SLUSB41A July   2012  – December 2014 UCC28700 , UCC28701 , UCC28702 , UCC28703


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Device Comparison Table
  6. Pin Configuration and Functions
  7. Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Switching Characteristics
    7. 7.7 Typical Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Detailed Pin Description
        1. VDD (Device Bias Voltage Supply)
        2. GND (Ground)
        3. VS (Voltage-Sense)
        4. DRV (Gate Drive)
        5. CS (Current Sense)
        6. CBC (Cable Compensation), Pin 1 UCC28700
        7. NTC (NTC Thermistor Shut-down), Pin 1 UCC28701/2/3
      2. 8.3.2 Fault Protection
    4. 8.4 Device Functional Modes
      1. 8.4.1 Primary-Side Voltage Regulation
      2. 8.4.2 Primary-Side Current Regulation
      3. 8.4.3 Valley-Switching
      4. 8.4.4 Start-Up Operation
  9. Applications and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. Transformer Parameter Verification
        2. Output Capacitance
        3. VDD Capacitance, CDD
        4. VDD Start-Up Resistance, RSTR
        5. VS Resistor Divider, Line Compensation, and Cable Compensation
        6. Input Bulk Capacitance and Minimum Bulk Voltage
        7. Transformer Turns Ratio, Inductance, Primary-Peak Current
        8. Standby Power Estimate
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Device Nomenclature
        1.  Capacitance Terms in Farads
        2.  Duty Cycle Terms
        3.  Frequency Terms in Hertz
        4.  Current Terms in Amperes
        5.  Current and Voltage Scaling Terms
        6.  Transformer Terms
        7.  Power Terms in Watts
        8.  Resistance Terms in Ω
        9.  Timing Terms in Seconds
        10. Voltage Terms in Volts
        11. AC Voltage Terms in VRMS
        12. Efficiency Terms
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
      2. 12.2.2 Related Links
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

12 Device and Documentation Support

12.1 Device Support

12.1.1 Device Nomenclature Capacitance Terms in Farads

    CBULKtotal input capacitance of CB1 and CB2.
    CDDminimum required capacitance on the VDD pin.
    COUTminimum output capacitance required. Duty Cycle Terms

    DMAGCCsecondary diode conduction duty cycle in CC, 0.425.
    DMAXMOSFET on-time duty cycle. Frequency Terms in Hertz

    fLINEminimum line frequency.
    fMAXtarget full-load maximum switching frequency of the converter.
    fMINminimum switching frequency of the converter, add 15% margin over the fSW(min) limit of the device. Current Terms in Amperes

    IOCCconverter output constant-current target.
    IPP(max)maximum transformer primary current.
    ITRANrequired positive load-step current. Current and Voltage Scaling Terms Transformer Terms

    LPtransformer primary inductance.
    NAStransformer auxiliary-to-secondary turns ratio.
    NPAtransformer primary-to-auxiliary turns ratio.
    NPStransformer primary-to-secondary turns ratio. Power Terms in Watts

    PINconverter maximum input power.
    POUTfull-load output power of the converter.
    PRSTRVDD start-up resistor power dissipation.
    PSBtotal stand-by power.
    PSB_CONVPSB minus start-up resistor and snubber losses. Resistance Terms in Ω

    RCSprimary current programming resistance
    RESRtotal ESR of the output capacitor(s).
    RPLpreload resistance on the output of the converter.
    RS1high-side VS pin resistance.
    RS2low-side VS pin resistance.
    RSTRmaximum start-up resistance to achieve the turn-on time target.
    RSTRVDD start-up resistance. Timing Terms in Seconds

    TDcurrent-sense delay including MOSFET turn-off delay; add 50 ns to MOSFET delay.
    TDMAG(min)minimum secondary rectifier conduction time.
    TON(min)minimum MOSFET on time.
    TRresonant frequency during the DCM (discontinuous conduction mode) time.
    TSTRconverter start-up time requirement. Voltage Terms in Volts

    VBLKhighest bulk capacitor voltage for stand-by power measurement.
    VBULK(min)minimum voltage on CB1 and CB2 at full power.
    VOCBCtarget cable compensation voltage at the output terminals.
    Voutput voltage drop allowed during the load-step transient.
    VDSPKpeak MOSFET drain-to-source voltage at high line.
    VFsecondary rectifier forward voltage drop at near-zero current.
    VFAauxiliary rectifier forward voltage drop.
    VLKestimated leakage inductance energy reset voltage.
    VOCVregulated output voltage of the converter.
    VOCCtarget lowest converter output voltage in constant-current regulation.
    VREVpeak reverse voltage on the secondary rectifier.
    VRIPPLEoutput peak-to-peak ripple voltage at full-load. AC Voltage Terms in VRMS

    VIN(max)maximum input voltage to the converter.
    VIN(min)minimum input voltage to the converter.
    VIN(run)converter input start-up (run) voltage. Efficiency Terms

    ηSBestimated efficiency of the converter at no-load condition, not including start-up resistance or bias losses. For a 5-V USB charger application, 60% to 65% is a good initial estimate.
    ηconverter overall efficiency.
    ηXFMRtransformer primary-to-secondary power transfer efficiency.

12.2 Documentation Support

12.2.1 Related Documentation

For related documentation see the following:

    Using the UCC28700EVM-068, Evaluation Module, SLUU968

12.2.2 Related Links

The table below lists quick access links. Categories include technical documents, support and community resources, tools and software, and quick access to sample or buy.

Table 2. Related Links

UCC28700 Click here Click here Click here Click here Click here
UCC28701 Click here Click here Click here Click here Click here
UCC28702 Click here Click here Click here Click here Click here
UCC28703 Click here Click here Click here Click here Click here

12.3 Trademarks

All other trademarks are the property of their respective owners.

12.4 Electrostatic Discharge Caution


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.

12.5 Glossary

SLYZ022TI Glossary.

This glossary lists and explains terms, acronyms, and definitions.