SNLA475 October   2024 DS250DF410 , DS250DF810 , DS280BR810 , DS280BR820 , DS280DF810 , DS280MB810 , DS560MB410

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Codesign: 25GbE 4-Channel Retimer or Redriver with Crosspoint
    1. 2.1 DS250DF410 Retimer Overview
    2. 2.2 DS560MB410 Redriver Overview
    3. 2.3 Pin Comparison Table
    4. 2.4 Codesign Schematic Example
    5. 2.5 Notable Codesign Elements
      1. 2.5.1 Calibration Clock
      2. 2.5.2 SMBus Address
      3. 2.5.3 SMBus Controller Mode
      4. 2.5.4 SMBus Pull-Up Resistors
      5. 2.5.5 Interrupt Output
      6. 2.5.6 Mux Select Inputs
  6. 3Codesign: 25GbE 8-Channel Retimer or Redriver with Crosspoint
    1. 3.1 DS250DF810 and DS280DF810 Retimers Overview
    2. 3.2 DS280BR810, DS280BR820, and DS280MB810 Redrivers Overview
    3. 3.3 Pin Comparison Table
    4. 3.4 Codesign Schematic Example
    5. 3.5 Notable Codesign Elements
      1. 3.5.1 AC Coupling
      2. 3.5.2 Calibration Clock
      3. 3.5.3 SMBus Address
      4. 3.5.4 SMBus Controller Mode
      5. 3.5.5 SMBus Pull-Up Resistors
      6. 3.5.6 Interrupt Output
      7. 3.5.7 Mux Select Inputs
  7. 4Summary
  8. 5References

3.5.7 Mux Select Inputs

DS280MB810 includes mux select inputs on pins E2 (MUXSEL0) and E14 (MUXSEL1). MUXSEL0 controls the crosspoint for channels 0–1 and 4–5, and MUXSEL1 controls the crosspoint for channels 2–3 and 6–7. The crosspoint can also be controlled entirely via SMBus register writes.

There are 2 options regarding mux select input connections to DS280MB810 within this codesign example.

  1. Populate R6 and R7 with 0Ω resistors and depopulate R11 and R12. This allows an external device to control the crosspoint via LVCMOS voltage level inputs.
  2. Populate R11 and R12 with 1kΩ resistors and depopulate R6 and R7. This option is most useful if the mux select inputs are unused.

DS2x0DF810 and DS280BR8x0 do not include mux select inputs. The crosspoint on DS2x0DF810 is controlled entirely via SMBus register writes. DS280BR8x0 does not include any crosspoint capability. On DS2x0DF810 and DS280BR8x0, pins E2 (TEST0) and E14 (TEST1) are reserved TI test pins which can be left floating, tied to GND, or connected to a 2.5V output. This codesign example includes 1kΩ pull-downs to GND when R11 and R12 are populated and R6 and R7 are depopulated.