TIDUEU6B September   2020  – December 2021 OPA810

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Highlighted Products
      1. 2.2.1 OPA2810
      2. 2.2.2 BUF634A
    3. 2.3 Design Considerations
      1. 2.3.1 Existing architecture
        1. 2.3.1.1 Circuit Stability Issue
        2. 2.3.1.2 Solution in Existing Architecture (Compensation Cap)
      2. 2.3.2 Proposed Design
        1. 2.3.2.1 Stability Analysis of the Proposed Design
          1. 2.3.2.1.1 Without Measurement of Voltage at Inverting Node of A2
          2. 2.3.2.1.2 With Measuring Voltage at Inverting Node of A2
        2. 2.3.2.2 RG = RF Settings and Respective Impedance Ranges
        3. 2.3.2.3 Impedance Measurement Procedure
          1. 2.3.2.3.1 Short Cal
          2. 2.3.2.3.2 Impedance Cal
          3. 2.3.2.3.3 100k Setting Calibration
          4. 2.3.2.3.4 Open Cal
          5. 2.3.2.3.5 Calculations
          6. 2.3.2.3.6 Correction in ZX
          7. 2.3.2.3.7 Data Acquisition and Processing
          8. 2.3.2.3.8 Mathematical Explanation
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Required Hardware and Software
      1. 3.1.1 Hardware
    2. 3.2 Testing and Results
      1. 3.2.1 Test Setup
      2. 3.2.2 Test Results
  9. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
    3. 4.3 PCB Layout Recommendations
      1. 4.3.1 Layout Prints
    4. 4.4 Altium Project
    5. 4.5 Gerber Files
    6. 4.6 Assembly Drawings
  10. 5Software Files
  11. 6Related Documentation
    1. 6.1 Trademarks
    2. 6.2 Third-Party Products Disclaimer
  12. 7Revision History

3.2.2 Test Results

The following example shows the unknown capacitive impedance measurement in detail.

Component : C = 100 nF

Measured value of the C = 99.472 nF

Frequency of Test = 1 kHz

RG = RF Setting = 100 Ω

Calibrated value of RF = 99.97686

RF/ZX = 0.062412398 and α = 90.125° ( phase of the ratio)

Thus, ZX = 1601.875005 and θX = 90.125°

Equation 18. GUID-84C49AEA-BB62-4E10-BEEA-76243DAB1C2F-low.gif
Equation 19. GUID-27886746-6374-424C-86E7-742DF344089D-low.gif
Equation 20. GUID-69DF0623-1322-4FAC-A79E-B1E8D8502598-low.gif
Equation 21. GUID-4A591B57-783C-4B99-A004-678831513AD3-low.gif

Using Equation 21 we get, C = 99.3556 nF

Equation 22. GUID-D6DDD8C4-3566-48BE-BDA6-72F119813C2B-low.gif

Thus the % Error = 0.116 %

All other components are measured in the same way. The results are shown in Table 3-4.

It should be noted that the errors are estimated with respect to the value estimated by Keysight Technologies’ E4980A precision LCR Meter. For testing, an input of 3.6 Vpp was used and results were measured with a seperate board utilizing the THS4551 and ADS9224R.

Table 3-4 Board Measurement Results
ParametersRG = RF Setting
Frequency (Hz)Component100 ΩError(%)5 kΩError(%)100 kΩError(%)
100R1 Ω – 900 Ω0.74500 Ω – 50 kΩ0.1110 kΩ – 10 MΩ0.3
L1.59 mH – 2.38 H1.182.27 H – 79.5 H-72.9 H – 1432 H-
C1.05 µF – 1.59 mF331.78 nF - 1.11 µF0.621.76 nF - 34.7 nF0.36
1kR1 Ω – 900 Ω0.72500 Ω – 50 kΩ0.1210 kΩ – 10 MΩ0.56
L159 µH – 238 mH0.47227 mH – 7.95 H-7.29 H – 143.23 H-
C106 nF – 159 µF0.123.178 nF – 111 nF0.39176 pF – 3.47 nF0.1
10kR1 Ω – 900 Ω0.71500 Ω – 50 kΩ0.1210 kΩ – 10 MΩ2.49
L25.9 µH – 23.8 mH0.5722.6 mH – 795 mH1.81729 mH – 14.3 H-
C10.6 nF – 15.9 µF0.94317.8 pF – 11.1 nF0.417.6 pF – 347 pF0.22
100kR1 Ω – 900 Ω0.47500 Ω – 50 kΩ0.8710 kΩ – 10 MΩ14
L2.59 µH – 2.38 mH0.712.26 mH – 79.6 mH4.872 mH – 1.43 H-
C1.06 nF – 1.59 µF0.1731.78 pF - 1.11 nF1.81.76 pF- 34.7 pF5.5