SLVAE30E February   2021  – March 2021 TPS1H000-Q1 , TPS1H100-Q1 , TPS1H200A-Q1 , TPS1HA08-Q1 , TPS25200-Q1 , TPS27S100 , TPS2H000-Q1 , TPS2H160-Q1 , TPS2HB16-Q1 , TPS2HB35-Q1 , TPS2HB50-Q1 , TPS4H000-Q1 , TPS4H160-Q1

 

  1.   Trademarks
  2. 1Introduction
  3. 2Driving Resistive Loads
    1. 2.1 Background
    2. 2.2 Application Example
    3. 2.3 Why Use a Smart High Side Switch?
      1. 2.3.1 Accurate Current Sensing
      2. 2.3.2 Adjustable Current Limiting
    4. 2.4 Selecting the Right Smart High Side Switch
      1. 2.4.1 Power Dissipation Calculation
      2. 2.4.2 PWM and Switching Loss
  4. 3Driving Capacitive Loads
    1. 3.1 Background
    2. 3.2 Application Examples
    3. 3.3 Why Use a Smart High Side Switch?
      1. 3.3.1 Capacitive Load Charging
      2. 3.3.2 Inrush Current Mitigation
        1. 3.3.2.1 Capacitor Charging Time
      3. 3.3.3 Thermal Dissipation
      4. 3.3.4 Junction Temperature During Capacitive Inrush
      5. 3.3.5 Over Temperature Shutdown
      6. 3.3.6 Selecting the Correct Smart High Side Switch
  5. 4Driving Inductive Loads
    1. 4.1 Background
    2. 4.2 Application Examples
    3. 4.3 Why Use a Smart High Side Switch?
    4. 4.4 Turn-On Phase
    5. 4.5 Turn-Off Phase
      1. 4.5.1 Demagnetization Time
      2. 4.5.2 Instantaneous Power Losses During Demagnetization
      3. 4.5.3 Total Energy Dissipated During Demagnetization
      4. 4.5.4 Measurement Accuracy
      5. 4.5.5 Application Example
      6. 4.5.6 Calculations
      7. 4.5.7 Measurements
    6. 4.6 Selecting the Correct Smart High Side Switch
  6. 5Driving LED Loads
    1. 5.1 Background
    2. 5.2 Application Examples
    3. 5.3 LED Direct Drive
    4. 5.4 LED Modules
    5. 5.5 Why Use a Smart High Side Switch?
    6. 5.6 Open Load Detection
    7. 5.7 Load Current Sensing
    8. 5.8 Constant Current Source
      1. 5.8.1 Selecting the Correct Smart High Side Switch
  7. 6Appendix
    1. 6.1 Transient Thermal Impedance Data
    2. 6.2 Demagnitization Energy Capability Data
  8. 7References
  9. 8Revision History

1 Introduction

Often in systems central modules provide power to off-board loads in a number of different form factors. This occurs in situations such as a central module powering an automotive head-light, a PLC system powering a robotic arm, and a household appliance powering the indicators on the front panel. Situations where off-board loads must be driven are common in the vast majority of electrical systems and introduce specific challenges to the system designer. While it can be simple to switch enough DC power to meet the system requirements, it is much more challenging to ensure robust protection against short circuits and open circuits, provide fault indication, power up the load quickly, and enable predictive maintenance. These additional features are being increasingly requested by designs, so an engineer needs to select an output topology that enables this functionality. The best way to accomplish this is to use a Smart High Side Switch which can reliably drive off-board loads and enable numerous diagnostic and failure prevention mechanisms.

Not all off-board loads are the same. Each load profile will interact differently with the Smart High Side Switch and require different considerations to ensure robust protection. Whether the load is resistive, capacitive, inductive, or does not fall neatly into one of those categories such as LEDs will change how driving the load must be approached and designed. A proper output power protection designer needs to understand what load profile will be expected,and then understand how that impacts the design of the output stage. This document will analyze a few common load profiles and discuss the specific challenges and considerations for those loads. The load profiles that will be investigated in this document are:

  1. Section 2: Driving Resistive Loads
  2. Section 3: Driving Capacitive Loads
  3. Section 4: Driving Inductive Loads
  4. Section 5: Driving LED Loads

For each of these load types this document will give example applications with the given profile, discuss why a Smart High Side Switch offers advantages compared to traditional discrete solutions, go in depth on the technical challenges unique to that load type, and then offer guidelines for selecting the proper Smart High Side Switch for a given application.

Through a proper and thorough understanding of the impacts of a load profile on an output power stage it is possible to significantly improve functionality and reliability for a system. As designs continue to get smarter and more robust this understanding is critical for all designers.