SNOSB29H November   2009  – May 2022 LMP8645 , LMP8645HV

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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 2.7-V Electrical Characteristics
    6. 6.6 5-V Electrical Characteristics
    7. 6.7 12-V Electrical Characteristics
    8. 6.8 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
      1. 7.1.1 Theory of Operation
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Driving ADC
      2. 7.3.2 Applying Input Voltage With No Supply Voltage
    4. 7.4 Device Functional Modes
      1. 7.4.1 Selection of the Gain Resistor
      2. 7.4.2 Gain Range Limitations
        1. 7.4.2.1 Range 1: VCM is –2 V to 1.8 V
        2. 7.4.2.2 Range 2: VCM is 1.8 V to VS
        3. 7.4.2.3 Range 3: VCM is greater than VS
      3. 7.4.3 Selection of Sense Resistor
        1. 7.4.3.1 Resistor Power Rating and Thermal Issues
        2. 7.4.3.2 Using PCB Trace as a Sense Resistor
      4. 7.4.4 Sense Line Inputs
        1. 7.4.4.1 Effects of Series Resistance on Sense Lines
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Typical Current Monitor Application
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
      2. 8.2.2 High Brightness LED Driver
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Support Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.1.1 Design Requirements

In this example, the LMP8645 is used to monitor the supply current of an active device (Refer to Figure 8-1). The LMP8645 supply voltage is 5 V and the active device is supplied with 12 V. The maximum load current is 1 A.

The LMP8645 will operate in all 3 ranges: in Range 1 when turning on the power of the active device (rising from 0 V to 12 V), while briefly passing through Range 2 as the load supply rises, and finally into Range 3 for normal load operation.

Because the purpose of the application is monitor the current of the active device in any operating condition (power on, normal operation, fault, and so forth), the gain resistor will be selected according to Range 1, the range that puts the most constraints to the maximum output voltage swing of the LMP8645.