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

3.8.2 Phase Reversal or Inversion

Under certain conditions, the polarity of the output can become incorrect. This scenario, called phase reversal or inversion, occurs when the input of the comparator violates the negative common-mode voltage range. As explained previously, exceeding the positive common mode range tends to result in predictable behavior. But a negative input voltage, relative to the GND pin, can come from unexpected sources, such as switching noise or ground bounce from DC to DC converters. Negative input voltages can also arise from AC capacitor coupled inputs that create a bipolar voltage at the input.

An input voltage of less than –0.3 V can cause parasitic device conduction (Figure 3-5, point A) that results in incorrect output behavior. Operation in this region is not defined in the data sheet as it violates the -0.3V absolute maximum specification for input voltage. The input current turns on internal parasitic NPN transistors that steal current from other internal nodes causing output phase reversal.

Do not try to determine phase reversal performance empirically as different units can have different performance across lots and processes. Negative input voltages must be avoided, assuming a single supply configuration, unless the application can accept either the VOL or VOH level during the duration of the negative input.