SNVAA58 December   2022 ATL431 , ATL431LI , TL431 , TL431LI

 

  1.    Abstract
  2. 1Trademarks
  3. 2Comparator Mode
    1. 2.1 Input Threshold Voltage (VIT)
    2. 2.2 Output Levels (VOH , VOL)
    3. 2.3 Propagation Delay
  4. 3Design Parameters for Comparator Mode
    1. 3.1 IREF (Reference Current)
    2. 3.2 IKA (Cathode Current)
    3. 3.3 Stability
      1. 3.3.1 Load Capacitor (Cathode to Anode)
      2. 3.3.2 Compensation in Comparator Mode in Feedback of PWM Controller
  5. 4Design Example
    1. 4.1 Input Parameters
    2. 4.2 Specs of Comparator Mode
  6. 5Conclusion
  7. 6Revision History

2 Comparator Mode

The 431 family of TI shunt regulators are used in the comparator mode by opening the DC feedback path, when there is no DC current from cathode to reference pin. Below are examples of circuits for shunt regulators in the comparator mode. Figure 2-1 shows the simple comparator circuit and Figure 2-2 shows the typical type II compensation which is used in isolated power supply designs with optocoupler feedback. This section discusses the specs of the family 431 in comparator mode.

Figure 2-1 Basic Comparator Mode
Figure 2-2 Comparator with Type 2 Compensation