TIDUFG2 December   2025

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Terminology
    2. 1.2 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Sensor Selection
    3. 2.3 Highlighted Products
      1. 2.3.1 TLV387
      2. 2.3.2 TLV9054
      3. 2.3.3 MSPM0G5187-LP
      4. 2.3.4 LOG300
      5. 2.3.5 UCC28881
      6. 2.3.6 TPS709
  9. 3System Design Theory
    1. 3.1 Current Sensor
    2. 3.2 Hybrid Integrator
    3. 3.3 Band-Pass Filter
      1. 3.3.1 Log Amplifier
      2. 3.3.2 Current Low-Pass Filter
      3. 3.3.3 Non-isolated Voltage Sensing
      4. 3.3.4 Auto Labeling Circuit
        1. 3.3.4.1 Line Voltage Sensing
        2. 3.3.4.2 Arc Gap Voltage Sensing
        3. 3.3.4.3 Differential to Single-Ended Conversion
      5. 3.3.5 Power Supply
  10. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Hardware Requirements
    2. 4.2 Software
    3. 4.3 Test Setup
      1. 4.3.1 Arc Testing Setup
    4. 4.4 Test Results
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
    2. 5.2 Tools and Software
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks
  12. 6About the Author

3.3.1 Log Amplifier

TIDA-010971 LOG300 Schematic Figure 3-9 LOG300 Schematic

The LOG300 analog front end includes a low-noise amplifier (LNA) and log detector built into the same integrated circuit. The integrator output feeds into the LOG300 to buffer the PCB Rogowski. Jumper R70 connects the PCB Rogowski directly to the LNA. R68 and R69 optionally disable the AFE for power evaluation purposes. The band-pass filter functions as a fourth order 1MHz to 10MHz filter. A 10MHz first order band-pass filter creates with a single LC pair, 330pF for C18 and 681nH for L4. The unused passive components in series must have jumpers and the parallel LC pair must be depopulated. Compared to the fourth order filter more noise from loads appears in the first order filter log detector circuit output.

R15 and C10 adjust the magnitude and settling time of the LOG300 output. A lower value for R15 reduces the sensitivity. Higher C10 smooths the output. More details about the setup and evaluation of the LOG300 appear in the data sheet. The R15 and C10 values chosen form a low-pass filter with a settling time around 0.183ms. This provides enough detail to detect arcing edges compared to typical noise from loads.