National Semiconductor | High-performance Analog

 

 LM1770   
Low-Voltage SOT23 Synchronous Buck Controller With No External Compensation from the PowerWise® Family		 Click link to Download

Features
  • Input voltage range of 2.8V to 5.5V
  • 0.8V reference voltage
  • No compensation required
  • Constant frequency across input range
  • Low quiescent current of 400µA
  • Internal soft-start
  • Short circuit protection
  • Tiny SOT-23 package

    • Description

    The LM1770 is an efficient synchronous buck switching controller in a tiny SOT23 package. The constant on-time control scheme provides a simple design free of compensation components, allowing minimal component count and board space. It also incorporates a unique input feed-forward to maintain a constant frequency independent of the input voltage. The LM1770 is optimized for a low voltage input range of 2.8V to 5.5V and can provide an adjustable output as low as 0.8V. Driving an external high side PFET and low side NFET it can provide efficiencies as high as 95%.

    Three versions of the LM1770 are available depending on the switching frequency desired for the application. Nominal switching frequencies are in the range of 100kHz to 1000kHz.


    Applications

  • Simple To Design, High Efficiency Step Down Switching Regulators
  • Set-Top Boxes
  • Cable Modems
  • Printers
  • Digital Video Recorders
  • Servers

    • Also Recommended
    LM1771▲With Precision Enable
    LM2853▲3A Integrated FETs PWM Version



    Typical Application
    click for larger image


    		Block Diagram
    click for larger image



    Typical Performance
    *click for larger image


    Parameters / ValuesLM1770 LM1771 LM2853
    Output Current4000 mA 6000 mA 3000 mA
    Input Min Voltage2.8 Volt 2.8 Volt 3 Volt
    Input Max Voltage5.5 Volt 5.5 Volt 5.5 Volt
    Feedback Voltage0.8 Volt 0.8 Volt Undefined Volt
    Feedback Tolerance2 % 2 %
    Frequency Min300 kHz 300 kHz 550 kHz
    Frequency Max1000 kHz 1000 kHz 550 kHz
    Efficiency (peak)95 % 95 % 95 %
    Output Range0.8V to 4.5V 0.8V to 4.5V 1.8, 1, 2.5, 1.2, 0.8, 3.3, 3, 1.5
    Adj Switch FrequencyNo No No
    Adjustable OutputYes Yes No
    Synchronous RectificationYes Yes Yes
    On/Off PinNo Yes Yes
    PowerGood / Error FlagNo No No
    SoftStartYes Yes Yes
    Sync PinNo No No
    InvertingYes No No
    FlybackNo No No
    Lossless Current SenseNo No
    RegTypeSwitching Controller Switching Controller Switching Regulator
    Temperature Min-40 deg C -40 deg C -40 deg C
    Temperature Max125 deg C 125 deg C 125 deg C
    Channels1 Channels 1 Channels
    Special FeaturesNo compensation required Precision enable for sequencing multiple rails Internal compensation, low standby current
    TopologyBuck Buck Synchronous Buck
    PWM ModeConstant on-time Constant on-time Voltage Mode Control
    Step-DownNo Yes Yes
    Step-UpNo No
    Output Max4.5 Volt 4.5 Volt 1.8, 1, 2.5, 1.2, 0.8, 3.3, 3, 1.5 Volt
    Output Min0.8 Volt 0.8 Volt 1.8, 1, 2.5, 1.2, 0.8, 3.3, 3, 1.5 Volt
    PowerWiseYes Yes Yes

    Datasheets
    TitleSizeDateOther
    Language
    LM1770 Low-Voltage SOT23 Synchronous Buck Controller With No External Compensation687
    Kbytes    		20-Jul-06日本語  


    Application Notes
    TitleSizeDateOther
    Language
    AN-1400: Application Note 1400 LM1770 Evaluation Board528
    Kbytes    		30-Sep-05 中文
    AN-1414: Application Note 1414 LM1770 Design Reference750
    Kbytes    		8-Nov-05 中文
    AN-1481: Application Note 1481 Controlling Output Ripple and Achieving ESR Independence in Constant On-Time (COT) Regulator Designs574
    Kbytes    		27-Sep-06日本語
    中文


    Other Technical Documents
    TitleTypeDate
    Advanced Topics in Powering FPGAsPower Designer 2007-03-22

    Part Number(s)
    (NSID)    		Top ViewAvailabilityCurrent Reported StockBudgetary PricingPack
    Size
    LM1770SMF/NOPB


    RoHS Status

    SOT-23    		Full production
    Lead Time: 6 weeks

     
    DistributorRegionQty
    ARROWWorldwide1000
    DIGI-KEYWorldwide2323
    MOUSERWorldwide1000
    RS COMPONENTSWorldwide75
    TAYLORAmericas1000
    		$0.80 each at 1K+ pcsreel
    of
    1000
    LM1770SMFX/NOPB


    RoHS Status

    SOT-23    		Full production
    Lead Time: 6 weeks

     
    DistributorRegionQty
    DIGI-KEYWorldwide0
    		$0.80 each at 1K+ pcsreel
    of
    3000
    LM1770TMF/NOPB


    RoHS Status

    SOT-23    		Full production
    Lead Time: 6 weeks

    Samples
    DistributorRegionQty
    ARROWWorldwide1000
    DIGI-KEYWorldwide2016
    MOUSERWorldwide965
    RS COMPONENTSWorldwide75
    TAYLORAmericas1000
    		$0.80 each at 1K+ pcsreel
    of
    1000
    LM1770TMFX/NOPB


    RoHS Status

    SOT-23    		Full production
    Lead Time: 6 weeks

     
    DistributorRegionQty
    DIGI-KEYWorldwide0
    		$0.80 each at 1K+ pcsreel
    of
    3000
    LM1770UMF/NOPB


    RoHS Status

    SOT-23    		Full production
    Lead Time: 6 weeks

    Samples
    DistributorRegionQty
    ARROWWorldwide2000
    DIGI-KEYWorldwide1758
    FARNELLEurope and Asia589
    MOUSERWorldwide1000
    RS COMPONENTSWorldwide70
    TAYLORAmericas2000
    		$0.80 each at 1K+ pcsreel
    of
    1000
    LM1770UMFX/NOPB


    RoHS Status

    SOT-23    		Full production
    Lead Time: 6 weeks

     
    DistributorRegionQty
    DIGI-KEYWorldwide0
    		$0.80 each at 1K+ pcsreel
    of
    3000

    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 LM1770.

    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 LM1770 is located at RoHS Status.

    Part Number(s)
    (NSID)    		DescriptionAvailabilityCurrent Reported StockBudgetary PricingPack
    Size
    LM1770EVAL
    		Low-Voltage SOT23 Synchronous Buck Controller With No External CompensationFull production


     
    DistributorRegionQty
    DIGI-KEYWorldwide0
    		$28.00 each1

    Desscription:

    LM1770 SOT-23 Synchronous Buck Controller

    Features:

    • Input voltage range of 2.8V to 5.5V
    • 0.8V reference voltage
    • No compensation required
    • Constant frequency across input range
    • Low quiescent current of 400mA
    • Internal soft-start
    • Short circuit protection
    • Tiny SOT-23 package

    Contents:

    • A fully assembled LM1770 evaluation board
    • LM1770 datasheet
    • LM1770 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
    LM1770SMF/NOPB

    		14.696
    14.801
    		SOT-2351260DetailDownloadN/A
    		SKJB
    XTT
    LM1770SMFX/NOPB

    		14.696
    14.801
    		SOT-2351260DetailDownloadN/A
    		SKJB
    XTT
    LM1770TMF/NOPB

    		14.696
    14.801
    		SOT-2351260DetailDownloadN/A
    		SKKB
    XTT
    LM1770TMFX/NOPB

    		14.696
    14.801
    		SOT-2351260DetailDownloadN/A
    		SKKB
    XTT
    LM1770UMF/NOPB

    		14.696
    14.801
    		SOT-2351260DetailDownloadN/A
    		SKLB
    XTT
    LM1770UMFX/NOPB

    		14.696
    14.801
    		SOT-2351260DetailDownloadN/A
    		SKLB
    XTT

    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 LM1770.

    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 LM1770 is located at RoHS Status.

    CAD Symbols and Models
    Download LM1770 CAD Symbols
    		 Models
    N/A


    Reliability Metrics
    Part Number Process EFR Reject EFR Sample Size PPM LTA Rejects LTA Device Hours FITS MTTF (Hours)
    LM1770SMFCS065247473430552700011568301341
    LM1770SMFXCS065247473430552700011568301341
    LM1770TMFCS065247473430552700011568301341
    LM1770TMFXCS065247473430552700011568301341
    LM1770UMFCS065247473430552700011568301341
    LM1770UMFXCS065247473430552700011568301341

    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 LM1770.

    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 LM1770 is located at RoHS Status.

    [Information as of 9-Feb-2012]
    Copyright © 2011 National Semiconductor Corporation