National Semiconductor | High-performance Analog

 

 LM3477   

High Efficiency High-Side N-Channel Controller for Switching Regulator
Click link to Download

Features
  • 500kHz switching frequency
  • Adjustable current limit
  • 1.5% reference
  • Thermal shutdown
  • Frequency compensation optimized with a single capacitor and resistor
  • Internal softstart
  • Current mode operation
  • Undervoltage lockout with hysteresis
  • 8-lead Mini-SO8 (MSOP-8) package
  • Description

    The LM3477/A is a high-side N-channel MOSFET switching regulator controller. It can be used in topologies requiring a high side MOSFET such as buck, inverting (buck-boost) and zeta regulators. The LM3477/A's internal push pull driver allows compatibility with a wide range of MOSFETs. This, the wide input voltage range, use of discrete power components and adjustable current limit allows the LM3477/A to be optimized for a wide variety of applications.

    The LM3477/A uses a high switching frequency of 500kHz to reduce the overall solution size. Current-mode control requires only a single resistor and capacitor for frequency compensation. The current mode architecture also yields superior line and load regulation and cycle-by-cycle current limiting. A 5µA shutdown state can be used for power savings and for power supply sequencing. Other features include internal soft-start and output over voltage protection. The internal soft-start reduces inrush current. Over voltage protection is a safety feature to ensure that the output voltage stays within regulation.

    The LM3477A is similar to the LM3477. The primary difference between the two is the point at which the device transitions into hysteretic mode. The hysteretic threshold of the LM3477A is one-third of the LM3477.


    Applications

    • Local Voltage Regulation
    • Distributed Power
    • Notebook and Palmtop Computers
    • Internet Appliances
    • Printers and Office Automation
    • Battery operated Devices
    • Cable Modems
    • Battery Chargers
     Hysteretic Threshold
    LM3477[Approximately_Equals] 36% of programmed current limit
    LM3477A[Approximately_Equals] 12% of programmed current limit

    Also Recommended
    LM1770Low-Voltage SOT-23 Synchronous Buck Controller
    LM2642Dual, Multiphase, Buck Switching Controller
    LM2727Synchronous, Low Voltage, 2MHz, Buck Controller
    LM2636Digitally Controlled, 1MHz, Buck Controller
    LM3075Synchronous, Medium Voltage, Buck Controller



    Typical Application
    click for larger image


    Block Diagram
    click for larger image



    Typical Performance
    *click for larger image


    Parameters / ValuesLM3477 LM1770 LM2642 LM2727 LM2636 LM3075
    Output Current6000 mA 4000 mA 20000 mA 20000 mA
    Input Min Voltage2.95 Volt 2.8 Volt 4.5 Volt 2.2 Volt
    Input Max Voltage35 Volt 5.5 Volt 30 Volt 16 Volt
    Output Range1.265V min 0.8V to 4.5V 1.238V-27V (each output) 0.6V to 13.5V
    Frequency Min500 kHz 300 kHz 300 kHz 50 kHz
    Frequency Max500 kHz 1000 kHz 300 kHz 2000 kHz
    Feedback Voltage1.265 Volt 0.8 Volt 1.238 Volt 0.6 Volt
    Feedback Tolerance1.5 % 2 % 2 % 1.5 %
    Adj Switch FrequencyNo No No Yes
    Adjustable OutputYes Yes Yes Yes
    Synchronous RectificationNo Yes Yes
    On/Off PinYes No Yes Yes
    PowerGood / Error FlagNo No Yes Yes
    SoftStartYes Yes Yes Yes
    Sync PinNo No No No
    InvertingYes Yes No No
    FlybackNo No No No
    Lossless Current SenseNo No Yes Yes
    RegTypeSwitching Controller Switching Controller Switching Controller Switching Controller
    Temperature Min-40 deg C -40 deg C -40 deg C 0 deg C
    Temperature Max125 deg C 125 deg C 125 deg C 125 deg C
    Channels1 Channels 1 Channels 2 Channels 1 Channels
    Special FeaturesHysteretic threshold at 36% of programmed current limit; Vout OVP No compensation required 180deg out-of-phase channels; Individual softstart allows sequencing UVLO; UVP; Suspend to disk shutdown
    TopologyBuck Buck Buck Synchronous Buck
    PWM ModeCurrent Constant on-time Current Voltage
    Step-DownYes No Yes Yes
    Step-UpNo No No No
    Output Min1.265 Volt 0.8 Volt 1.238 Volt 0.6 Volt

    Datasheets
    TitleSizeDateOther
    Language
    LM3477 High Efficiency High-Side N-Channel Controller for Switching Regulator841
    Kbytes
    20-Jul-04日本語  


    Application Notes
    TitleSizeDateOther
    Language
    AN-1193: Application Note 1193 Layout Guidelines for Switching Power Supplies248
    Kbytes
    10-May-04 

    Part Number(s)
    (NSID)
    Top ViewAvailabilityCurrent Reported StockBudgetary PricingPack
    Size
    LM3477AMM/NOPB

    LM3477AMM

    RoHS Status


    MINI SOIC
    Full production
    Lead Time: 6 weeks

    Samples
    DistributorRegionQty
    ARROWWorldwide5430
    AVNET-EMWorldwide1000
    DIGI-KEYWorldwide2431
    FARNELLEurope and Asia482
    MOUSERWorldwide1000
    NEWARKAmericas265
    RS COMPONENTSWorldwide525
    TAYLORAmericas5430
    $0.92 each at 1K+ pcsreel
    of
    1000
    LM3477AMMX/NOPB

    LM3477AMMX

    RoHS Status


    MINI SOIC
    Full production
    Lead Time: 8 weeks

     
    DistributorRegionQty
    AVNET-EMWorldwide3500
    DIGI-KEYWorldwide0
    $0.92 each at 1K+ pcsreel
    of
    3500
    LM3477MM/NOPB

    LM3477MM

    RoHS Status


    MINI SOIC
    Full production
    Lead Time: 6 weeks

    Samples
    DistributorRegionQty
    ARROWWorldwide14300
    AVNET-EMWorldwide1000
    DIGI-KEYWorldwide3373
    FARNELLEurope and Asia2065
    MOUSERWorldwide975
    RS COMPONENTSWorldwide953
    TAYLORAmericas14300
    $0.92 each at 1K+ pcsreel
    of
    1000
    LM3477MMX/NOPB

    LM3477MMX

    RoHS Status


    MINI SOIC
    Full production
    Lead Time: 8 weeks

     
    DistributorRegionQty
    AVNET-EMWorldwide3500
    DIGI-KEYWorldwide0
    $0.92 each at 1K+ pcsreel
    of
    3500

    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 LM3477.

    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 LM3477 is located at RoHS Status.

    Part Number(s)
    (NSID)
    DescriptionAvailabilityCurrent Reported StockBudgetary PricingPack
    Size
    LM3477EVAL
    High Efficiency High-Side N-Channel Controller for Switching RegulatorFull production


     
    DistributorRegionQty
    DIGI-KEYWorldwide0
    MOUSERWorldwide2
    $30.00 each1

    Features:

    • 8-lead Mini-SO8 (MSOP-8) package
    • Internal push-pull driver with 1A peak current capability
    • Low current hysteric mode improves light load efficiency
    • Current limit and thermal shutdown
    • Frequency compensation optimized with a capacitor and resistor
    • Internal softstart
    • Current mode operation
    • Undervoltage lockout with hystersis

    Contents:

    • A fully assembled LM3477 Evaluation Board
    • Application note for LM3477
    • Datasheet for LM3477/78/88
    • Simple Switcher selection guide



    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
    LM3477AMM/NOPB

    LM3477AMM
    29.851
    30.002
    MINI SOIC81
    1
    260
    260
    DetailDownloadN/A
    ZXTT
    S13A
    LM3477AMMX/NOPB

    LM3477AMMX
    29.851
    30.002
    MINI SOIC81
    1
    260
    260
    DetailDownloadN/A
    ZXTT
    S13A
    LM3477MM/NOPB

    LM3477MM
    29.851
    30.002
    MINI SOIC81
    1
    260
    260
    DetailDownloadN/A
    ZXTT
    S13B
    LM3477MMX/NOPB

    LM3477MMX
    29.851
    30.002
    MINI SOIC81
    1
    260
    260
    DetailDownloadN/A
    ZXTT
    S13B

    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 LM3477.

    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 LM3477 is located at RoHS Status.

    CAD Symbols and Models
    Download LM3477 CAD Symbols
     Models
    N/A


    Reliability Metrics
    Part Number Process EFR Reject EFR Sample Size PPM LTA Rejects LTA Device Hours FITS MTTF (Hours)
    LM3477AMMABCD15004268000639400011814314958
    LM3477AMMXABCD15004268000639400011814314958
    LM3477MMABCD15004268000639400011814314958
    LM3477MMXABCD15004268000639400011814314958

    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 LM3477.

    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 LM3477 is located at RoHS Status.

    [Information as of 9-Feb-2012]