SDAA081 September   2025 DP83825I

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Troubleshooting the Application
    1. 2.1 Schematic Checklist
    2. 2.2 Device Health Checks
      1. 2.2.1 Voltage Checks
      2. 2.2.2 Probe the RESET_N Signal
      3. 2.2.3 Probe RBIAS
      4. 2.2.4 Probe the XI Clock
      5. 2.2.5 Probe the Strap Pins During Initialization
      6. 2.2.6 Probe the Serial Management Interface (MDC, MDIO)
        1. 2.2.6.1 Read and Check Register Values
    3. 2.3 MDI Health Checks
      1. 2.3.1 Magnetics
      2. 2.3.2 Probe the MDI Signals
      3. 2.3.3 Check the Link Quality
      4. 2.3.4 Compliance
    4. 2.4 RMII Health Check
    5. 2.5 Loopback and PRBS
      1. 2.5.1 Loopback Modes
      2. 2.5.2 Transmitting and Receiving Packets with the MAC
      3. 2.5.3 Transmitting and Receiving Packets with BIST
  6. 3Summary
  7. 4References

2.3.1 Magnetics

The following guidelines are the main specifications to reference for compatible magnetics:

Table 2-5 Magnetic Isolation Specifications
ParameterTest ConditionsTYPUNIT
Turns Ratio±2% Tolerance1:1-
Insertion Loss1-100MHz-1dB
Return Loss1-30MHz-16dB
30-60MHz-10dB
60-80MHz-7.5dB
Differential to Common Mode Rejection Ratio1-50MHz-61dB
50MHz-33dB
150MHz-25dB
Crosstalk30MHz-45dB
60MHz-39dB
IsolationHPOT1500Vrms

If these exact requirements cannot be met, the following allowances can be made:

  • Turns ratio: 3% tolerance is good
  • Inductance: High inductance is preferred, typically around 350μH
  • Insertion loss: -1dB or closer to 0dB
  • Return loss: Meets or exceeds values in Table 2-5. For example -16dB, -17dB, … is good at 1-30MHz