SNOAA35D April   2023  – December 2023 LM2901 , LM2901B , LM2901B-Q1 , LM2903 , LM2903-Q1 , LM2903B , LM2903B-Q1 , LM339 , LM339-N , LM393 , LM393-N , LM393B , LM397 , TL331 , TL331-Q1 , TL331B

 

  1.   1
  2.   Application Design Guidelines for LM339, LM393, TL331 Family Comparators Including the New B-versions
  3.   Trademarks
  4. 1 Devices Covered in Application Note
    1. 1.1 Base Part Numbers
    2. 1.2 Input Voltage Offset Grades
    3. 1.3 Maximum Supply Voltage
    4. 1.4 High Reliability Options
  5. 2 The New TL331B, TL391B, LM339B, LM393B, LM2901B and LM2903B B Versions
    1. 2.1 PCN to Change Classic Die to a New Die Design
      1. 2.1.1 Determine Die Used for Single TL331 and Dual LM293, LM393, and LM2903
      2. 2.1.2 Determine Die Used for Quad LM139, LM239, LM339, and LM2901
      3. 2.1.3 Device PCN Summary
    2. 2.2 Changes to Package Top Markings
  6. 3 Input Considerations
    1. 3.1  Input Stage Schematic – The Classic LM339 Family
    2. 3.2  Input Stage Schematic - New B Devices
    3. 3.3  Differences Between the Classic and B Die Devices
    4. 3.4  Input Voltage Range
    5. 3.5  Input Voltage Range vs. Common Mode Voltage Range
    6. 3.6  Reason for Input Range Headroom Limitation
    7. 3.7  Input Voltage Range Feature
      1. 3.7.1 Both Inputs Above Input Range Behavior
    8. 3.8  Negative Input Voltages
      1. 3.8.1 Maximum Input Current
      2. 3.8.2 Phase Reversal or Inversion
      3. 3.8.3 Protecting Inputs from Negative Voltages
        1. 3.8.3.1 Simple Resistor and Diode Clamp
        2. 3.8.3.2 Voltage Divider with Clamp
          1. 3.8.3.2.1 Split Voltage Divider with Clamp
    9. 3.9  Power-Up Behavior
    10. 3.10 Capacitors and Hysteresis
    11. 3.11 Output to Input Cross-Talk
  7. 4 Output Stage Considerations
    1. 4.1 Output VOL and IOL
    2. 4.2 Pull-Up Resistor Selection
    3. 4.3 Short Circuit Sinking Current
    4. 4.4 Pulling Output Up Above VCC
    5. 4.5 Negative Voltages Applied to Output
    6. 4.6 Adding Large Filter Capacitors To Output
  8. 5 Power Supply Considerations
    1. 5.1 Supply Bypassing
      1. 5.1.1 Low VCC Guidance
      2. 5.1.2 Split Supply use
  9. 6 General Comparator Usage
    1. 6.1 Unused Comparator Connections
      1. 6.1.1 Do Not Connect Inputs Directly to Ground
      2. 6.1.2 Unused Comparator Input Connections
      3. 6.1.3 Leave Outputs Floating
      4. 6.1.4 Prototyping
  10. 7 PSPICE and TINA TI Models
  11. 8 Conclusion
  12. 9 Related Documentation
    1. 9.1 Related Links
  13. 10Revision History

3.5 Input Voltage Range vs. Common Mode Voltage Range

The phrases Common Mode Voltage Range and Input Voltage Range tend to be used interchangeably, but there is an important difference when discussing comparators. The common definition of Common Mode Voltage (CMVR or CMR) is the average of the inverting (-IN) and non-inverting (+IN) input voltages. This definition is acceptable for operational amplifiers where the inputs are kept to less than a millivolt of each other due to negative feedback, but comparator inputs are rarely kept at the same potential and can see several volts of differential voltage under normal operation. If the average value is used, there can be an instance where one input voltage slightly exceeds the input range specification, and the average of the two inputs can still reside within the input range, even though that one input is violating the input range. The average gives a false impression of meeting the input voltage range requirement.

Note:

The input voltage limits must be considered per input and NOT the average of the two input voltages. If, for example, the calculated input voltage limit is 3.5 V, then neither input can exceed 3.5 V.