SLVS905B December   2008  – July 2024 TLV431A-Q1 , TLV431B-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
    1.     Pin Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Thermal Information
    4. 5.4 Recommended Operating Conditions
    5. 5.5 Electrical Characteristics for TLV431A-Q1
    6. 5.6 Electrical Characteristics for TLV431B-Q1
    7. 5.7 Typical Characteristics
  7. 6 Parameter Measurement Information
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
    4. 7.4 Device Functional Modes
      1. 7.4.1 Open Loop (Comparator)
      2. 7.4.2 Closed Loop
  9. 8 Applications and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Comparator with Integrated Reference (Open Loop)
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Basic Operation
          2. 8.2.1.2.2 Overdrive
          3. 8.2.1.2.3 Output Voltage and Logic Input Level
            1. 8.2.1.2.3.1 Input Resistance
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Shunt Regulator/Reference
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 Programming Output/Cathode Voltage
          2. 8.2.2.2.2 Total Accuracy
          3. 8.2.2.2.3 Stability
        3. 8.2.2.3 Application Curve
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  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

Package Options

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

8.1 Application Information

Figure 8-1 shows the TLV431A, or TLV431B used in a 3.3V isolated flyback supply. Output voltage VO can be as low as reference voltage VREF (1.24V ± 1%). The output of the regulator, plus the forward voltage drop of the optocoupler LED (1.24 + 1.4 = 2.64 V), determine the minimum voltage that can be regulated in an isolated supply configuration. Regulated voltage as low as 2.7Vdc is possible in the topology shown in Figure 8-1.

The 431 family of devices are prevalent in these applications, being designers go to choice for secondary side regulation. Due to this prevalence, this section explains the operation and design in both states of TLV431 that this application sees, open loop (Comparator + Vref) & closed loop (Shunt Regulator).

Further information about system stability and using a TLV431 device for compensation can be found in the application note Compensation Design With TL431 for UCC28600, SLUA671.

TLV431A-Q1 TLV431B-Q1 Flyback With Isolation Using TLV431, TLV431A, or TLV431B as Voltage Reference and Error AmplifierFigure 8-1 Flyback With Isolation Using TLV431, TLV431A, or TLV431B as Voltage Reference and Error Amplifier