SLUS224H September   1994  – October 2024 UC1842A , UC1843A , UC1844A , UC1845A , UC2842A , UC2843A , UC2844A , UC2845A , UC3842A , UC3843A , UC3844A , UC3845A

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Pulse-by-Pulse Current Limiting
      2. 6.3.2 Current Sense Circuit
      3. 6.3.3 Error Amplifier Configuration
      4. 6.3.4 Undervoltage Lockout
      5. 6.3.5 Oscillator
    4. 6.4 Device Functional Modes
      1. 6.4.1 Normal Operation
      2. 6.4.2 Undervoltage Lockout (UVLO) Start-Up
      3. 6.4.3 UVLO Turnoff Mode
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Custom Design With WEBENCH® Tools
        2. 7.2.2.2 UC2842A Design Procedure
      3. 7.2.3 Application Curves
  9. 8 Power Supply Recommendations
  10. 9 Layout
    1. 9.1 Layout Guidelines
    2. 9.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Development Support
        1. 10.1.1.1 Custom Design With WEBENCH® Tools
      2. 10.1.2 Device Nomenclature
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 Related Links
    4. 10.4 Receiving Notification of Documentation Updates
    5. 10.5 Support Resources
    6. 10.6 Trademarks
    7. 10.7 Electrostatic Discharge Caution
    8. 10.8 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

Package Options

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

3 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 0.5mA, oscillator discharge is trimmed to 8.3mA, and during UVLO, the output stage can sink at least 10mA at less than 1.2V for VCC over 5V.

Package Information
PART NUMBER PACKAGE(1) PACKAGE SIZE(2)
UC1842A, UC1843A, UC1844A, UC1845A JG (CDIP, 8) 6.67mm × 9.60mm
FK (LCCC, 20) 8.89mm × 8.89mm
UC2843A FN (PLCC, 20) 9.90mm × 9.90mm
UC2842A, UC2843A, UC2844A, UC2845A,
UC3842A, UC3843A, UC3844A, UC3845A		 P (PDIP, 8) 9.81mm × 9.43mm
D (SOIC, 8) 4.90mm × 6.00mm
D (SOIC, 14) 8.65mm × 6.00mm
DW (SOIC, 16) 10.30mm × 10.30mm
(1) For more information, see Section 12.
(2) The package size (length × width) is a nominal value and includes pins, where applicable.
Device Comparison Table
DEVICE UVLO ON UVLO OFF MAX DUTY CYCLE
UC1842A 16V 10V <100%
UC1843A 8.4V 7.6V <100%
UC1844A 16V 10V <50%
UC1845A 8.4V 7.6V <50%
UC1842A UC1843A UC1844A UC1845A UC2842A UC2843A UC2844A UC2845A UC3842A UC3843A UC3844A UC3845A Simplified Application Diagram Simplified Application Diagram