SNLA338A January   2020  – August 2022 DP83826E

 

  1.   KSZ8081MNX/RNB to DP83826 System Rollover
  2.   Trademarks
  3. 1Purpose
  4. 2Required Changes
    1. 2.1 Strap Resistor Value
    2. 2.2 External Capacitor on Pin 2
    3. 2.3 Duplex Strap on Pin 16 (DP83826 Basic Mode)
    4. 2.4 Selecting 10M with Auto-Negotiation Enabled (DP83826 Basic Mode)
    5. 2.5 Configuring LED_1 for Tx and Rx Activity for EtherCAT Slave (DP83826 Basic Mode)
    6. 2.6 Thermal Pad Adjustments in Layout
    7. 2.7 Physical Layer ID Register
  5. 3Potential Changes
    1. 3.1 MDIO Pull-Up Resistor on Pin 11
    2. 3.2 MDIO Register Writes
    3. 3.3 Capacitors on Center Tap of Magnetics
  6. 4Informational Changes
  7. 5Pinout Mapping
    1. 5.1 Pin Mapping
  8. 6DP83826 Strap Configurations
    1. 6.1 Bootstrap Configurations
  9. 7Revision History

2.1 Strap Resistor Value

The DP83826 supports either BASIC Mode or ENHANCED Mode. BASIC Mode supports the same bootstrap options as the KSZ8081. To set the DP83826 for BASIC Mode, pin 1, ModeSelect, must be tied to ground. In a KSZ8081 design, Pin 1 is already tied to GND, so there is no change needed to select the correct mode. To understand the difference between DP83826 BASIC Mode and ENHANCED Mode, refer to the DP83826 Datasheet.

Both devices use a 2-level strap that may require a pull-up or pull-down resistor. The table below shows the difference in pull-up and pull-down resistor values between the DP83826 and the KSZ8081. Refer to the TI Precision Labs Video 'How Do Ethernet bootstraps work?' to properly calculate the correct strap resistors.

Table 2-1 Strap Resistor Values
KSZ8081MNX/RNB DP83826
Pull-Up Resistor Value 4.7 kΩ 2.49 kΩ
Pull-Down Resistor Value 1.0 kΩ 2.49 kΩ

For specific strap options, please refer to the Appendix of this Application Note.