRIL 2013 ADJUSTABLE OUTPUT DESIGN EXAMPLE In this example it is desired to convert the voltage from a two battery automotive power supply (voltage range of 20V to 28V, typical in large truck applications) to the 14.8VDC alternator supply typically used to power electronic equipment from single battery 12V vehicle systems. The load current required is 2A maximum. It is also desired to implement the power supply with all surface mount components. Softstart is not required. Step 1: Operating conditions are: Vout = 14.8V Vin max = 28V Iload max = 2A Step 2: Select an LM2673S-ADJ. To set the output voltage to 14.9V two resistors need to be chosen (R1 and R2 in Figure 17). For the adjustable device the output voltage is set by the following relationship: where • VFB is the feedback voltage of typically 1.21V (3) A recommended value to use for R1 is 1K. In this example then R2 is determined to be: (4) R2 = 11.23KΩ The closest standard 1% tolerance value to use is 11.3KΩ This will set the nominal output voltage to 14.88V which is within 0.5% of the target value. Step 3: To use the nomograph for the adjustable device, Figure 21, requires a calculation of the inductor Volt•microsecond constant (E•T expressed in V•μS) from the following formula: where • VSAT is the voltage drop across the internal power switch which is Rds(ON) times Iload (5) In this example this would be typically 0.15Ω x 2A or 0.3V and VD is the voltage drop across the forward bisased Schottky diode, typically 0.5V. The switching frequency of 260KHz is the nominal value to use to estimate the ON time of the switch during which energy is stored in the inductor. For this example E•T is found to be: (6) (7) Using Figure 21, the intersection of 27V•μS horizontally and the 2A vertical line (Iload max) indicates that L38 , a 68μH inductor, should be used. From Table 1, L38 in a surface mount component is available from Pulse Engineering with part number PE54038S. Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 15 LM2673 SNVS030N – APRIL 2000 – REVISED APRIL 2013 www.ti.com Step 4: Use Table 12 or Table 13 to determine an output capacitor. With a 14.8V output the 12.5 to 15V row is used and with a 68μH inductor there are three surface mount output capacitor solutions. Table 3 or Table 4 provide the actual capacitor characteristics based on the C Code number. Any of the following choices can be used: 1 x 33μF/20V AVX TPS (code C6) 1 x 47μF/20V Sprague 594 (code C8) 1 x 47μF/20V Kemet T495 (code C8) NOTE When using the adjustable device in low voltage applications (less than 3V output), if the nomograph, Figure 21, selects an inductance of 22μH or less, Table 12 and Table 13 do not provide an output capacitor solution. With these conditions the number of output capacitors required for stable operation becomes impractical. It is recommended to use either a 33μH or 47μH inductor and the output capacitors from Table 12 or Table 13. Step 5: An input capacitor for this example will require at least a 35V WV rating with an rms current rating of 1A (1/2 Iout max). From Table 3 or Table 4 it can be seen that C12, a 33μF/35V capacitor from Sprague, has the required voltage/current rating of the surface mount components. Step 6: From Table 10 a 3A Schottky diode must be selected. For surface mount diodes with a margin of safety on the voltage rating one of five diodes can be used: SK34 30BQ040 30WQ04F MBRS340 MBRD340 Step 7: A 0.01μF capacitor will be used for Cboost. The softstart pin will be left open circuited. Step 8: Determine a value for RADJ to provide a peak switch current limit of at least 2A plus 50% or 3A. (8) Use a value of 12.4KΩ. VSON PACKAGE DEVICES The LM2673 is offered in the 14 lead VSON surface mount package to allow for a significantly decreased footprint with equivalent power dissipation compared to the DDPAK. For details on mounting and soldering specifications, refer to Application Note AN-1187 at www.ti.com/lsds/ti/analog/powermanagement/power_portal.page. 16 Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 LM2673 www.ti.com SNVS030N – APRIL 2000 – REVISED APRIL 2013 Inductor Selection Guides For Continuous Mode Operation Figure 18. LM2673-3.3 Figure 19. LM2673-5.0 Figure 20. LM2673-12 Figure 21. LM2673-ADJ Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 17 LM2673 SNVS030N – APRIL 2000 – REVISED APRIL 2013 www.ti.com Table 1. Inductor Manufacturer Part Numbers Inductor Reference Number Inductance (µH) Current (A) L23 33 L24 22 L25 Renco Pulse Engineering Through Hole Surface Mount 1.35 RL-5471-7 RL1500-33 PE-53823 PE-53823S DO3316-333 1.65 RL-1283-22-43 RL1500-22 PE-53824 PE-53824S DO3316-223 15 2.00 RL-1283-15-43 RL1500-15 PE-53825 PE-53825S DO3316-153 L29 100 1.41 RL-5471-4 RL-6050-100 PE-53829 PE-53829S DO5022P-104 L30 68 1.71 RL-5471-5 RL6050-68 PE-53830 PE-53830S DO5022P-683 L31 47 2.06 RL-5471-6 RL6050-47 PE-53831 PE-53831S DO5022P-473 L32 33 2.46 RL-5471-7 RL6050-33 PE-53932 PE-53932S DO5022P-333 L33 22 3.02 RL-1283-22-43 RL6050-22 PE-53933 PE-53933S DO5022P-223 L34 15 3.65 RL-1283-15-43 — PE-53934 PE-53934S DO5022P-153 L38 68 2.97 RL-5472-2 — PE-54038 PE-54038S — L39 47 3.57 RL-5472-3 — PE-54039 PE-54039S — L40 33 4.26 RL-1283-33-43 — PE-54040 PE-54040S — L41 22 5.22 RL-1283-22-43 — PE-54041 P0841 — L44 68 3.45 RL-5473-3 — PE-54044 L45 10 4.47 RL-1283-10-43 — — Surface Mount Coilcraft Through Hole — P0845 Surface Mount — DO5022P-103HC Table 2. Inductor Manufacturer Contact Numbers Coilcraft Coilcraft, Europe Pulse Engineering Pulse Engineering, Europe Renco Electronics 18 Phone (800) 322-2645 FAX (708) 639-1469 Phone +44 1236 730 595 FAX +44 1236 730 627 Phone (619) 674-8100 FAX (619) 674-8262 Phone +353 93 24 107 FAX +353 93 24 459 Phone (800) 645-5828 FAX (516) 586-5562 Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 LM2673 www.ti.com SNVS030N – APRIL 2000 – REVISED APRIL 2013 Capacitor Selection Guides Table 3. Input and Output Capacitor Codes—Surface Mount Surface Mount Capacitor Reference Code AVX TPS Series Sprague 594D Series Kemet T495 Series C (µF) WV (V) Irms (A) C (µF) WV (V) Irms (A) C (µF) WV (V) Irms (A) C1 330 6.3 1.15 120 6.3 1.1 100 6.3 0.82 C2 100 10 1.1 220 6.3 1.4 220 6.3 1.1 C3 220 10 1.15 68 10 1.05 330 6.3 1.1 C4 47 16 0.89 150 10 1.35 100 10 1.1 C5 100 16 1.15 47 16 1 150 10 1.1 C6 33 20 0.77 100 16 1.3 220 10 1.1 C7 68 20 0.94 180 16 1.95 33 20 0.78 C8 22 25 0.77 47 20 1.15 47 20 0.94 C9 10 35 0.63 33 25 1.05 68 20 0.94 C10 22 35 0.66 68 25 1.6 10 35 0.63 C11 15 35 0.75 22 35 0.63 C12 33 35 1 4.7 50 0.66 C13 15 50 0.9 Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 19 LM2673 SNVS030N – APRIL 2000 – REVISED APRIL 2013 www.ti.com Table 4. Input and Output Capacitor Codes—Through Hole Through Hole Capacitor Reference Code Sanyo OS-CON SA Series C (µF) WV (V) C1 47 C2 150 C3 C4 C5 Sanyo MV-GX Series Nichicon PL Series Irms (A) C (µF) WV (V) Irms (A) C (µF) WV (V) 6.3 1 1000 6.3 0.8 680 10 6.3 1.95 270 16 0.6 820 10 330 6.3 2.45 470 16 0.75 1000 10 100 10 1.87 560 16 0.95 1200 10 220 10 2.36 820 16 1.25 2200 C6 33 16 0.96 1000 16 1.3 C7 100 16 1.92 150 35 0.65 C8 150 16 2.28 470 35 C9 100 20 2.25 680 35 C10 47 25 2.09 Irms (A) Panasonic HFQ Series C (µF) WV (V) Irms (A) 0.8 82 35 0.4 0.98 120 35 0.44 1.06 220 35 0.76 1.28 330 35 1.01 10 1.71 560 35 1.4 3300 10 2.18 820 35 1.62 3900 10 2.36 1000 35 1.73 1.3 6800 10 2.68 2200 35 2.8 1.4 180 16 0.41 56 50 0.36 1000 35 1.7 270 16 0.55 100 50 0.5 C11 220 63 0.76 470 16 0.77 220 50 0.92 C12 470 63 1.2 680 16 1.02 470 50 1.44 C13 680 63 1.5 820 16 1.22 560 50 1.68 C14 1000 63 1.75 1800 16 1.88 1200 50 2.22 C15 220 25 0.63 330 63 1.42 C16 220 35 0.79 1500 63 2.51 C17 560 35 1.43 C18 2200 35 2.68 C19 150 50 0.82 C20 220 50 1.04 C21 330 50 1.3 C22 100 63 0.75 C23 390 63 1.62 C24 820 63 2.22 C25 1200 63 2.51 Table 5. Capacitor Manufacturer Contact Numbers Nichicon Panasonic AVX Sprague/Vishay Sanyo Kemet 20 Phone (847) 843-7500 FAX (847) 843-2798 Phone (714) 373-7857 FAX (714) 373-7102 Phone (845) 448-9411 FAX (845) 448-1943 Phone (207) 324-4140 FAX (207) 324-7223 Phone (619) 661-6322 FAX (619) 661-1055 Phone (864) 963-6300 FAX (864) 963-6521 Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 LM2673 www.ti.com SNVS030N – APRIL 2000 – REVISED APRIL 2013 Table 6. Output Capacitors for Fixed Output Voltage Application—Surface Mount (1) (2) Surface Mount Output Voltage (V) Inductance (µH) 3.3 5 12 (1) (2) AVX TPS Series Sprague 594D Series Kemet T495 Series No. C Code No. C Code No. C Code 10 4 C2 3 C1 4 C4 15 4 C2 3 C1 4 C4 22 3 C2 2 C7 3 C4 33 2 C2 2 C6 2 C4 10 4 C2 4 C6 4 C4 15 3 C2 2 C7 3 C4 22 3 C2 2 C7 3 C4 33 2 C2 2 C3 2 C4 47 2 C2 1 C7 2 C4 10 4 C5 3 C6 5 C9 15 3 C5 2 C7 4 C8 22 2 C5 2 C6 3 C8 33 2 C5 1 C7 2 C8 47 2 C4 1 C6 2 C8 68 1 C5 1 C5 2 C7 100 1 C4 1 C5 1 C8 No. represents the number of identical capacitor types to be connected in parallel C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer. Table 7. Output Capacitors for Fixed Output Voltage Application—Through Hole (1) (2) Through Hole Output Voltage (V) 3.3 5 12 (1) (2) Inductance (µH) Sanyo OS-CON SA Series Sanyo MV-GX Series Nichicon PL Series Panasonic HFQ Series No. C Code No. C Code No. C Code No. C Code 10 1 C3 1 C10 1 C6 2 C6 15 1 C3 1 C10 1 C6 2 C5 22 1 C5 1 C10 1 C5 1 C7 33 1 C2 1 C10 1 C13 1 C5 10 2 C4 1 C10 1 C6 2 C5 15 1 C5 1 C10 1 C5 1 C6 22 1 C5 1 C5 1 C5 1 C5 33 1 C4 1 C5 1 C13 1 C5 47 1 C4 1 C4 1 C13 2 C3 10 2 C7 2 C5 1 C18 2 C5 15 1 C8 1 C5 1 C17 1 C5 22 1 C7 1 C5 1 C13 1 C5 33 1 C7 1 C3 1 C11 1 C4 47 1 C7 1 C3 1 C10 1 C3 68 1 C7 1 C2 1 C10 1 C3 100 1 C7 1 C2 1 C9 1 C1 No. represents the number of identical capacitor types to be connected in parallel C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer. Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 21 LM2673 SNVS030N – APRIL 2000 – REVISED APRIL 2013 www.ti.com Table 8. Input Capacitors for Fixed Output Voltage Application—Surface Mount (1) (2) (3) Surface Mount Output Voltage (V) Inductance (µH) 3.3 5 12 (1) (2) (3) (4) AVX TPS Series Sprague 594D Series Kemet T495 Series No. C Code No. C Code No. 10 2 C5 1 C7 2 C8 15 3 C9 1 C10 3 C10 22 See (4) See (4) 2 C13 3 C12 33 See (4) (4) 2 C13 2 C12 10 2 C5 1 C7 2 C8 15 2 C5 1 C7 2 C8 See C Code 22 3 C10 2 C12 3 C11 33 See (4) See (4) 2 C13 3 C12 47 See (4) See (4) 1 C13 2 C12 10 2 C7 2 C10 2 C7 15 2 C7 2 C10 2 C7 22 3 C10 2 C12 3 C10 33 3 C10 (4) See 2 C12 3 C10 (4) 47 See 2 C13 3 C12 68 See (4) See (4) 2 C13 2 C12 100 See (4) See (4) 1 C13 2 C12 Assumes worst case maximum input voltage and load current for a given inductance value No. represents the number of identical capacitor types to be connected in parallel C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer. Check voltage rating of capacitors to be greater than application input voltage. Table 9. Input Capacitors for Fixed Output Voltage Application—Through Hole (1) (2) (3) Through Hole Output Voltage (V) Inductance (µH) Sanyo OS-CON SA Series No. 3.3 5 12 (1) (2) (3) (4) 22 Sanyo MV-GX Series C Code No. Nichicon PL Series C Code No. Panasonic HFQ Series C Code No. C Code C6 10 1 C7 2 C4 1 C5 1 15 1 C10 1 C10 1 C18 1 C6 22 See (4) See (4) 1 C14 1 C24 1 C13 33 See (4) See (4) 1 C12 1 C20 1 C12 10 1 C7 2 C4 1 C14 1 C6 15 1 C7 2 C4 1 C14 1 C6 (4) (4) 22 See 1 C10 1 C18 1 C13 33 See (4) See See (4) 1 C14 1 C23 1 C13 47 See (4) See (4) 1 C12 1 C20 1 C12 10 1 C9 1 C10 1 C18 1 C6 15 1 C10 1 C10 1 C18 1 C6 22 1 C10 1 C10 1 C18 1 C6 33 See (4) See (4) 1 C10 1 C18 1 C6 47 See (4) (4) 1 C13 1 C23 1 C13 68 See (4) See (4) 1 C12 1 C21 1 C12 100 See (4) See (4) 1 C11 1 C22 1 C11 See Assumes worst case maximum input voltage and load current for a given inductance value No. represents the number of identical capacitor types to be connected in parallel C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer. Check voltage rating of capacitors to be greater than application input voltage. Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 LM2673 www.ti.com SNVS030N – APRIL 2000 – REVISED APRIL 2013 Table 10. Schottky Diode Selection Table Reverse Voltage (V) Surface Mount 3A 20V SK32 30V SK33 Through Hole 5A or More 3A 5A or More 1N5820 SR302 MBRD835L 30WQ03F 40V 1N5821 31DQ03 SK34 MBRB1545CT 1N5822 30BQ040 6TQ045S MBR340 MBR745 30WQ04F 31DQ04 80SQ045 MBRS340 SR403 6TQ045 MBRD340 50V or More SK35 MBR350 30WQ05F 31DQ05 SR305 Table 11. Diode Manufacturer Contact Numbers International Rectifier Motorola General Semiconductor Diodes, Inc. Phone (310) 322-3331 FAX (310) 322-3332 Phone (800) 521-6274 FAX (602) 244-6609 Phone (516) 847-3000 FAX (516) 847-3236 Phone (805) 446-4800 FAX (805) 446-4850 Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 23 LM2673 SNVS030N – APRIL 2000 – REVISED APRIL 2013 www.ti.com Table 12. Output Capacitors for Adjustable Output Voltage Applications—Surface Mount (1) (2) Surface Mount Output Voltage (V) 1.21 to 2.50 2.5 to 3.75 3.75 to 5 5 to 6.25 6.25 to 7.5 7.5 to 10 10 to 12.5 12.5 to 15 15 to 20 20 to 30 30 to 37 (1) (2) (3) 24 Inductance (µH) AVX TPS Series Sprague 594D Series Kemet T495 Series No. C Code No. C Code No. C Code 33 (3) 7 C1 6 C2 7 C3 47 (3) 5 C1 4 C2 5 C3 33 (3) 4 C1 3 C2 4 C3 (3) 47 3 C1 2 C2 3 C3 22 4 C1 3 C2 4 C3 33 3 C1 2 C2 3 C3 47 2 C1 2 C2 2 C3 22 3 C2 3 C3 3 C4 33 2 C2 2 C3 2 C4 47 2 C2 2 C3 2 C4 68 1 C2 1 C3 1 C4 22 3 C2 1 C4 3 C4 33 2 C2 1 C3 2 C4 47 1 C3 1 C4 1 C6 68 1 C2 1 C3 1 C4 33 2 C5 1 C6 2 C8 47 1 C5 1 C6 2 C8 68 1 C5 1 C6 1 C8 100 1 C4 1 C5 1 C8 33 1 C5 1 C6 2 C8 47 1 C5 1 C6 2 C8 68 1 C5 1 C6 1 C8 100 1 C5 1 C6 1 C8 33 1 C6 1 C8 1 C8 47 1 C6 1 C8 1 C8 68 1 C6 1 C8 1 C8 100 1 C6 1 C8 1 C8 33 1 C8 1 C10 2 C10 47 1 C8 1 C9 2 C10 68 1 C8 1 C9 2 C10 100 1 C8 1 C9 1 C10 33 2 C9 2 C11 2 C11 47 1 C10 1 C12 1 C11 68 1 C9 1 C12 1 C11 100 1 C9 1 C12 1 C11 10 4 C13 8 C12 15 3 C13 5 C12 22 2 C13 4 C12 1 C13 3 C12 47 1 C13 2 C12 68 1 C13 2 C12 33 No Values Available No. represents the number of identical capacitor types to be connected in parallel C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer. Set to a higher value for a practical design solution. See Application Hints section Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 LM2673 www.ti.com SNVS030N – APRIL 2000 – REVISED APRIL 2013 Table 13. Output Capacitors for Adjustable Output Voltage Applications—Through Hole (1) (2) Through Hole Output Voltage (V) 1.21 to 2.50 2.5 to 3.75 3.75 to 5 5 to 6.25 6.25 to 7.5 7.5 to 10 10 to 12.5 12.5 to 15 15 to 20 Inductance (µH) Sanyo OS-CON SA Series 30 to 37 (1) (2) (3) Nichicon PL Series Panasonic HFQ Series No. C Code No. C Code No. C Code No. 33 (3) 2 C3 5 C1 5 C3 3 C 47 (3) 2 C2 4 C1 3 C3 2 C5 33 (3) 1 C3 3 C1 3 C1 2 C5 47 (3) 1 C2 2 C1 2 C3 1 C5 22 1 C3 3 C1 3 C1 2 C5 33 1 C2 2 C1 2 C1 1 C5 47 1 C2 2 C1 1 C3 1 C5 22 1 C5 2 C6 2 C3 2 C5 33 1 C4 1 C6 2 C1 1 C5 47 1 C4 1 C6 1 C3 1 C5 68 1 C4 1 C6 1 C1 1 C5 22 1 C5 1 C6 2 C1 1 C5 33 1 C4 1 C6 1 C3 1 C5 47 1 C4 1 C6 1 C1 1 C5 68 1 C4 1 C2 1 C1 1 C5 33 1 C7 1 C6 1 C14 1 C5 47 1 C7 1 C6 1 C14 1 C5 68 1 C7 1 C2 1 C14 1 C2 100 1 C7 1 C2 1 C14 1 C2 33 1 C7 1 C6 1 C14 1 C5 47 1 C7 1 C2 1 C14 1 C5 68 1 C7 1 C2 1 C9 1 C2 100 1 C7 1 C2 1 C9 1 C2 33 1 C9 1 C10 1 C15 1 C2 47 1 C9 1 C10 1 C15 1 C2 C Code 68 1 C9 1 C10 1 C15 1 C2 100 1 C9 1 C10 1 C15 1 C2 33 1 C10 1 C7 1 C15 1 C2 47 1 C10 1 C7 1 C15 1 C2 68 1 C10 1 C7 1 C15 1 C2 100 1 C10 1 C7 1 C15 1 C2 1 C7 1 C16 1 C2 1 C7 1 C16 1 C2 1 C7 1 C16 1 C2 100 1 C7 1 C16 1 C2 10 1 C12 1 C20 1 C10 15 1 C11 1 C20 1 C11 22 1 C11 1 C20 1 C10 1 C11 1 C20 1 C10 47 1 C11 1 C20 1 C10 68 1 C11 1 C20 1 C10 33 20 to 30 Sanyo MV-GX Series 47 68 33 No Values Available No Values Available No. represents the number of identical capacitor types to be connected in parallel C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer. Set to a higher value for a practical design solution. See Application Hints section Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 25 LM2673 SNVS030N – APRIL 2000 – REVISED APRIL 2013 www.ti.com REVISION HISTORY Changes from Revision M (April 2013) to Revision N • 26 Page Changed layout of National Data Sheet to TI format .......................................................................................................... 25 Submit Documentation Feedback Copyright © 2000–2013, Texas Instruments Incorporated Product Folder Links: LM2673 PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 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) LM2673S-12 NRND DDPAK/ TO-263 KTW 7 45 TBD Call TI Call TI -40 to 125 LM2673 S-12 LM2673S-12/NOPB ACTIVE DDPAK/ TO-263 KTW 7 45 Pb-Free (RoHS Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2673 S-12 LM2673S-3.3 NRND DDPAK/ TO-263 KTW 7 45 TBD Call TI Call TI -40 to 125 LM2673 S-3.3 LM2673S-3.3/NOPB ACTIVE DDPAK/ TO-263 KTW 7 45 Pb-Free (RoHS Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2673 S-3.3 LM2673S-5.0 NRND DDPAK/ TO-263 KTW 7 45 TBD Call TI Call TI -40 to 125 LM2673 S-5.0 LM2673S-5.0/NOPB ACTIVE DDPAK/ TO-263 KTW 7 45 Pb-Free (RoHS Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2673 S-5.0 LM2673S-ADJ NRND DDPAK/ TO-263 KTW 7 45 TBD Call TI Call TI -40 to 125 LM2673 S-ADJ LM2673S-ADJ/NOPB ACTIVE DDPAK/ TO-263 KTW 7 45 Pb-Free (RoHS Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2673 S-ADJ LM2673SD-12/NOPB ACTIVE VSON NHM 14 250 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 S0002SB LM2673SD-3.3/NOPB ACTIVE VSON NHM 14 250 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 S0002TB LM2673SD-5.0/NOPB ACTIVE VSON NHM 14 250 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 S0002UB LM2673SD-ADJ/NOPB ACTIVE VSON NHM 14 250 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 S0002VB LM2673SDX-3.3/NOPB ACTIVE VSON NHM 14 2500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 S0002TB LM2673SDX-5.0/NOPB ACTIVE VSON NHM 14 2500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 S0002UB LM2673SDX-ADJ/NOPB ACTIVE VSON NHM 14 2500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 S0002VB LM2673SX-12/NOPB ACTIVE DDPAK/ TO-263 KTW 7 500 Pb-Free (RoHS Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2673 S-12 LM2673SX-3.3/NOPB ACTIVE DDPAK/ TO-263 KTW 7 500 Pb-Free (RoHS Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2673 S-3.3 Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 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) LM2673SX-5.0 NRND DDPAK/ TO-263 KTW 7 500 TBD Call TI Call TI -40 to 125 LM2673 S-5.0 LM2673SX-5.0/NOPB ACTIVE DDPAK/ TO-263 KTW 7 500 Pb-Free (RoHS Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2673 S-5.0 LM2673SX-ADJ NRND DDPAK/ TO-263 KTW 7 500 TBD Call TI Call TI -40 to 125 LM2673 S-ADJ LM2673SX-ADJ/NOPB ACTIVE DDPAK/ TO-263 KTW 7 500 Pb-Free (RoHS Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2673 S-ADJ LM2673T-12/NOPB ACTIVE TO-220 NDZ 7 45 Green (RoHS & no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2673 T-12 LM2673T-3.3/NOPB ACTIVE TO-220 NDZ 7 45 Green (RoHS & no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2673 T-3.3 LM2673T-5.0 NRND TO-220 NDZ 7 45 TBD Call TI Call TI -40 to 125 LM2673 T-5.0 LM2673T-5.0/NOPB ACTIVE TO-220 NDZ 7 45 Green (RoHS & no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2673 T-5.0 LM2673T-ADJ NRND TO-220 NDZ 7 45 TBD Call TI Call TI -40 to 125 LM2673 T-ADJ LM2673T-ADJ/NOPB ACTIVE TO-220 NDZ 7 45 Green (RoHS & no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2673 T-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) Addendum-Page 2 Samples PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 (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. 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Addendum-Page 3 PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LM2673SD-12/NOPB VSON NHM 14 250 178.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1 LM2673SD-3.3/NOPB VSON NHM 14 250 178.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1 LM2673SD-5.0/NOPB VSON NHM 14 250 178.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1 LM2673SD-ADJ/NOPB VSON NHM 14 250 178.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1 LM2673SDX-3.3/NOPB VSON NHM 14 2500 330.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1 LM2673SDX-5.0/NOPB VSON NHM 14 2500 330.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1 LM2673SDX-ADJ/NOPB VSON NHM 14 2500 330.0 16.4 5.3 6.3 1.5 12.0 16.0 Q1 LM2673SX-12/NOPB DDPAK/ TO-263 KTW 7 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2 LM2673SX-3.3/NOPB DDPAK/ TO-263 KTW 7 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2 LM2673SX-5.0 DDPAK/ TO-263 KTW 7 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2 LM2673SX-5.0/NOPB DDPAK/ TO-263 KTW 7 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2 LM2673SX-ADJ DDPAK/ TO-263 KTW 7 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2 LM2673SX-ADJ/NOPB DDPAK/ TO-263 KTW 7 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM2673SD-12/NOPB VSON NHM 14 250 210.0 185.0 35.0 LM2673SD-3.3/NOPB VSON NHM 14 250 210.0 185.0 35.0 LM2673SD-5.0/NOPB VSON NHM 14 250 210.0 185.0 35.0 LM2673SD-ADJ/NOPB VSON NHM 14 250 210.0 185.0 35.0 LM2673SDX-3.3/NOPB VSON NHM 14 2500 367.0 367.0 35.0 LM2673SDX-5.0/NOPB VSON NHM 14 2500 367.0 367.0 35.0 LM2673SDX-ADJ/NOPB VSON NHM 14 2500 367.0 367.0 35.0 LM2673SX-12/NOPB DDPAK/TO-263 KTW 7 500 367.0 367.0 45.0 LM2673SX-3.3/NOPB DDPAK/TO-263 KTW 7 500 367.0 367.0 45.0 LM2673SX-5.0 DDPAK/TO-263 KTW 7 500 367.0 367.0 45.0 LM2673SX-5.0/NOPB DDPAK/TO-263 KTW 7 500 367.0 367.0 45.0 LM2673SX-ADJ DDPAK/TO-263 KTW 7 500 367.0 367.0 45.0 LM2673SX-ADJ/NOPB DDPAK/TO-263 KTW 7 500 367.0 367.0 45.0 Pack Materials-Page 2 MECHANICAL DATA NDZ0007B TA07B (Rev E) www.ti.com MECHANICAL DATA NHM0014A SRC14A (Rev A) www.ti.com MECHANICAL DATA KTW0007B TS7B (Rev E) BOTTOM SIDE OF PACKAGE 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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