SNLA224A June   2014  – January 2024 DS90UB913A-Q1 , DS90UB954-Q1 , DS90UB960-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Theory of Operation for Power Over Coax
    1. 2.1 Inductor Characteristics
    2. 2.2 Capacitor Characteristics
    3. 2.3 Ferrite Bead Characteristics
  6. 3Design Considerations
    1. 3.1 Frequency Range
    2. 3.2 Power Considerations
    3. 3.3 Inductor Size Considerations
    4. 3.4 Layout Considerations
  7. 4FPD-Link PoC Requirements
    1. 4.1 Channel Requirements
    2. 4.2 PoC Noise Requirements
      1. 4.2.1 VPoC Noise and Pulse
      2. 4.2.2 RIN+ Noise
      3. 4.2.3 Causes of PoC Noise
      4. 4.2.4 Noise Measurement Best Practices
      5. 4.2.5 Reducing Effects of PoC Noise
  8. 5TI Recommended PoC Networks
    1. 5.1 PoC Network From FPD-Link III Data Sheet
    2. 5.2 Murata Networks
      1. 5.2.1 Murata Network 1
      2. 5.2.2 Murata Network 2
      3. 5.2.3 Murata Network 3
    3. 5.3 TDK Networks
      1. 5.3.1 TDK Network 1
      2. 5.3.2 TDK Network 2
      3. 5.3.3 TDK Network 3
      4. 5.3.4 TDK Network 4
      5. 5.3.5 TDK Network 5
      6. 5.3.6 TDK Network 6
      7. 5.3.7 TDK Network 7
      8. 5.3.8 TDK Network 8
    4. 5.4 Coilcraft Networks
      1. 5.4.1 Coilcraft Network 1
      2. 5.4.2 Coilcraft Network 2
      3. 5.4.3 Coilcraft Network 3
      4. 5.4.4 Coilcraft Network 4
  9. 6Summary
  10. 7References
  11. 8Revision History

3.3 Inductor Size Considerations

Although not required for functionality, some systems have size constraints that must be considered when designing a PoC network. The values of the inductors used are based on the impedance and filtering needs of the system, but the physical size of the inductors is dependent on the ability of the device core to sustain the magnetic field. Physically smaller inductors have lower saturation currents and limit the current rating of the PoC network. One way to safely use an inductor with a lower saturation current is to reduce the current requirement of the circuit by increasing the voltage being carried by the coax cable. For example, if the camera or sensor requires 1.5 W and a PoC voltage of 5 V is used, a current of 300 mA must be supported. However, if a PoC voltage of 12 V is used, a current of only 125 mA must be supported. The lower current requirement allows for an inductor with a lower saturation current and potentially smaller footprint to be used.