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

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ
発注情報

7.4.3 Driving an ADC

The input stage of an Analog to Digital converter can be modeled with a resistor and a capacitance to ground. So if the voltage source does not have a low impedance, an error in amplitude measurement occurs. In this case, a buffer is needed to drive the ADC. LMP8640 and LMP8640HV have internal output buffer able to directly drive a capacitive load up to 30 pF, or, the input stage of an ADC. An external low pass RC filter is recommended to be added to the output of LMP8640 and LMP8640HV to reduce the noise and limit the bandwidth of the current sense measurement.

If the supply voltage of LMP8640 and LMP8640HV is higher than the ADC supply voltage, care must be taken to prevent LMP8640 and LMP8640HV output from over-driving the ADC input.

This can be accomplished with a series resistance (which must be present when driving a ADC) and a clamping diode to the ADCs power supply. The diode clamps the ADC input to a safe level. Do not completely rely on a calculated maximum output voltage. Transients or fault conditions outside the normal conditions area can cause the output to swing to a higher than expected voltage.