SGLS164A April   2003  – October 2024 UC2842AQ , UC2843AQ , UC2845AQ

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 Electrical Characteristics
    4. 5.4 Typical Characteristics
  7. 6 Parameter Measurement Information
  8. 7 Detailed Description
    1. 7.1 Functional Block Diagram
  9. 8 Application and Implementation
    1. 8.1 Application Information
  10. 9 Device and Documentation Support
    1. 9.1 Receiving Notification of Documentation Updates
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

8.1 Application Information

UC2842AQ UC2843AQ UC2844AQ UC2845AQ Oscillator Figure 8-1 Oscillator
UC2842AQ UC2843AQ UC2844AQ UC2845AQ Open-Loop Laboratory Text Fixture Figure 8-2 Open-Loop Laboratory Text Fixture

High peak currents associated with capacitive loads necessitate careful grounding techniques. Timing and bypass capacitors must be connected close to pin 5 in a single point ground. The transistor and 5k potentiometer are used to sample the oscillator waveform and apply an adjustable ramp to pin 3.

UC2842AQ UC2843AQ UC2844AQ UC2845AQ Slope Compression Figure 8-3 Slope Compression

A fraction of the oscillator ramp can be resistively summed with the current sense signal to provide slope compensation for converters requiring duty cycles over 50%. Note that capacitor, C, forms a filter with R2 to suppress the leading edge switch spikes.

UC2842AQ UC2843AQ UC2844AQ UC2845AQ Off-Line Flyback Regulator Figure 8-4 Off-Line Flyback Regulator

  1. Input Voltage: 95 VAC to 130 VAC (50Hz/60Hz)
  2. Line Isolation: 3750V
  3. Switching Frequency 40 kHz
  4. Efficiency, Full Load: 70%
  5. Output Voltage:
    1. +5V, ±5%; 1A to 4A Load
    2. +12V, ±3%; 0.1A to 0.3A Load Ripple voltage: 100 mV P-P Max
    3. –12V, ±3%; 0.1A to 0.3A Load Ripple voltage: 100 mV P-P Max