LM2672-开关电源稳压芯片-德州仪器

LM2672 SIMPLE SWITCHER Power Converter High Efficiency 1A Step-Down Voltage Regulator with Features General Description The LM2672 series of regulators are monolithic integrated circuits built with a LMDMOS process. These regulators pro- vide all the active functions for a step-down (buck) switching regulator, capable of driving a 1A load current with excellent line and load regulation. These devices are available in fixed output voltages of 3.3V, 5.0V, 12V, and an adjustable output version. Requiring a minimum number of external components, these regulators are simple to use and include patented internal fre- quency compensation (Patent Nos. 5,382,918 and 5,514,947), fixed frequency oscillator, external shutdown, soft-start, and frequency synchronization. The LM2672 series operates at a switching frequency of 260 kHz, thus allowing smaller sized filter components than what would be needed with lower frequency switching regu- lators. Because of its very high efficiency (>90%), the copper traces on the printed circuit board are the only heat sinking needed. A family of standard inductors for use with the 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 a guaranteed ±1.5% tolerance on out- put voltage within specified input voltages and output load conditions, and ±10% on the oscillator frequency. External shutdown is included, featuring typically 50 μA stand-by cur- rent. The output switch includes current limiting, as well as thermal shutdown for full protection under fault conditions. To simplify the LM2672 buck regulator design procedure, there exists computer design software, LM267X Made Sim- ple version 6.0. Features ● Efficiency up to 96% ● Available in SO-8 and 8-pin DIP packages ● Computer Design Software LM267X Made Simple version 6.0 ● Simple and easy to design with ● Requires only 5 external components ● Uses readily available standard inductors ● 3.3V, 5.0V, 12V, and adjustable output versions ● Adjustable version output voltage range: 1.21V to 37V ● ±1.5% max output voltage tolerance over line and load conditions ● Guaranteed 1A output load current ● 0.25Ω DMOS Output Switch ● Wide input voltage range: 8V to 40V ● 260 kHz fixed frequency internal oscillator ● TTL shutdown capability, low power standby mode ● Soft-start and frequency synchronization ● Thermal shutdown and current limit protection Typical Applications ● Simple High Efficiency (>90%) Step-Down (Buck) Regulator ● Efficient Pre-Regulator for Linear Regulators Typical Application (Fixed Output Voltage Versions) 1293401 SIMPLE SWITCHER® is a registered trademark of National Semiconductor Corporation WEBENCH® is a registered trademark of National Semiconductor Corporation. Windows® is a registered trademark of Microsoft Corporation. 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. 12934 SNVS136I Copyright © 1999-2012, Texas Instruments Incorporated Connection Diagrams 8-Lead Package Top View 1293402 SO-8/DIP Package See NSC Package Drawing Number MO8A/N08E 16-Lead LLP Surface Mount Package Top View 1293441 LLP Package See NSC Package Drawing Number LDA16A TABLE 1. Package Marking and Ordering Information Output Voltage Order Information Package Marking Supplied as: 16 Lead LLP 12 LM2672LD-12 S0001B 1000 Units on Tape and Reel 12 LM2672LDX-12 S0001B 4500 Units on Tape and Reel 3.3 LM2672LD-3.3 S0002B 1000 Units on Tape and Reel 3.3 LM2672LDX-3.3 S0002B 4500 Units on Tape and Reel 5.0 LM2672LD-5.0 S0003B 1000 Units on Tape and Reel 5.0 LM2672LDX-5.0 S0003B 4500 Units on Tape and Reel ADJ LM2672LD-ADJ S0004B 1000 Units on Tape and Reel ADJ LM2672LDX-ADJ S0004B 4500 Units on Tape and Reel SO-8 12 LM2672M-12 LM2672M-12 Shipped in Anti-Static Rails 12 LM2672MX-12 LM2672M-12 2500 Units on Tape and Reel 3.3 LM2672M-3.3 LM2672M-3.3 Shipped in Anti-Static Rails 3.3 LM2672MX-3.3 LM2672M-3.3 2500 Units on Tape and Reel 5.0 LM2672M-5.0 LM2672M-5.0 Shipped in Anti-Static Rails 5.0 LM2672MX-5.0 LM2672M-5.0 2500 Units on Tape and Reel ADJ LM2672M-ADJ LM2672M-ADJ Shipped in Anti-Static Rails ADJ LM2672MX-ADJ LM2672M-ADJ 2500 Units on Tape and Reel DIP 12 LM2672N-12 LM2672N-12 Shipped in Anti-Static Rails 3.3 LM2672N-3.3 LM2672N-3.3 Shipped in Anti-Static Rails 5.0 LM2672N-5.0 LM2672N-5.0 Shipped in Anti-Static Rails ADJ LM2672N-ADJ LM2672N-ADJ Shipped in Anti-Static Rails LM2672 2 Copyright © 1999-2012, Texas Instruments Incorporated Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and specifications. Supply Voltage 45V ON/OFF Pin Voltage −0.1V ≤ VSH ≤ 6V Switch Voltage to Ground −1V Boost Pin Voltage VSW + 8V Feedback Pin Voltage −0.3V ≤ VFB ≤ 14V ESD Susceptibility Human Body Model (Note 2) 2 kV Power Dissipation Internally Limited Storage Temperature Range −65°C to +150°C Lead Temperature M Package Vapor Phase (60s) +215°C Infrared (15s) +220°C N Package (Soldering, 10s) +260°C Maximum Junction Temperature +150°C Operating Ratings Supply Voltage 6.5V to 40V Temperature Range −40°C ≤ TJ ≤ +125°C Electrical Characteristics LM2672-3.3 Specifications with standard type face are for TJ = 25°C, and those in bold type face apply over full Operating Temperature Range. Symbol Parameter Conditions Typical Min Max Units (Note 4) (Note 5) (Note 5) SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3) VOUT Output Voltage VIN = 8V to 40V, ILOAD = 20 mA to 1A 3.3 3.251/3.201 3.350/3.399 V VOUT Output Voltage VIN = 6.5V to 40V, ILOAD = 20 mA to 500 mA 3.3 3.251/3.201 3.350/3.399 V η Efficiency VIN = 12V, ILOAD = 1A 86 % LM2672-5.0 Symbol Parameter Conditions Typical Min Max Units (Note 4) (Note 5) (Note 5) SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3) VOUT Output Voltage VIN = 8V to 40V, ILOAD = 20 mA to 1A 5.0 4.925/4.850 5.075/5.150 V VOUT Output Voltage VIN = 6.5V to 40V, ILOAD = 20 mA to 500 mA 5.0 4.925/4.850 5.075/5.150 V η Efficiency VIN = 12V, ILOAD = 1A 90 % LM2672-12 Symbol Parameter Conditions Typical Min Max Units (Note 4) (Note 5) (Note 5) SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3) VOUT Output Voltage VIN = 15V to 40V, ILOAD = 20 mA to 1A 12 11.82/11.64 12.18/12.36 V η Efficiency VIN = 24V, ILOAD = 1A 94 % LM2672 Copyright © 1999-2012, Texas Instruments Incorporated 3 LM2672-ADJ Symbol Parameter Conditions Typ Min Max Units (Note 4) (Note 5) (Note 5) SYSTEM PARAMETERS Test Circuit Figure 3 (Note 3) VFB Feedback Voltage VIN = 8V to 40V, ILOAD = 20 mA to 1A 1.210 1.192/1.174 1.228/1.246 V VOUT Programmed for 5V (see Circuit of Figure 3) VFB Feedback Voltage VIN = 6.5V to 40V, ILOAD = 20 mA to 500 mA 1.210 1.192/1.174 1.228/1.246 V VOUT Programmed for 5V (see Circuit of Figure 3) η Efficiency VIN = 12V, ILOAD = 1A 90 % All Output Voltage Versions Specifications with standard type face are for TJ = 25°C, and those in bold type face apply over full Operating Temperature Range. Unless otherwise specified, VIN = 12V for the 3.3V, 5V, and Adjustable versions and VIN = 24V for the 12V version, and ILOAD = 100 mA. Symbol Parameters Conditions Typ Min Max Units DEVICE PARAMETERS IQ Quiescent Current VFEEDBACK = 8V 2.5 3.6 mA For 3.3V, 5.0V, and ADJ Versions VFEEDBACK = 15V 2.5 mA For 12V Versions ISTBY Standby Quiescent Current ON/OFF Pin = 0V 50 100/150 μA ICL Current Limit 1.55 1.25/1.2 2.1/2.2 A IL Output Leakage Current VIN = 40V, ON/OFF Pin = 0V 1 25 μA VSWITCH = 0V VSWITCH = −1V, ON/OFF Pin = 0V 6 15 mA RDS(ON) Switch On-Resistance ISWITCH = 1A 0.25 0.30/0.50 Ω fO Oscillator Frequency Measured at Switch Pin 260 225 275 kHz D Maximum Duty Cycle 95 % Minimum Duty Cycle 0 % IBIAS Feedback Bias VFEEDBACK = 1.3V 85 nA Current ADJ Version Only VS/D ON/OFF Pin 1.4 0.8 2.0 V Voltage Thesholds IS/D ON/OFF Pin Current ON/OFF Pin = 0V 20 7 37 μA FSYNC Synchronization Frequency VSYNC = 3.5V, 50% duty cycle 400 kHz VSYNC Synchronization Threshold Voltage 1.4 V VSS Soft-Start Voltage 0.63 0.53 0.73 V ISS Soft-Start Current 4.5 1.5 6.9 μA θJA Thermal Resistance N Package, Junction to Ambient (Note 6) 95 °C/W M Package, Junction to Ambient (Note 6) 105 Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but device parameter specifications may not be guaranteed under these conditions. For guaranteed specifications and test conditions, see the Electrical Characteristics. Note 2: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. Note 3: External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator performance. When the LM2672 is used as shown in Figure 2 and Figure 3 test circuits, system performance will be as specified by the system parameters section of the Electrical Characteristics. Note 4: Typical numbers are at 25°C and represent the most likely norm. LM2672 4 Copyright © 1999-2012, Texas Instruments Incorporated Note 5: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100% production tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). Note 6: Junction to ambient thermal resistance with approximately 1 square inch of printed circuit board copper surrounding the leads. Additional copper area will lower thermal resistance further. See Application Information section in the application note accompanying this datasheet and the thermal model in LM267X Made Simple version 6.0 software. The value θJ−A for the LLP (LD) package is specifically dependent on PCB trace area, trace material, and the number of layers and thermal vias. For improved thermal resistance and power dissipation for the LLP package, refer to Application Note AN-1187. LM2672 Copyright © 1999-2012, Texas Instruments Incorporated 5 Typical Performance Characteristics Normalized Output Voltage 1293403 Line Regulation 1293404 Efficiency 1293405 Drain-to-Source Resistance 1293406 Switch Current Limit 1293407 Operating Quiescent Current 1293408 LM2672 6 Copyright © 1999-2012, Texas Instruments Incorporated Standby Quiescent Current 1293409 ON/OFF Threshold Voltage 1293410 ON/OFF Pin Current (Sourcing) 1293411 Switching Frequency 1293412 Feedback Pin Bias Current 1293413   Peak Switch Current 1293414 LM2672 Copyright © 1999-2012, Texas Instruments Incorporated 7 Dropout Voltage—3.3V Option 1293415 Dropout Voltage—5.0V Option 1293416 Block Diagram 1293417 * Patent Number 5,514,947 † Patent Number 5,382,918 FIGURE 1. LM2672 8 Copyright © 1999-2012, Texas Instruments Incorporated Typical Performance Characteristics (Circuit of Figure 2) Continuous Mode Switching Waveforms VIN = 20V, VOUT = 5V, ILOAD = 1A L = 47 μH, COUT = 68 μF, COUTESR = 50 mΩ 1293418 A: VSW Pin Voltage, 10 V/div. B: Inductor Current, 0.5 A/div C: Output Ripple Voltage, 20 mV/div AC-Coupled Horizontal Time Base: 1 μs/div Discontinuous Mode Switching Waveforms VIN = 20V, VOUT = 5V, ILOAD = 300 mA L = 15 μH, COUT = 68 μF (2×), COUTESR = 25 mΩ 1293419 A: VSW Pin Voltage, 10 V/div. B: Inductor Current, 0.5 A/div C: Output Ripple Voltage, 20 mV/div AC-Coupled Horizontal Time Base: 1 μs/div Load Transient Response for Continuous Mode VIN = 20V, VOUT = 5V, ILOAD = 1A L = 47 μH, COUT = 68 μF, COUTESR = 50 mΩ 1293420 A: Output Voltage, 100 mV/div, AC-Coupled B: Load Current: 200 mA to 1A Load Pulse Horizontal Time Base: 50 μs/div Load Transient Response for Discontinuous Mode VIN = 20V, VOUT = 5V, L = 47 μH, COUT = 68 μF, COUTESR = 50 mΩ 1293421 A: Output Voltage, 100 mV/div, AC-Coupled B: Load Current: 100 mA to 300 mA Load Pulse Horizontal Time Base: 200 μs/div LM2672 Copyright © 1999-2012, Texas Instruments Incorporated 9 Test Circuit and Layout Guidelines 1293422 CIN - 22 μF, 50V Tantalum, Sprague “199D Series” COUT - 47 μF, 25V Tantalum, Sprague “595D Series” D1 - 3.3A, 50V Schottky Rectifier, IR 30WQ05F L1 - 68 μH Sumida #RCR110D-680L CB - 0.01 μF, 50V Ceramic FIGURE 2. Standard Test Circuits and Layout Guides Fixed Output Voltage Versions 1293423 CIN - 22 μF, 50V Tantalum, Sprague “199D Series” COUT - 47 μF, 25V Tantalum, Sprague “595D Series” D1 - 3.3A, 50V Schottky Rectifier, IR 30WQ05F L1 - 68 μH Sumida #RCR110D-680L R1 - 1.5 kΩ, 1% CB - 0.01 μF, 50V Ceramic For a 5V output, select R2 to be 4.75 kΩ, 1% where VREF = 1.21V Use a 1% resistor for best stability. FIGURE 3. Standard Test Circuits and Layout Guides Adjustable Output Voltage Versions LM2672 10 Copyright © 1999-2012, Texas Instruments Incorporated Applications Hints 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 1A, 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. Also, refer to the LM2670 data sheet for additional applications information. 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 the VSW pin cycles 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 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 guaranteed performance the input voltage must be in the range of 6.5V to 40V. For best performance of the power supply the VIN pin should always be bypassed with an input capacitor located close to this pin and GND. 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 0.01μF. 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 LM2672, it is recommended that a broad ground plane be used to minimize signal coupling through- out the circuit SYNC This input allows control of the switching clock frequency. If left open-circuited the regulator will be 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. It is recommended that the external TTL or CMOS compatible clock (between 0V and a level greater than 3V) be ac coupled to the SYNC pin through a 100pF capacitor and a 1KΩ 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. 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 (3.3V, 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 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. 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 0.8V will completely turn OFF the regulator. The current drain from the input supply when OFF is only 50μA. The ON/OFF input has an internal pull-up current source of approximately 20μA and a protection clamp zener diode of 7V to ground. When electrically driving the ON/OFF pin the high voltage level for the ON condition should not exceed the 6V absolute maximum limit. When ON/ OFF control is not required this pin should be left open. DAP (LLP PACKAGE) The Die Attach Pad (DAP) can and should be connected to the PCB Ground plane/island. For CAD and assembly guidelines refer to Application Note SNAO401 at http://www.ti.com/lit/an/snoa401q/snoa401q.pdf. LM2672 Copyright © 1999-2012, Texas Instruments Incorporated 11 LM2672 Series Buck Regulator Design Procedure (Fixed Output) PROCEDURE (Fixed Output Voltage Version) EXAMPLE (Fixed Output Voltage Version) To simplify the buck regulator design procedure, National Semiconductor is making available computer design software to be used with the SIMPLE SWITCHER line of switching regulators. LM267X Made Simple version 6.0 is available on Windows® 3.1, NT, or 95 operating systems. Given: Given: VOUT = Regulated Output Voltage (3.3V, 5V, or 12V) VOUT = 5V VIN(max) = Maximum DC Input Voltage VIN(max) = 12V ILOAD(max) = Maximum Load Current ILOAD(max) = 1A 1. Inductor Selection (L1) A. Select the correct inductor value selection guide from Figure 4 and Figure 5 or Figure 6 (output voltages of 3.3V, 5V, or 12V respectively). For all other voltages, see the design procedure for the adjustable version. 1. Inductor Selection (L1) A. Use the inductor selection guide for the 5V version shown in Figure 5. B. From the inductor value selection guide, identify the inductance region intersected by the Maximum Input Voltage line and the Maximum Load Current line. Each region is identified by an inductance value and an inductor code (LXX). B. From the inductor value selection guide shown in Figure 5, the inductance region intersected by the 12V horizontal line and the 1A vertical line is 33 μH, and the inductor code is L23. C. Select an appropriate inductor from the four manufacturer's part numbers listed in Figure 8. Each manufacturer makes a different style of inductor to allow flexibility in meeting various design requirements. Listed below ar