SNOAA91 may   2023 TLV1812 , TLV1851 , TLV7011

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Input Types
    1. 2.1 Classic Bipolar Inputs
    2. 2.2 ESD Protected Inputs
    3. 2.3 "Fail-Safe" and "Fault Tolerant" Inputs
      1. 2.3.1 LM339 Family - The Original "Fail-Safe" Input
      2. 2.3.2 Modern "Fail-Safe" Inputs
    4. 2.4 "Over-the-Rail" Inputs
  6. 3Identifying The Difference Between The Input Types
    1. 3.1 Older Bipolar Device Inputs
    2. 3.2 Identifying ESD Clamped Inputs
    3. 3.3 Identifying "Failsafe" or "Over-The-Rail" Inputs
  7. 4Precautions for "Failsafe" and "Over-The-Rail" Inputs
  8. 5Negative Input Voltages
  9. 6Input Types Comparison Table
  10. 7Summary
  11. 8References

3.3 Identifying "Failsafe" or "Over-The-Rail" Inputs

If the upper input voltage is an absolute number, such as "36 V" or "6 V", then that is a sign that there are not any upper ESD clamps.

GUID-20230215-SS0I-3ZLD-XBHL-57GJX6J84TQD-low.svg Figure 3-3 Example of LM339 Abs Max Table for Failsafe Inputs

The above table from the LM339 data sheet Absolute Maximum Ratings table shows an example failsafe inputs with no upper ESD clamps. Notice that the "Input Voltage Range" line is not referenced to the supply and contains an absolute number of 36 V.

"Over-The -Rail" inputs are not as common as "Fail-Safe" inputs (more difficult to implement) and are prominently mentioned on the data sheet front page Features section, specification table table footnotes, or Applications Section.