TIDUEB2A July   2022  – July 2022

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1  Power Multiplexing Circuit Design Parameters
      2. 2.2.2  Input Connections and Filter
      3. 2.2.3  Reverse Polarity Protection
      4. 2.2.4  Battery Charger Input
      5. 2.2.5  Battery Ideal Diode-OR
      6. 2.2.6  Input and Battery Switchover Mechanics
      7. 2.2.7  LM74800 (U1) HGATE
      8. 2.2.8  Battery LM74800 HGATE
      9. 2.2.9  BQ25731 Design Considerations
      10. 2.2.10 BQ25731 Component Selection
      11. 2.2.11 ILIM Circuit
      12. 2.2.12 MCU and I2C Bus Design Considerations
      13. 2.2.13 MSP430FR2475
      14. 2.2.14 I2C Bus Overview
      15. 2.2.15 MSP430 Connectors
      16. 2.2.16 MSP430 Power Supply
      17. 2.2.17 Sensing Circuits
      18. 2.2.18 Current Sensing
      19. 2.2.19 Voltage Sensing
      20. 2.2.20 Input Comparators
      21. 2.2.21 Software Flow Chart
    3. 2.3 Highlighted Products
      1. 2.3.1 BQ25731
      2. 2.3.2 LM7480-Q1
      3. 2.3.3 LM74700-Q1
      4. 2.3.4 MSP430FR2475
      5. 2.3.5 PCA9546A
  8. 3Hardware, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Test Setup
    3. 3.3 Test Results
      1. 3.3.1 Adaptive Charge Current Limiting
      2. 3.3.2 Battery ORing System
      3. 3.3.3 Circuit Switchover From Adapter to Battery
  9. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
    2. 4.2 Documentation Support
    3. 4.3 Support Resources
    4. 4.4 Trademarks
  10. 5Revision History

1 System Description

All portable equipment carried in aircrafts – including life-critical medical equipment such as portable ventilators, electrocardiogram devices (ECGs), and continuous positive-airway-pressure (CPAP) machines – are subjected to safety restrictions implemented by the Transportation Security Administration (TSA). Lithium batteries with more than 100 watt-hours (Wh) are generally not permitted in carry-on luggage, and any exceptions to this rule lie at the discretion of airlines and require prior approval. This disruption is not ideal for passengers who require these devices out of medical necessity. With the capabilities of Li-ion battery charging technology today, medical instrument manufacturers can alleviate this patient burden. To satisfy travel restrictions while also doubling the backup time of the equipment, two 100-Wh batteries can be implemented in the system design. This configuration will also require fewer spare batteries, increasing convenience for the end user during travel. This design guide details the implementation of two BQ25731 chargers managed by an onboard MCU to achieve these requirements for airline travel.