SNOSB28H August   2010  – October 2026 LMP8640 , LMP8640HV

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics 2.7V
    6. 6.6 Electrical Characteristics 5 V
    7. 6.7 Electrical Characteristics 12V
    8. 6.8 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Selection of Sense Resistor
        1. 7.3.1.1 Resistor Power Rating and Thermal Issues
        2. 7.3.1.2 Using PCB Trace as a Sense Resistor
      2. 7.3.2 Sense Line Inputs
      3. 7.3.3 Effects of Series Resistance on Sense Lines
    4. 7.4 Device Functional Modes
      1. 7.4.1 Bias Current at Low Common Mode Voltage
      2. 7.4.2 Applying Input Voltage With No Supply Voltage
      3. 7.4.3 Driving an ADC
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Design Procedure
        1. 8.2.2.1 First Step – LMP8640 or LMP8640HV Selection
        2. 8.2.2.2 Second Step – Gain Option Selection
        3. 8.2.2.3 Third Step – Shunt Resistor Selection
      3. 8.2.3 Application Curve
    3. 8.3 What to Do and What Not to Do
    4. 8.4 Power Supply Recommendations
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
      2. 8.5.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Development Support
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

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8.2.2.3 Third Step – Shunt Resistor Selection

At this point an error budget calculation, considering the calibration of the Gain, Offset, CMRR, and PSRR, helps in the selection of the shunt resistor. In the table below the contribution of each error source is calculated considering the values of the Electrical Characteristics table at 5 V supply.

Table 8-2 Resolution Calculation
ERROR SOURCERS = 4.1 mΩRS = 8.1 mΩ
CMRR calibrated at mid VCM range77.9 µV77.9 µV
PSRR calibrated at 5 V8.9 µV8.9 µV
Total error (squared sum of contribution)78 µV78 µV
Resolution (Total error / RS)19.2 mA9.6 mA
Table 8-3 Accuracy Calculation
ERROR SOURCERS = 4.1 mΩRS = 8.1 mΩ
Tc Vos182 µV182 µV
Noise216 µV216 µV
Gain drift75.2 µV151 µV
Total error (squared sum of contribution)293 µV320 µV
Accuracy 100×(Max_VSENSE / Total Error)0.7%0.4%

From the tables above is clear that the 8.2 mΩ shunt resistor allows the respect of the project constraints. The power burned on the Shunt is 820 mW at 10 A.