SLVAF74 July   2021 TPS2372 , TPS2373 , TPS23730 , TPS23731 , TPS23734 , TPS2375 , TPS2375-1 , TPS23750 , TPS23751 , TPS23752 , TPS23753A , TPS23754 , TPS23754-1 , TPS23755 , TPS23756 , TPS23757 , TPS23758 , TPS2376 , TPS2376-H , TPS2377 , TPS2377-1 , TPS23770 , TPS2378 , TPS2379

 

  1.   Trademarks
  2. 1Introduction
  3. 2Preparation and Measurement Techniques
    1. 2.1 Important PoE Signals
    2. 2.2 Lab Equipment
    3. 2.3 Measurement Techniques
    4. 2.4 Board Preparation
  4. 3Narrowing Down the Problem Area
    1. 3.1 Schematic Areas
    2. 3.2 Narrowing Down the Area On Board
  5. 4Common Issues
  6. 5Conclusion

2.4 Board Preparation

When prepping a board for debugging, install a wire for RTN, primary ground, so that many oscilloscope probe ground clips can connect to it easily. Do this for both primary ground and secondary ground. Potentially all four probes of an oscilloscope could be connected to primary ground, so make the wire long enough for all four to connect. However, a wire is essentially an antenna, so do not make it excessively long. It should not exceed the length of 5 milimeters, as a general rule. Other signals to put wires on are VDD, VC, and Vout. A wire can connect to these signals because these voltages should be steady and are relatively high voltage (as in connecting a wire to them for the scope probe should not introduce a significant amount of noise to the measurement versus directly connecting the probe to the board). Trying to hold more than two oscilloscope probes and operate the power supplies and take good measurements can be difficult, so it is good to have wire connections with wires, when able. Taking these measures provide a sufficient start for debugging.