SLVS543P August   2004  – November 2018 TL431 , TL432

PRODUCTION DATA.  

  1. Features
  2. Applications
    1.     Simplified Schematic
  3. Description
  4. Revision History
  5. Device Comparison Table
  6. Pin Configuration and Functions
    1.     Pin Functions
  7. Specifications
    1. 7.1  Absolute Maximum Ratings
    2. 7.2  ESD Ratings
    3. 7.3  Thermal Information
    4. 7.4  Recommended Operating Conditions
    5. 7.5  Electrical Characteristics, TL431C, TL432C
    6. 7.6  Electrical Characteristics, TL431I, TL432I
    7. 7.7  Electrical Characteristics, TL431Q, TL432Q
    8. 7.8  Electrical Characteristics, TL431AC, TL432AC
    9. 7.9  Electrical Characteristics, TL431AI, TL432AI
    10. 7.10 Electrical Characteristics, TL431AQ, TL432AQ
    11. 7.11 Electrical Characteristics, TL431BC, TL432BC
    12. 7.12 Electrical Characteristics, TL431BI, TL432BI
    13. 7.13 Electrical Characteristics, TL431BQ, TL432BQ
    14. 7.14 Typical Characteristics
  8. Parameter Measurement Information
  9. Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
    4. 9.4 Device Functional Modes
      1. 9.4.1 Open Loop (Comparator)
      2. 9.4.2 Closed Loop
  10. 10Applications and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Applications
      1. 10.2.1 Comparator With Integrated Reference
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
          1. 10.2.1.2.1 Basic Operation
            1. 10.2.1.2.1.1 Overdrive
          2. 10.2.1.2.2 Output Voltage and Logic Input Level
            1. 10.2.1.2.2.1 Input Resistance
        3. 10.2.1.3 Application Curve
      2. 10.2.2 Shunt Regulator/Reference
        1. 10.2.2.1 Design Requirements
        2. 10.2.2.2 Detailed Design Procedure
          1. 10.2.2.2.1 Programming Output/Cathode Voltage
          2. 10.2.2.2.2 Total Accuracy
          3. 10.2.2.2.3 Stability
          4. 10.2.2.2.4 Start-Up Time
        3. 10.2.2.3 Application Curve
    3. 10.3 System Examples
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Nomenclature
    2. 13.2 Related Links
    3. 13.3 Receiving Notification of Documentation Updates
    4. 13.4 Community Resources
    5. 13.5 Trademarks
    6. 13.6 Electrostatic Discharge Caution
    7. 13.7 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

Output Voltage and Logic Input Level

In order for TL431 to properly be used as a comparator, the logic output must be readable by the receiving logic device. This is accomplished by knowing the input high and low level threshold voltage levels, typically denoted by VIH & VIL.

As seen in Figure 26, TL431's output low level voltage in open-loop/comparator mode is ~2 V, which is typically sufficient for 5V supplied logic. However, would not work for 3.3 V & 1.8 V supplied logic. In order to accomodate this a resistive divider can be tied to the output to attenuate the output voltage to a voltage legible to the receiving low voltage logic device.

TL431's output high voltage is equal to VSUP due to TL431 being open-collector. If VSUP is much higher than the receiving logic's maximum input voltage tolerance, the output must be attenuated to accomadate the outgoing logic's reliability.

When using a resistive divider on the output, be sure to make the sum of the resistive divider (R1 & R2 in Figure 25) is much greater than RSUP in order to not interfere with TL431's ability to pull close to VSUP when turning off.