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Original question:

SN75LVPE4410: PCIe CLKREQ Question

SN75LVPE4410: what is the function of reg_06 Register drv_eq_en_override ?

zack yang
Prodigy 10 points
Part Number: SN75LVPE4410

what is the function of "drv_eq_en_override"   Enable overrides for driver and equalizer enables  ?  

Did i enable it or disable it ?

reg_06 Register 

  • TI__Mastermind 20901 points

    Hi Zack,

    The drv_eq_en_override bit of Channel Register 0x6 enables bits 4:2 of this register to be overridden, if desired.

    Most applications do not require drv_eq_en_override to be enabled, so I would suggest not enabling it (keep at Reset value 1b0).

    Best,
    David

  • Prodigy 10 points

    Hi David,

    Thanks for your reply.

    I find if I set all the bits 2~5 to bit1 and keep all other registers the same. I find the amplitude of the output waveform increased.

    Did these observation meet your expectation？

    big amplitude is better for my application.

    Could you help explain a little about bit 2~5 function? 

    Thanks! 

     

  • in reply to zack yang
    TI__Mastermind 20901 points

    Hi Zack,

    The suggested programming sequence for the device would be to adjust CTLE Gain, CTLE DC Gain, and VOD levels as suggested in the SN75LVPE4410 Programming Guide.. When adjusting these settings, do you notice increased output amplitude in your application? At what point is the amplitude being measured?

    Please note the SN75LVPE4410 data sheet Section 6.8 for typical characteristics of CTLE / EQ Index.

    Best,
    David

  • in reply to David Waier
    Prodigy 10 points

    Hi David

    1.the measure point at TXN TXP after the AC couple Cap (differential probe).

    2.  use I2C mode , setting the CTLE Gain index 0, CTLE DC Gain +3.5dB, and VOD levels 0dB，setting reg06 bits 2~5 to bit1 I did saw the amplitude increased in waveform .

    3. But use pin-mode, setting CTLE Gain index 0, CTLE DC Gain +3.5dB, I find the amplitude is smaller than step 2.  Do you known why?

    Best,

    Zack

  • in reply to zack yang
    TI__Mastermind 20901 points

    Hi Zack,

    The register bits 2-5 are set to control some internal drivers of the device, which could slightly increase amplitude of the output at the device.

    My suggestion is to increase CTLE Gain index to increase the amplitude level at the output of the device in your application.

    Best,
    David