TIDUEP0 May   2020

 

  1.    Description
  2.    Resources
  3.    Features
  4.    Applications
  5. 1Design Images
  6. 2System Description
    1. 2.1 Key System Specifications
  7. 3System Overview
    1. 3.1 Block Diagram
    2. 3.2 Design Considerations
      1. 3.2.1 Small Compact Size
      2. 3.2.2 Transformer less Solution
    3. 3.3 Highlighted Products
      1. 3.3.1  TPD4E05U06 4-Channel Ultra-Low-Capacitance IEC ESD Protection Diode
      2. 3.3.2  TPD2EUSB30 2-Channel ESD Solution for SuperSpeed USB 3.0 Interface
      3. 3.3.3  2.3.3 HD3SS3220 10Gbps USB 3.1 USB Type-C 2:1 MUX With DRP Controller
      4. 3.3.4  TPS54218 2.95V to 6V Input, 2A Synchronous Step-Down SWIFT™ Converter
      5. 3.3.5  TPS54318 2.95V to 6V Input, 3A Synchronous Step-Down SWIFT™ Converter
      6. 3.3.6  CSD19538Q3A 100V, N ch NexFET MOSFET™, single SON3x3, 49mOhm
      7. 3.3.7  LM3488 2.97V to 40V Wide Vin Low-Side N-Channel Controller for Switching Regulators
      8. 3.3.8  TPS61178 20-V Fully Integrated Sync Boost with Load Disconnect
      9. 3.3.9  LMZM23601 36-V, 1-A Step-Down DC-DC Power Module in 3.8-mm × 3-mm Package
      10. 3.3.10 TPS7A39 Dual, 150mA, Wide-Vin, Positive and Negative Low-Dropout (LDO) Voltage Regulator
      11. 3.3.11 TPS74201 Single-output 1.5-A LDO regulator, adjustable (0.8V to 3.3V), any or no cap, programmable soft start
      12. 3.3.12 LP5910 300-mA low-noise low-IQ low-dropout (LDO) linear regulator
      13. 3.3.13 LP5907 250-mA ultra-low-noise low-IQ low-dropout (LDO) linear
      14. 3.3.14 INA231 28V, 16-bit, i2c output current/voltage/power monitor w/alert in wcsp
    4. 3.4 System Design Theory
      1. 3.4.1 Input Section
      2. 3.4.2 Designing of SEPIC based High Voltage Supply
        1. 3.4.2.1  Basic Operation Principle of SEPIC Converter
        2. 3.4.2.2  Design of Dual SEPIC Supply using uncoupled inductors
        3. 3.4.2.3  Duty Cycle
        4. 3.4.2.4  Inductor Selection
        5. 3.4.2.5  Power MOSFET Selection
        6. 3.4.2.6  Output Diode Selection
        7. 3.4.2.7  Coupling Capacitor Selection
        8. 3.4.2.8  Output Capacitor Selection
        9. 3.4.2.9  Input Capacitor Selection
        10. 3.4.2.10 Programming the Output Voltage
      3. 3.4.3 Designing the Low Voltage Power Supply
      4. 3.4.4 Designing the TPS54218 through Webench Power Designer
      5. 3.4.5 ± 5V Transmit Supply Generation
      6. 3.4.6 System Clock Synchronization
      7. 3.4.7 Power and data output connector
      8. 3.4.8 System Current and Power Monitoring
  8. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Testing and Results
      1. 4.1.1 Test Setup
      2. 4.1.2 Test Results
        1. 4.1.2.1 High Voltage Power Supply
        2. 4.1.2.2 Output Ripple Measurement
        3. 4.1.2.3 Load Transient Test
        4. 4.1.2.4 Noise Measurement
        5. 4.1.2.5 Thermal Performance
        6. 4.1.2.6 Low Voltage Power Supply
          1. 4.1.2.6.1 Thermal Performance
          2. 4.1.2.6.2 FX3 Supply
  9. 5Layout Guidelines
    1. 5.1 High-Voltage Supply Layout
    2. 5.2 USB Section Layout Guidelines
  10. 6Design Files
    1. 6.1 Schematics
    2. 6.2 Bill of Materials
    3. 6.3 PCB Layout Recommendations
      1. 6.3.1 Layout Prints
    4. 6.4 Altium Project
    5. 6.5 Gerber Files
    6. 6.6 Assembly Drawings
  11. 7Software Files
  12. 8Related Documentation
    1. 8.1 Trademarks
    2. 8.2 Third-Party Products Disclaimer
  13. 9About the Author

3.4.2.4 Inductor Selection

A good rule for determining the inductance is to allow the peak-to-peak ripple current to be approximately 40% of the maximum input current at the minimum input voltage. The ripple current flowing in equal value inductors L1 and L2 is given by:

Equation 3. TIDA-010057 EQ3_Peak_INDUCTOR.gif

The inductor values can be calculated by:

Equation 4. TIDA-010057 EQ4_L1.gif
Equation 5. TIDA-010057 EQ5_L2.gif

The inductor value chosen for L1 was 100uH and 1000uH for L2 for easier component selection and availability.

The fsw is the switching frequency and Dmax is the duty cycle at the minimum Vin. The peak current in the inductor, to ensure the inductor does not saturate, is given by:

Equation 6. TIDA-010057 EQ6_PeakL1.gif
Equation 7. TIDA-010057 EQ7_PeakL2.gif