ZHCSSH5A August   2023  – December 2024 LOG200

PRODMIX  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 High Speed, Logarithmic Current-to-Voltage Conversion
      2. 6.3.2 Voltage and Current References
      3. 6.3.3 Adaptive Photodiode Bias
      4. 6.3.4 Auxiliary Operational Amplifier
    4. 6.4 Device Functional Modes
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Logarithmic Transfer Function
        1. 7.1.1.1 Logarithmic Conformity Error
        2. 7.1.1.2 Error Analysis Example
    2. 7.2 Typical Application
      1. 7.2.1 Optical Current Sensing
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
        3. 7.2.1.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 第三方产品免责声明
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 接收文档更新通知
    4. 8.4 支持资源
    5. 8.5 Trademarks
    6. 8.6 静电放电警告
    7. 8.7 术语表
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

封装选项

请参考 PDF 数据表获取器件具体的封装图。

机械数据 (封装 | 引脚)
  • RGT|16
散热焊盘机械数据 (封装 | 引脚)
订购信息

7.1.1.2 Error Analysis Example

For an illustration of typical system error for a LOG200 implementation, consider the example use case defined by the following conditions:

Table 7-1 Example Design Parameters
PARAMETER SYMBOL EXAMPLE VALUE
Maximum input current Imax 200µA
Minimum input current Imin 10nA
Output reference voltage VREF REF165 (1.65V)
Input reference current II2 IREF (1µA)
Supply voltage VS 10V (±5V)

Table 7-2lists the major error sources, and the typical values of each under the provided conditions. Typical values are generally the sum of the mean value and one standard deviation. Calculations using these typical values tend to be conservative, as the summation of uncorrelated errors tends to result in a larger compounded total predicted error than the actual total error observed in a real system.

Table 7-2 Example Error Sources
PARAMETER SYMBOL TYPICAL VALUE
IREF reference current error IREF_error 0.3%
REF165 reference error REF165error 0.06%
Scaling factor error Kerror 0.15%
Logarithmic conformity error LCE 0.05%
Logarithmic amplifier output offset error VOSO 1.3mV

These error terms are used to calculate actual values, as per the following equations:

Equation 8. I R E F _   a c t u a l = I R E F × 1 – I R E F _ e r r o r = 1 µ A × 1 – 0.00 3 = 0.997 µ A
Equation 9. V R E F _   a c t u a l = V R E F 165 × 1 + R E F 165 e r r o r = 1.65 V × 1 + 0.00 06 = 1.65099 V
Equation 10. K a c t u a l = K × 1 + K e r r o r = 250 m V d e c × 1 + 0.00 15 = 250. 375 m V d e c

Begin error analysis by solving for the nominal output voltage at the minimum and maximum currents, without considering error terms. The results are then used to approximate the contribution of the logarithmic conformity error, in mV.

Equation 11. V L O G _ nominal _ atIm i n = K × log 10 ⁡ I m i n I R E F + V R E F = 250 m V d e c × log 10 ⁡ 10 n A 1 µ A + 1.65 V = 1.15 V
Equation 12. V L O G _ nominal _ atIm a x = K × log 10 ⁡ I m a x I R E F + V R E F = 250 m V d e c × log 10 ⁡ 20 0 µ A 1 µ A + 1.65 V = 2.2253 V
Equation 13. L C E atIm i n = L C E × V L O G _ nominal _ atIm i n – V R E F = – 0.0005 × 1. 15 V – 1.65 V = 0.25 m V
Equation 14. L C E atIm a x = L C E × V L O G _ nominal _ atIm a x – V R E F = 0.0005 × 2. 2253 V – 1.65 V = 0.288 m V

Repeat this exercise, taking into account typical error values as previously calculated, and then determine the difference of the results to calculate the output error at each current level.

Equation 15. V L O G _ a c t u a l _ atIm i n = K a c t u a l × log 10 ⁡ I m i n I R E F _ a c t u a l + V R E F _ a c t u a l + V O S O + L C E atImin = 1.15 21 V
Equation 16. V L O G _ a c t u a l _ atIm a x = K a c t u a l × log 10 ⁡ I m a x I R E F _ a c t u a l + V R E F _ a c t u a l + V O S O + L C E atImax = 2.2290 V
Equation 17. V L O G _ e r r o r _ atIm i n = V L O G _ a c t u a l _ atIm i n – V L O G _ nominal _ atIm i n = 2.117 m V
Equation 18. V L O G _ e r r o r _ atIm a x = V L O G _ a c t u a l _ atIm a x – V L O G _ nominal _ atIm a x = 3.767 m V

The output error at a given current level is then expressed as a percentage of the full-scale range as per Equation 19 and Equation 20:

Equation 19. E R R O R f u l l _ s c a l e _ atIm i n = V L O G _ e r r o r _ atIm i n V L O G _ nominal _ atIm a x – V L O G _ nominal _ atIm i n = 0.197 %
Equation 20. E R R O R f u l l _ s c a l e _ atIm a x = V L O G _ e r r o r _ atIm a x V L O G _ nominal _ atIm a x – V L O G _ nominal _ atIm i n = 0.350 %