National Semiconductor | High-performance Analog

 

 LM2747   

Synchronous Buck Controller with Pre-bias Startup, and Optional Clock Synchronization from the PowerWise® Family
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Features

  • ±1% feedback voltage accuracy over temperature
  • Switching frequency from 50 kHz to 1 MHz
  • Switching frequency synchronize range 250 kHz to 1 MHz
  • Startup with a pre-biased output load
  • Power stage input voltage from 1V to 14V
  • Control stage input voltage from 3V to 6V
  • Output voltage adjustable down to 0.6V
  • Power Good flag and shutdown
  • Output overvoltage and undervoltage detection
  • Low-side adjustable current sensing
  • Adjustable soft-start
  • Tracking and sequencing with shutdown and soft start pins
  • TSSOP-14 package
  • Description

    The LM2747 is a high-speed synchronous buck regulator controller with a feedback voltage accuracy of ±1%. It can provide simple down conversion to output voltages as low as 0.6V. Though the control section of the IC is rated for 3 to 6V, the driver section is designed to accept input supply rails as high as 14V. The use of adaptive non-overlapping MOSFET gate drivers helps avoid potential shoot-through problems while maintaining high efficiency. The IC is designed for the more cost-effective option of driving only N-channel MOSFETs in both the high-side and low-side positions. It senses the low-side switch voltage drop for providing a simple, adjustable current limit.

    The LM2747 features a fixed-frequency voltage-mode PWM control architecture which is adjustable from 50 kHz to 1 MHz with one external resistor. In addition, the LM2747 also allows the switching frequency to be synchronized to an external clock signal over the range of 250 kHz to 1 MHz. This wide range of switching frequency gives the power supply designer the flexibility to make better tradeoffs between component size, cost and efficiency.

    Features include the ability to startup with a pre-biased load on the output, soft-start, input undervoltage lockout (UVLO) and Power Good (based on both undervoltage and overvoltage detection). In addition, the shutdown pin of the IC can be used for providing startup delay, and the soft-start pin can be used for implementing precise tracking, for the purpose of sequencing with respect to an external rail.


    Applications

  • Down Conversion from 3.3V
  • Cable Modem, DSL and ADSL
  • Laser Jet and Ink Jet Printers
  • Low Voltage Power Modules
  • DSP, ASIC, Core and I/O
  • Also Recommended
    LM2743Synchronous Buck Controller With Tracking And Soft-Start
    LM2745+/- 1.5% Accuracy
    LM3743Low-Voltage Synchronous Buck Controller In MSOP-10



    Typical Application
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    Block Diagram
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    Typical Performance
    click for larger image


    Parameters / ValuesLM2747 LM2743 LM2745 LM3743
    Output Current20000 mA 20000 mA 20000 mA 10000 mA
    Input Min Voltage1 Volt 1 Volt 1 Volt 3 Volt
    Input Max Voltage17 Volt 16 Volt 17 Volt 5.5 Volt
    Feedback Voltage0.6 Volt 0.6 Volt 0.6 Volt 0.8 Volt
    Feedback Tolerance1 % 1.5 % 1.75 %
    Frequency Min50 kHz 50 kHz 50 kHz 300 kHz
    Frequency Max1000 kHz 2000 kHz 1000 kHz 1000 kHz
    Efficiency (peak)85 % 85 % 85 % 95 %
    Output Range0.6V to 13.5V 0.6V to 13.5V 0.6V to 13.5V 0.8V to 4.6V
    Adj Switch FrequencyYes Yes Yes No
    Adjustable OutputYes Yes Yes Yes
    On/Off PinYes Yes Yes Yes
    PowerGood / Error FlagYes Yes Yes No
    SoftStartYes Yes Yes Yes
    Sync PinYes No Yes No
    InvertingNo No No No
    FlybackNo No No No
    Lossless Current SenseYes Yes Yes Yes
    RegTypeSwitching Controller Switching Controller Switching Controller Switching Regulator
    Temperature Min-40 deg C -40 deg C -40 deg C -40 deg C
    Temperature Max125 deg C 125 deg C 125 deg C 125 deg C
    Channels1 Channels 1 Channels 1 Channels 1 Channels
    Special FeaturesPre-bias startup; 40ns min on-time 2.7V UVLO; Tri-State output during SD; Tracking; Precision SD threshold Pre-bias startup; 40ns min on-time Pre-bias start-up; Hiccup mode; External programmable soft-start and tracking
    TopologyBuck Buck Buck Buck
    PWM ModeVoltage Voltage Voltage Voltage
    Step-DownYes Yes Yes Yes
    Step-UpNo No No No
    Output PowerUndefined Watt Undefined Watt Undefined Watt Undefined Watt
    Output Max13.5 Volt 13.5 Volt 13.5 Volt 4.6 Volt
    Output Min0.6 Volt 0.6 Volt 0.6 Volt 0.8 Volt
    PowerWiseYes Yes Yes Yes
    Part Number(s)
    (NSID)
    Top ViewAvailabilityCurrent Reported StockBudgetary PricingPack
    Size
    LM2747MTC/NOPB

    LM2747MTC

    RoHS Status


    TSSOP
    Full production
    Lead Time: 6 weeks

     
    DistributorRegionQty
    ARROWWorldwide221
    DIGI-KEYWorldwide102
    MOUSERWorldwide282
    RS COMPONENTSWorldwide13
    TAYLORAmericas221
    $1.45 each at 1K+ pcsrail
    of
    94
    LM2747MTCX/NOPB

    LM2747MTCX

    RoHS Status


    TSSOP
    Full production
    Lead Time: 6 weeks

     
    DistributorRegionQty
    CEACAsia Pacific20000
    DIGI-KEYWorldwide0
    $1.45 each at 1K+ pcsreel
    of
    2500

    All information pertaining to the RoHS Compliance Standard can be found at http://www.national.com/en/packaging/leadfree.html.

    Moisture Sensitivity Level Data for LM2747.

    A RoHS compliance or an IPC 1752 report can be acquired at http://www.national.com/en/packaging/greennopb.html.

    National's certificate of product compliance for LM2747 is located at RoHS Status.

    Part Number(s)
    (NSID)
    DescriptionAvailabilityCurrent Reported StockBudgetary PricingPack
    Size
    LM2747-19AEVAL
    LM2747 Synchronous Buck Controller with Pre-bias Startup, and Optional Clock SynchronizationFull production


     
    DistributorRegionQty
    DIGI-KEYWorldwide0
    $65.30 each1

    Features:

    • ± feedback voltage accuracy over temperature
    • Switching frequency from 50 kHz to 1 MHz
    • Switching frequency synchronize range 250 kHz to 1 MHz
    • Startup with a pre-biased output load
    • Power stage input voltage from 1V to 14V
    • Control stage input voltage from 3V to 6V
    • Output voltage adjustable down to 0.6V
    • Power Good flag and shutdown
    • Output overvoltage and undervoltage detection
    • Low-side adjustable current sensing
    • Adjustable soft-start
    • Tracking and sequencing with shutdown and soft-start pins
    • TSSOP-14 package

    Applications:

    • Down Conversion from 3.3V
    • Cable Modem, DSL and ADSL
    • Laser Jet and Ink Jet Printers
    • Low Voltage Power Modules
    • DSP, ASIC, Core and I/O

    Contents:

    • A LM2747-19A Fully Assembled Evaluation Board
    • A LM2747 Datasheet
    • A LM2747 Evaluation Board Appnote

    Part Number(s)
    (NSID)
    DescriptionAvailabilityCurrent Reported StockBudgetary PricingPack
    Size
    LM2747EVAL
    Synchronous Buck Controller with Pre-bias Startup, and Optional Clock SynchronizationFull production


     
    DistributorRegionQty
    DIGI-KEYWorldwide0
    $65.30 each1

    Description:

    LM2747 Synchronous Buck Controller with Pre-bias Start-up, and Optional Clock Synchronization

    Features:

    • ±1% feedback voltage accuracy over temperature
    • Switching frequency synchronize range 250 kHz to 1MHz
    • Startup with a pre-biased output load
    • Power stage input voltage from 1V to 14V
    • Control stage input voltage from 3V to 6V
    • Output voltage adjustable down to 0.6V
    • Power Good flag and shutdonwn
    • Output overvoltage and undervoltage detection
    • Low-side adjustable current sensing
    • Adjustable soft-start
    • Tracking and sequencing with shutdown and soft start pins
    • TSSOP-14 package

    Applications:

    • Down Conversion from 3.3V
    • Cable Modem, DSL, and ADSL
    • Laser Jet and Ink Jet Printers
    • Low Voltage Power Modules
    • DSP, ASIC, Core and I/O

    Contents:

    • A fully assembled LM2747 evaluation board
    • LM2747 datasheet
    • LM2747 evaluation board appnote



    National Semiconductor follows the provisions of the Product Stewardship Guide for Customers (CSP-9-111C1) and Banned Substances and Materials of Interest Specification (CSP-9-111S2) for regulatory environmental compliance. Details may be found at: www.national.com/en/packaging/greennopb.html. Lead free products are RoHS compliant.

    Lead Free product status is available through the search tool located here

    Part Number(s)
    (NSID)
    Weight
    (milligrams)
    TypePinsMSL RatingPeak ReflowRoHS
    Status
    CAD SymbolsModelsPackage
    Marking
    Format
    LM2747MTC/NOPB

    LM2747MTC
    53.783
    54.004
    TSSOP141
    1
    260
    260
    DetailDownloadN/A
    NSUZXYTT
    2747
    MTC
    LM2747MTCX/NOPB

    LM2747MTCX
    53.783
    54.004
    TSSOP141
    1
    260
    260
    DetailDownloadN/A
    NSUZXYTT
    2747
    MTC

    All information pertaining to the RoHS Compliance Standard can be found at http://www.national.com/en/packaging/leadfree.html.

    Moisture Sensitivity Level Data for LM2747.

    A RoHS compliance or an IPC 1752 report can be acquired at http://www.national.com/en/packaging/greennopb.html.

    National's certificate of product compliance for LM2747 is located at RoHS Status.

    Design Tools
    TitleSizeDate
    Article - Exploit Controller Features to Optimize Power Designs  

    CAD Symbols and Models
    Download LM2747 CAD Symbols
     Models
    N/A


    Reliability Metrics
    Part Number Process EFR Reject EFR Sample Size PPM LTA Rejects LTA Device Hours FITS MTTF (Hours)
    LM2747MTCABCD15004268000639400011814314958
    LM2747MTCXABCD15004268000639400011814314958

    Note: The Early Failure Rates (EFR) were calculated as point estimate PPM based on rejects and sample size for EFR. The Long Term Failure Rates were calculated at 60% confidence using the Arrhenius equation at 0.7eV activation energy and derating the assumed stress temperature of 150°C to an application temperature of 55°C.

    For more information on Reliability Metrics, please click here.


    All information pertaining to the RoHS Compliance Standard can be found at http://www.national.com/en/packaging/leadfree.html.

    Moisture Sensitivity Level Data for LM2747.

    A RoHS compliance or an IPC 1752 report can be acquired at http://www.national.com/en/packaging/greennopb.html.

    National's certificate of product compliance for LM2747 is located at RoHS Status.

    [Information as of 9-Feb-2012]