Hello Praveen,
The answer to your question is dependent on the transmitter
implementation. For many current-mode designs the power is largely
independent of the de-emphasis setting since the TX is simply pushing a
fixed current through the channel or a shunt path. In some voltage mode
designs the power is lower with a higher de-emphasis setting. There may
also be some designs for which the reverse is true. So there is no general
rule and if you wish to optimize power in this way, you might try and get
details of the TX design from the IC vendor or do your own measurements of
the power consumption with different settings.
-Bill
On Mon, Mar 20, 2017 at 10:12 AM, Praveen Kumar <praveenkumardr@xxxxxxxxx>
wrote:
Hi experts,
Is there any advantage of choosing different de-emphasis in terms of Power
Saving, if you are free to choose any de-emphasis (-3.5dB or default
-6dB). This is in situations when the Eye is wide enough with either
de-emphaiss level but you want to choose that particular de-empahsis level
which will save you some power, If it does)
Or is it just attenuating (passive attenuator) the Transmitted signal (at
Tx) to different extent, so there is no power being saved or lost, be it
-3.5dB or -6dB or no de-emphasis at all. (Unlike in pre-empahsis where you
lose extra power if you choose to boost high frequency content by enabling
pre-emphasis)
Is there any Paper on this topic (PCIe Gen2 de-emphasis implementation and
its impact on total power)
Thank you,
Praveen
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