SNVS829F March   1999  – May 2026 LMP8480 , LMP8481

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  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
    6. 6.6 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
      1. 7.1.1 Theory of Operation
    2. 7.2 Functional Block Diagrams
    3. 7.3 Feature Description
      1. 7.3.1  Basic Connections
      2. 7.3.2  Selection of the Sense Resistor
      3. 7.3.3  Using PCB Traces as Sense Resistors
      4. 7.3.4  VREFA and VREFB Pins (LMP8481 Only)
        1. 7.3.4.1 One-to-One (1:1) Reference Input
        2. 7.3.4.2 Setting Output to One-Half VCC or external VREF
      5. 7.3.5  Reference Input Voltage Limits (LMP8481 Only)
      6. 7.3.6  Low-Side Current Sensing
      7. 7.3.7  Input Series Resistance
      8. 7.3.8  Minimum Output Voltage
      9. 7.3.9  Swinging Output Below Ground
      10. 7.3.10 Maximum Output Voltage
    4. 7.4 Device Functional Modes
      1. 7.4.1 Unidirectional vs Bidirectional Operation
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Input Common-Mode and Differential Voltage Range
    2. 8.2 Typical Applications
      1. 8.2.1 Unidirectional Application With the LMP8480
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curve
      2. 8.2.2 Bidirectional Current Sensing Using the LMP8481
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curve
      3. 8.2.3 Typical Application With a Resistive Divider
  10. 9 Power Supply Recommendations
    1. 9.1 Power Supply Decoupling
  11. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  12. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  13. 12Revision History
  14. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.3.9 Swinging Output Below Ground

If a negative supply is available, a pulldown resistor can be added from the output to the negative voltage to allow the output to swing a few millivolts below ground. Adding a pulldown resistor allows the ADC to resolve true zero and recover codes that normally are lost to the negative output saturation limit.

LMP8480 LMP8481 Output Pulldown Resistor ExampleFigure 7-10 Output Pulldown Resistor Example

A minimum of 50 µA must be sourced (pulled) from the output to a negative voltage. The pulldown resistor can be calculated from:

Equation 8. RPD = –VS / 50 µA

For example, if a –5-V supply is available, use a pulldown resistor of 5 V / 50 µA = 100 kΩ. Adding this resistor allows the output to swing to approximately 10 mV below ground.

This technique can also reduce the maximum positive swing voltage. Do not forget to include the parallel loading effects of the pulldown any output load. Exceeding –100 mV on the output is not recommended. Source currents greater than 100 µA must be avoided to prevent self-heating at high-supply voltages. Pulldown resistor values must not be so low as to heavily load the output during positive output excursions. This mode of operation is not directly specified and is not ensured.