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

4.2 Specs of Comparator Mode

  • VOL: As table 2 suggests, TL and ATL devices have VOL close to 2 V and TLV and TLVH devices have VOL close to 1 V. Please refer to application note SLVA987 for more detail of VOL variation over IKA, IREF and temperature.
  • Propagation delay: Designers prefer fast response in the comparator mode in their designs. Faster response of the comparator mode in power vsupply design saves power by switching the PWM controller faster in the design example given in the figure. Table 4-2 lists the typical TPHL for 431 devices when the supply is ramped up from 4.5 V to 6 V to the output of the comparator settles within 5% of the VOL value for the no load capacitor.
Table 4-2 Typical Propagation Delay (Settled Response) of Devices
Device TPHL (μs)
TL431 1.5
TL431LI 1.2
ATL431 10
ATL431LI 1.2

Below are the scope shots for TPLH for different devices.

Figure 4-2 Propagation Delay (TPLH): TL431
Figure 4-3 Propagation Delay (TPLH): TL431LI
Figure 4-4 Propagation Delay (TPLH): ATL431
Figure 4-5 Propagation Delay (TPLH): ATL431LI

Shunt regulators from TI (TL431 , TL431, ATL431 & ATL431LI) have < 10 us typical response time and can be used for faster systems.