[SI-LIST] Re: impedance determination of a perticular interface.....
- From: bala <balaseven@xxxxxxxxx>
- To: malli.1729@xxxxxxxxx
- Date: Thu, 18 Sep 2014 10:25:02 +0530
50 ohm is the compromise between power handling(low impedance) and low
insertion loss( high impedance).
Regards
bala
On 18 Sep 2014 10:09, "Mallikarjun K" <malli.1729@xxxxxxxxx> wrote:
> Hi,
> I have seen specifying routing impedance of interfaces from Manufacturers
> like for
>
> USB Differential impedance of 90 ohms
>
> DDR2 Single ended impedance 50-60 Ohms, Differential impedance - 100-120
> Ohms.
>
> If not specified , generally we will try to take it as 50 Ohms.
>
> Based on this interface impedance levels, we will design corresponding
> Stripline/microstrip lines parameters like Height above reference plane and
> width to give required characterstic impedance..
>
> What drives these characteristic impedance values? Whether the drivers
> output impedance has any affect on this...?
>
> If route a 50Ohms interface with 20 Ohms impedance what are the impacts?
>
> In few papers, i have read that intentionally designers will route with
> higher/lower (not sure ) impedance for crosstalk reduction. Is this
> impedance has any relationship with the impedance....
>
>
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