SNLA224A June   2014  â€“ 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

2 Theory of Operation for Power Over Coax

The purpose of a PoC network is to separate the high-speed data signal from the DC power signal. The high-speed signal consists of a high-speed forward channel carrying video and control data to the deserializer and a lower speed back channel carrying control data to the serializer. Figure 2-1 shows a high-level overview of how FPD-Link and DC power share a single coax cable. The DC power signal must be completely isolated from the DOUT pins of the serializer and the RIN pins of the deserializer. This is accomplished by placing AC coupling capacitors in line with the FPD-Link signal path, which blocks the DC signal and passes the forward and back channel data signals. A simple capacitor can work for this since it has very low impedance over the forward and back channel frequency and is an open circuit at DC.

The PoC network is a type of low pass filter circuit that is designed to pass the transmitted DC signal with minimal interference on the high-speed AC signal. For this low pass filter circuit to not interfere with the high-speed signal, the circuit needs to have an impedance much larger than the characteristic impedance of the channel. It is recommended that an impedance of 1 kΩ be met over the entire FPD-Link operational frequency band.

GUID-20230712-SS0I-ZC7T-JTRJ-BWDGJTZLNLZL-low.svg Figure 2-1 Concept for Power Over Coax