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DS64MB201 - DeEmphasis setting

Kawai
Guru 19785 points


Hi Team,

Our customer uses this device, they have question about the DEM setting.

[Question]
What does bit7 "DEM Type(Compatibility / Enhanced) " mean ? What is it for ?

[Question]
If you just change bit7 of the DEM control register, is the DEM Gain stay same ?
For example, Does ADR 0x18 = 0x88 and ADR 0x18 = 0x08 have the same Gain setting ?

* We understand the recommended setting is the only value listed in the Registe map.
  We are asking because our customer is currently having some problem in the output.

http://e2e.ti.com/support/interface/high_speed_interface/f/138/t/307798.aspx 

Best Regards,
Kawai

  • 0
    TI__Intellectual 1705 points

    Hi,

    The driver de-emphasis DEM is an RC filter to improve the eye after the channel loss.

    The bit 7 is to enhance / improve the signal at the higher data rate by reducing the DEM pulse width.This helps to improve the eye for the high data rate signal (6Gbps). For low data rate signal 3Gbps, the bit would not help to enhance the eye.

    There is no gain/boost on the output driver with de-emphasis and the DEM level is the same for the compatability or enhanced setting.

    Regards,

    Michael