SLUS873C January   2009  – December 2016 UC1825A-SP

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  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 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 Leading Edge Blanking
      2. 8.3.2 UVLO, Soft-Start, and Fault Management
      3. 8.3.3 Active Low Outputs During UVLO
      4. 8.3.4 Control Methods
      5. 8.3.5 Synchronization
      6. 8.3.6 High Current Outputs
      7. 8.3.7 Open Loop Test Circuit
    4. 8.4 Device Functional Modes
  9. 9 Application 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  Auxiliary Supply Voltage
        2. 9.2.2.2  Oscillator Frequency
        3. 9.2.2.3  Preliminary Considerations
        4. 9.2.2.4  Input Power
        5. 9.2.2.5  Primary Current
        6. 9.2.2.6  Sense Resistor R(s)
        7. 9.2.2.7  MOSFET DC Losses
        8. 9.2.2.8  Selection of Core Material
        9. 9.2.2.9  Main Transformer Design
        10. 9.2.2.10 Calculation of Transformer
        11. 9.2.2.11 Minimum Core Size
        12. 9.2.2.12 Core Loss Limited Conditions
        13. 9.2.2.13 Core Geometry Selection
        14. 9.2.2.14 Wire Size Selection
        15. 9.2.2.15 Calculate Secondary RMS Current
        16. 9.2.2.16 Transformer Assembly
        17. 9.2.2.17 Calculation of Winding Resistances and Losses
        18. 9.2.2.18 Transformer Power Losses
        19. 9.2.2.19 Output Section
          1. 9.2.2.19.1 Output Choke Calculations
          2. 9.2.2.19.2 Output Capacitor
          3. 9.2.2.19.3 Output Diodes
        20. 9.2.2.20 UC1825A-SP PWM Control Section
          1. 9.2.2.20.1 Current Limit and Shutdown
          2. 9.2.2.20.2 Ramp
          3. 9.2.2.20.3 Slope Compensation
        21. 9.2.2.21 Closing the Feedback Loop
          1. 9.2.2.21.1 Error Amplifier
          2. 9.2.2.21.2 Control to Output Gain
          3. 9.2.2.21.3 Error Amplifier Compensation
          4. 9.2.2.21.4 Dynamic Performance
          5. 9.2.2.21.5 Short Circuit
          6. 9.2.2.21.6 Circuit Power Losses
        22. 9.2.2.22 Summary
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Feedback Traces
      2. 11.1.2 Input/Output Capacitors
      3. 11.1.3 Compensation Components
      4. 11.1.4 Traces and Ground Planes
      5. 11.1.5 Ground Planes
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Community Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

1 Features

  • QML-V Qualified, SMD 5962-87681
  • 5962P8768105Vxx:
    • Radiation Hardness Assurance (RHA) up to
      30-krad(Si) Total Ionizing Dose (TID)
    • Passes Functional and Specified Post-Radiation Parametric Limits at 45 krad at LDR (10 mrad(Si)/s) per 1.5× Over Test as Defined in MIL-STD-883 Test Method 1019.9 Paragraph 3.13.3.b
    • Exhibits Low Dose Rate Sensitivity but Remains Within the Pre-Radiation Electrical Limits at 30-krad Total Dose Level, as Allowed by MIL-STD-883, TM1019
  • Compatible With Voltage-Mode or Current-Mode Control Methods
  • Practical Operation at Switching Frequencies
    to 1 MHz
  • 50-ns Propagation Delay to Output
  • High-Current Dual Totem Pole Outputs
    (2-A Peak)
  • Trimmed Oscillator Discharge Current
  • Low 100-μA Start-Up Current
  • Pulse-by-Pulse Current Limiting Comparator
  • Latched Overcurrent Comparator With Full Cycle Restart
  • Qualified Over the Military Temperature Range (–55°C to 125°C)

2 Applications

  • Radiation-Hardened DC-DC Converters
  • Satellite Buses and Payloads
  • Space Launch Vehicles
  • Undersea Cabling
  • Supports Various Topologies:
    • Flyback, Forward, Buck, Boost
    • Push-Pull, Half-Bridge, Full Bridge With External Interface Circuit

3 Description

The UC1825A-SP PWM controller is a radiation hardened version of the standard UC1825 family. Performance enhancements have been made to several of the circuit blocks. Error amplifier gain bandwidth product is 12 MHz, while input offset voltage is 2 mV. Current limit threshold is assured to a tolerance of 5%. Oscillator discharge current is specified at 10 mA for accurate dead time control. Frequency accuracy is improved to 6%. Start-up supply current, typically
100 μA, is ideal for offline applications. The output drivers are redesigned to actively sink current during UVLO at no expense to the start-up current specification. In addition each output is capable of
2-A peak currents during transitions.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)
UC1825A-SP CDIP (16) 19.56 mm × 6.92 mm
UC1825A-SP RHA CDIP (16) 19.56 mm × 6.92 mm
CFP (16) 10.16 mm × 7.10 mm
  1. For all available packages, see the orderable addendum at the end of the data sheet.

Block Diagram

UC1825A-SP UDG-02091_SLUS334.gif