TIDUFA5 December   2024

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Small Compact Size
      2. 2.2.2 Transformerless Design
    3. 2.3 Highlighted Products
      1. 2.3.1  BQ25790 IIC Controlled, 1–4 Cell, 5A Buck-Boost Battery Charger
      2. 2.3.2  TPS3422 Low-Power, Push-Button Controllers With Configurable Delay
      3. 2.3.3  SN74LVC1G74 Single Positive-Edge-Triggered D-Type Flip-Flop With Clear and Preset
      4. 2.3.4  TPS259470 2.7V–23V, 5.5A, 28mΩ True Reverse Current Blocking eFuse
      5. 2.3.5  TPS54218 2.95V to 6V Input, 2A Synchronous Step-Down SWIFT Converter
      6. 2.3.6  TPS54318 2.95V to 6V Input, 3A Synchronous Step-Down SWIFT Converter
      7. 2.3.7  LM5158 2.2MHz, Wide VIN, 85V Output Boost, SEPIC, or Flyback Converter
      8. 2.3.8  TPS61178 20V Fully Integrated Sync Boost With Load Disconnect
      9. 2.3.9  LMZM23601 36V, 1A Step-Down DC-DC Power Module in 3.8mm × 3mm Package
      10. 2.3.10 TPS7A39 Dual, 150mA, Wide-VIN, Positive and Negative Low-Dropout (LDO) Voltage Regulator
      11. 2.3.11 TPS74401 3.0A, Ultra-LDO With Programmable Soft Start
      12. 2.3.12 TPS7A96 2A, Ultra-Low Noise, Ultra-high PSRR RF Voltage Regulator
      13. 2.3.13 LM3880 3-Rail Simple Power Sequencer With Fixed Time Delay
      14. 2.3.14 DAC53401 10-Bit, Voltage-Output DAC With Nonvolatile Memory
      15. 2.3.15 INA231 28V, 16-bit, I2C Output Current, Voltage, and Power Monitor With Alert in WCSP
  9. 3System Design Theory
    1. 3.1 Input Section
      1. 3.1.1 Buck-Boost Charger
      2. 3.1.2 Power On or Off
    2. 3.2 Designing SEPIC and Cuk Based High-Voltage Power Supply
      1. 3.2.1 Basic Operation Principle of SEPIC and Cuk Converters
      2. 3.2.2 Dual High-Voltage Power Supply Design Using Uncoupled Inductors With SEPIC and Cuk
        1. 3.2.2.1 Duty Cycle
        2. 3.2.2.2 Inductor Selection
        3. 3.2.2.3 Power MOSFET Verification
        4. 3.2.2.4 Output Diode Selection
        5. 3.2.2.5 Coupling Capacitor Selection
        6. 3.2.2.6 Output Capacitor Selection
        7. 3.2.2.7 Input Capacitor Selection
        8. 3.2.2.8 Programming the Output Voltage With Adjustable function
    3. 3.3 Designing the Low-Voltage Power Supply
      1. 3.3.1 Designing the TPS54218 Through WEBENCH Power Designer
      2. 3.3.2 ±5V Transmit Supply Generation
    4. 3.4 System Clock Synchronization
    5. 3.5 Power and Data Output Connector
    6. 3.6 System Current and Power Monitoring
  10. 4Hardware, Testing Requirements, and Test Results
    1. 4.1 Hardware Requirements
    2. 4.2 Test Setup
    3. 4.3 Test Results
      1. 4.3.1 Efficiency Test Result
      2. 4.3.2 Line Regulation Testing Result
      3. 4.3.3 Spectrum Test Result
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
      3. 5.1.3 PCB Layout Recommendations
        1. 5.1.3.1 High-Voltage Supply Layout
    2. 5.2 Tools and Software
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks

3.1.1 Buck-Boost Charger

The first stage uses a BQ25790 buck-boost charger. The charger uses a 1-cell Li-ion or Li-polymer battery. The chip also integrates a smart power path function which can keep the system operating even when the battery is completely discharged or removed. When the load power exceeds the input source rating or is removed, the battery goes into supplemental mode and prevents the input source from being overloaded and the system from crashing. In the absence of input sources, BQ25790 supports the USB On-the-Go (OTG) function, discharging the battery to generate an adjustable 2.8V–22V voltage on VBUS with a 10mV step size. This action is compliant to the USB PD 3.0 specification defined by the programmable power supply (PPS) feature and can charge an external device. Besides the I2C host-controlled charging mode, this charger also supports autonomous charging mode. After power up, the charging is enabled with default register settings. The device can complete a charging cycle without any software engagements. The BQ25790 detects battery voltage and charges the battery in different phases: trickle charging, pre-charging, constant current (CC) charging, and constant voltage (CV) charging. At the end of the charging cycle, the charger automatically terminates when the charge current is below a pre-set limit (termination current) in the constant voltage phase. When the full battery falls below the recharge threshold, the charger automatically starts another charging cycle.

TI uses autonomous mode to charge the battery but keeps the I2C interface in this reference design. The designer can configure the PROG pin of BQ25790 with a 4.7kΩ resistor to ground and set up a switching frequency to 750kHz and default charge current to 2A. Tie VAC1 and VAC2 to VBUS and connect ACDRV1 and ACDRV2 to GND since there is only one USB Type-C connector for the external adapter and no external ACFET-RBFET. Equation 1 shows the input current limit setting calculation.

Equation 1. I i n p u t _ l i m i t= V I L I M-10.8= V R E G N× R130 R128+ R130-10.8

The designer can update R128 and R130 to get to the expected current limit. In this reference design, the designer follows the EVM board to configure the current limit at 1.4A.