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

1 Introduction

The Programmable Logic Controllers (PLC) are widely used for automation in industries. The PLC collects data from sensors, analyze this data, and controls the industrial process through actuators. One way of collecting data from different sensors is through current loops. The sensor transmitters convert the measured parameter in to a current output and the current is transmitted over a cable to analog input module for measurement. The analog input module converts the analog current value in to a digital value by measuring the voltage drop across burden resistor. Figure 1-1 illustrates an analog input module with current inputs.

GUID-20201210-CA0I-LZND-SQTX-Q6KK2D8KGSMX-low.gif Figure 1-1 Current input protection in Analog Input modules

The Digital values of sensor outputs are transmitted to PLC CPU through the backplane. Due to miswiring and transients on current input, the analog input module needs protection components on current inputs. Section 2 describes the protection required for current inputs in analog input modules