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  • UCC2870x Constant-Voltage, Constant-Current Controller With Primary-Side Regulation

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

      PRODUCTION DATA.  

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  • UCC2870x Constant-Voltage, Constant-Current Controller With Primary-Side Regulation
  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 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. 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. 8.3.1.1 VDD (Device Bias Voltage Supply)
        2. 8.3.1.2 GND (Ground)
        3. 8.3.1.3 VS (Voltage-Sense)
        4. 8.3.1.4 DRV (Gate Drive)
        5. 8.3.1.5 CS (Current Sense)
        6. 8.3.1.6 CBC (Cable Compensation), Pin 1 UCC28700
        7. 8.3.1.7 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. 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. 9.2.2.1 Transformer Parameter Verification
        2. 9.2.2.2 Output Capacitance
        3. 9.2.2.3 VDD Capacitance, CDD
        4. 9.2.2.4 VDD Start-Up Resistance, RSTR
        5. 9.2.2.5 VS Resistor Divider, Line Compensation, and Cable Compensation
        6. 9.2.2.6 Input Bulk Capacitance and Minimum Bulk Voltage
        7. 9.2.2.7 Transformer Turns Ratio, Inductance, Primary-Peak Current
        8. 9.2.2.8 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. 12.1.1.1  Capacitance Terms in Farads
        2. 12.1.1.2  Duty Cycle Terms
        3. 12.1.1.3  Frequency Terms in Hertz
        4. 12.1.1.4  Current Terms in Amperes
        5. 12.1.1.5  Current and Voltage Scaling Terms
        6. 12.1.1.6  Transformer Terms
        7. 12.1.1.7  Power Terms in Watts
        8. 12.1.1.8  Resistance Terms in Ω
        9. 12.1.1.9  Timing Terms in Seconds
        10. 12.1.1.10 Voltage Terms in Volts
        11. 12.1.1.11 AC Voltage Terms in VRMS
        12. 12.1.1.12 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
  14. IMPORTANT NOTICE

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DATA SHEET

UCC2870x Constant-Voltage, Constant-Current Controller With Primary-Side Regulation

1 Features

  • < 30-mW No-Load Power for 5-Star Rating
  • Primary-Side Regulation (PSR) Eliminates Opto-Coupler
  • ±5% Voltage and Current Regulation
  • 130-kHz Maximum Switching Frequency Enables High-Power Density Charger Designs
  • Quasi-Resonant Valley-Switching Operation for Highest Overall Efficiency
  • Patent-Pending Frequency-Jitter Scheme to Ease EMI Compliance
  • Wide VDD Range Allows Small Bias Capacitor
  • Clamped Gate-Drive Output for MOSFET
  • Protection Functions: Overvoltage, Low-Line, and Overcurrent
  • Programmable Cable Compensation (UCC28700 Only)
  • NTC Resistor Interface (UCC28701, UCC28702 and UCC28703 Only) With Fixed Cable Compensation Options
  • SOT-23 Package

2 Applications

  • USB-Compliant Adapters and Chargers for Consumer Electronics (Cell Phones, Tablets and Cameras)
  • AC and DC Power Supplies

3 Description

The UCC28700 family of flyback power supply controllers provides Constant-Voltage (CV) and Constant-Current (CC) output regulation without the use of an optical coupler. The devices process information from the primary power switch and an auxiliary flyback winding for precise control of output voltage and current. Low start-up current, dynamically controlled operating states and a tailored modulation profile support very low standby power without sacrificing start-up time or output transient response.

Control algorithms in the UCC28700 family allow operating efficiencies to meet or exceed applicable standards. The output drive interfaces to a MOSFET power switch. Discontinuous Conduction Mode (DCM) with valley switching reduces switching losses. Modulation of switching frequency and primary current peak amplitude (FM and AM) keeps the conversion efficiency high across the entire load and line ranges.

The controllers have a maximum switching frequency of 130 kHz and always maintain control of the peak-primary current in the transformer. Protection features help keep primary and secondary component stresses in check. The UCC28700 allows the level of cable compensation to be programmed. The UCC28701, UCC28702, and UCC28703 devices allow remote temperature sensing using a Negative Temperature Coefficient (NTC) resistor while providing fixed cable-compensation levels.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)
UCC28700 SOT-23 (6) 2.90 mm × 1.60 mm
UCC28701
UCC28702
UCC28703
  1. For all available packages, see the orderable addendum at the end of the datasheet.

Typical Application Schematic

app1_slusb41.gif

4 Revision History

Changes from * Revision (July 2012) to A Revision

  • Added Handling Rating table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section Go

5 Device Comparison Table(1)(2)

PART NUMBER VERSION
UCC28700 Programmable cable compensation
UCC28701 NTC, 0 mV (at 5-V output) cable compensation option
UCC28702 NTC, 150 mV (at 5-V output) cable compensation option
UCC28703 NTC, 300 mV (at 5-V output) cable compensation option
(1) See Addendum for specific device ordering information.
(2) For other fixed cable compensation options, please consult the factory.

6 Pin Configuration and Functions

pin_slusb41.gif

Pin Functions

PIN I/O DESCRIPTION
NAME UCC28700 UCC28701/2/3
NO. NO.
CBC 1 — I Cable Compensation (CBC) is a programming pin for compensation of cable voltage drop. Cable compensation is programmed with a resistor to GND.
CS 4 4 I Current Sense (CS) input connects to a ground-referenced current-sense resistor in series with the power switch. The resulting voltage is used to monitor and control the peak primary current. A series resistor can be added to this pin to compensate the peak switch current levels as the AC-mains input varies.
DRV 3 3 O Drive (DRV) is an output used to drive the gate of an external high voltage MOSFET switching transistor.
GND 5 5 — The Ground (GND) pin is both the reference pin for the controller and the low-side return for the drive output. Special care should be taken to return all AC decoupling capacitors as close as possible to this pin and avoid any common trace length with analog signal return paths.
NTC — 1 I NTC is an interface to an external NTC (negative temperature coefficient) resistor for remote temperature sensing. Pulling this pin low shuts down PWM action.
VDD 2 2 — VDD is the bias supply input pin to the controller. A carefully-placed bypass capacitor to GND is required on this pin.
VS 6 6 I Voltage Sense (VS) is an input used to provide voltage and timing feedback to the controller. This pin is connected to a voltage divider between an auxiliary winding and GND. The value of the upper resistor of this divider is used to program the AC-mains run and stop thresholds and line compensation at the CS pin.

 
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