SLUS224F September   1994  – October 2017 UC1842A , UC1843A , UC1844A , UC1845A , UC2842A , UC2843A , UC2844A , UC2845A , UC3842A , UC3843A , UC3844A , UC3845A

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Pulse-by-Pulse Current Limiting
      2. 7.3.2 Current Sense Circuit
      3. 7.3.3 Error Amplifier Configuration
      4. 7.3.4 Undervoltage Lockout
      5. 7.3.5 Oscillator
    4. 7.4 Device Functional Modes
      1. 7.4.1 Normal Operation
      2. 7.4.2 Undervoltage Lockout (UVLO) Start-Up
      3. 7.4.3 UVLO Turnoff Mode
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Custom Design With WEBENCH® Tools
        2. 8.2.2.2 UC2842A Design Procedure
      3. 8.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 Custom Design With WEBENCH® Tools
      2. 11.1.2 Device Nomenclature
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Related Links
    4. 11.4 Receiving Notification of Documentation Updates
    5. 11.5 Community Resources
    6. 11.6 Trademarks
    7. 11.7 Electrostatic Discharge Caution
    8. 11.8 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

Features

  • Optimized for Off-Line and DC-DC Converters
  • Low Start-Up Current (< 0.5 mA)
  • Trimmed Oscillator Discharge Current
  • Automatic Feedforward Compensation
  • Pulse-by-Pulse Current Limiting
  • Enhanced Load Response Characteristics
  • Undervoltage Lockout With Hysteresis
  • Double Pulse Suppression
  • High-Current Totem Pole Output
  • Internally-Trimmed Bandgap Reference
  • Up to 500-kHz Operation
  • Create a Custom Design Using the UCx84xA With the WEBENCH® Power Designer

Applications

  • Switch Mode Power Supplies (SMPS)
  • DC-DC Converters
  • Power Modules
  • Industrial PSU
  • Battery Operated PSU

Description

The UCx84xA family of control devices is a pin-for-pin compatible improved version of the UCx84x family. Providing the necessary features to control current-mode or switched-mode power supplies, this family of devices has many improved features: startup current is less than 0.5 mA, oscillator discharge is trimmed to 8.3 mA, and during UVLO, the output stage can sink at least 10 mA at less than 1.2 V for VCC over 5 V.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)
UC1842A, UC1843A, UC1844A, UC1845A CDIP (8) 6.67 mm × 9.60 mm
LCCC (20) 8.89 mm × 8.89 mm
UC2843A PLCC (20) 8.96 mm × 8.96 mm
UC2842A, UC2843A, UC2844A, UC2845A,
UC3842A, UC3843A, UC3844A, UC3845A
PDIP (8) 6.35 mm × 9.81 mm
SOIC (8) 3.91 mm × 4.90 mm
SOIC (14) 3.91 mm × 8.65 mm
SOIC (16) 7.50 mm × 10.30 mm
  1. For all available packages, see the orderable addendum at the end of the data sheet.

Device Comparison Table

DEVICE UVLO ON UVLO OFF MAX DUTY CYCLE
UC1842A 16 V 10 V <100%
UC1843A 8.4 V 7.6 V <100%
UC1844A 16 V 10 V <50%
UC1845A 8.4 V 7.6 V <50%

Simplified Application Diagram

UC1842A UC1843A UC1844A UC1845A UC2842A UC2843A UC2844A UC2845A UC3842A UC3843A UC3844A UC3845A alt_slus224.gif