SLVAEW6 December   2020 TPS2661

 

  1.   Trademarks
  2. 1Introduction
  3. 2Protection Required for Current Inputs in Analog Input Modules
    1. 2.1 Over-Current Protection from Miswiring to Field Power Supplies
    2. 2.2 Over-Voltage Protection from Miswiring to Field Power Supplies
  4. 3Typical Discrete Circuit for Protection of Current Input
    1. 3.1 Protection Provided by Discrete Circuit
      1. 3.1.1 Over-Current Protection with Discrete Circuit
      2. 3.1.2 Over-voltage Protection with Discrete Circuit
    2. 3.2 Heating and Temperature Rise with Discrete Circuit
    3. 3.3 Reverse Leakage Current of Zener Diodes and Current Measurement Accuracy
  5. 4TPS26610 for Analog Current Loop Protection
    1. 4.1 Current Input Protection with TPS26610
    2. 4.2 Accurate Current Limiting with TPS26610
    3. 4.3 Leakage Current of TPS26610 and Current Measurement Accuracy
    4. 4.4 Protection from Mis-wiring to Field Power Supplies
    5. 4.5 Heating and Temperature Rise with TPS26610
    6. 4.6 Reduction in PCB Size with TPS26610 for Current Input Protection
  6. 5Conclusion

3 Typical Discrete Circuit for Protection of Current Input

A discrete circuit consisting of TVS diode, Zener diodes and PTC is typically used for protection input. TVS diode provides protection from surge pulses, Zener diodes provide protection from over-voltage and PTC provides over-current protection.

Figure 3-1 illustrates an example of a discrete circuit for protection of current inputs in analog input modules. A PTC is required for required for over-current protection while Back-to-Back Zener diodes are required for over-voltage protection and limiting the power dissipation in Burden Resistor in case of miswiring to field supplies. Multiple burden resistors or a MELF resistors (MMB) are required in parallel to dissipate the power in case of miswiring events. A TVS diode is required to protect from surge transients.

GUID-20201210-CA0I-P7MQ-TQSK-NV7MPFXX24LR-low.gif Figure 3-1 Discrete Circuit for Current Input Protection