SBOA597 November   2024 OPA928

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Architecture of Small Current Measurement
    1. 2.1 Coulombmeter
    2. 2.2 Using the Coulombmeter to Determine IB
    3. 2.3 Leakage of Integration Capacitor
  6. 3Benchmarking
    1. 3.1 Point to Point Wiring
    2. 3.2 Shielding
    3. 3.3 PCB Cleaning
    4. 3.4 Temperature Stability
  7. 4Calibration Using a Coulombmeter for Application Circuits
    1. 4.1 Calibration of Common Application Circuits
    2. 4.2 Calibration of Inverting Input
    3. 4.3 Calibration of Non-Inverting Input
    4. 4.4 Determine Resistance of the Capacitor Using Zero-Cross Method
    5. 4.5 Dielectric Absorption and Relaxation
    6. 4.6 Calibration at 85°C
    7. 4.7 Calibration at 25C
  8. 5Summary
  9. 6References

Summary

As a result, we obtained calibration data for the coulombmeter at 85°C and 25°C. At the same time, we obtained resistance of the capacitor at 85°C and at 25°C as 19.8PΩ and 106PΩ, respectively. The number can be used for the application circuit as the same capacitor can be used for the application.

We also obtained dielectric absorption time for 85C and at 25°C as 300 minute and 90 minute, respectively.

Table 5-1 Result of the Calibration at two Different Temperatures
Unit 85°C 25°C
Bias current of the coulombmeter Atto-Ampere -354.8 to -357.6 78.4 to 79
Resistance of the integration capacitor Peta Ω 19.8 106
Dielectric absorption time min 300 90

This document demonstrates the calibration of low current measurement in tens of atto-Ampere in resolution.