SNOSDG9 December   2024 TLV1922

PRODMIX  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
    1.     Pin Configuration: TLV1921
    2.     Pin Configurations: TLV1922
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Thermal Information - Single
    4. 5.4 Thermal Information - Dual
    5. 5.5 Recommended Operating Conditions
    6. 5.6 Electrical Characteristics
    7. 5.7 Switching Characteristics
    8. 5.8 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagrams
    3. 6.3 Feature Description
    4. 6.4 Device Functional Modes
      1. 6.4.1 Inputs
        1. 6.4.1.1 Input Voltage and Common Mode Voltage Ranges
        2. 6.4.1.2 Fail-Safe Inputs
        3. 6.4.1.3 Unused Inputs
      2. 6.4.2 Open-Drain Output
      3. 6.4.3 Reference Output
      4. 6.4.4 Power-On Reset (POR)
      5. 6.4.5 Internal Hysteresis
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Basic Comparator Definitions
        1. 7.1.1.1 Operation
        2. 7.1.1.2 Propagation Delay
        3. 7.1.1.3 Overdrive Voltage
      2. 7.1.2 Hysteresis
        1. 7.1.2.1 Inverting and Non-Inverting Hysteresis using Open-Drain Output
    2. 7.2 Typical Applications
      1. 7.2.1 Window Comparator
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
        3. 7.2.1.3 Application Curve
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Related Documentation
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.2.1.2 Detailed Design Procedure

Configure the circuit as shown in the circuit above where the 2.5V REF from the TLV192x is used as the reference voltage and the resistor string of R1, R2, and R3 define the upper and lower threshold voltages for the 24V PLC power supply. When the comparator detects that the 24V supply has exceeded the maximum voltage of 30V or has drooped below the minimum voltage of 19.2V, ALERT_BAR is pulled to a logic LOW state.

The first step is to determine the sum total resistance of the resistor string (R1, R2, R3) using the dissipation limit of 30uA. With a maximum operating voltage of 30V, the resistor string draws 30uA if the total resistance of R1+R2+R3 is 1Mohm.

The second step is to set the value of R3 such that the lower comparator changes output state from HIGH to LOW when the 24V supply reaches 30V. This is achieved when the voltage at the junction of R2 and R3 is equal to the reference voltage of 2.5V. Since 30uA is passing through the resistor string at 30V, R3 can be calculated from 2.5V / 30uA which is approximately 83.3kohms.

The third step is to set the value of R2 such that the upper comparator changes output state from HIGH to LOW when the 24V supply reaches 19.2V. This is achieved when the voltage at the junction of R1 and R2 is equal to the reference voltage of 2.5V. Since 19.2uA passes through the resistor string at 19.2V, R2 can be calculated from (2.5V /19.2uA) - R3 which is approximately 46.9kohms.

Lastly, the value of R1 is calculated from 1Mohm - (R2 + R3) which is approximately 870kohms. Please note that standard 1% resistor values were selected for the circuit.

The respective comparator outputs (ALERT_BAR) are LOW when the 24V PLC power supply is less than 19.2V or greater than 30V. Likewise, the respective comparator outputs are HIGH when the 24V supply is within the range of 19.2V to 30V (within the "window"), as shown below.