[SI-LIST] Re: Board-to-board connectors without reference planes?
- From: steve weir <weirsi@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Wed, 04 Jun 2014 13:47:54 -0700
Don't forget crosstalk.
Best Regards,
Steve
On 6/4/2014 1:02 PM, Orin Laney wrote:
> LAN cable also works without a reference plane. Differential signals don't
> need them, but when reference planes are present they cooperate. The loop
> area principle applies between an unbalanced signal and an associated
> reference plane/ return path. For differential signals it applies between
> the conductors in the pair. If a reference plane is present, the image
> currents are likewise differential. The effects cancel in the far field for
> both the differential conductors and associated image currents.
>
> Orin
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
> Behalf Of ckrich_99@xxxxxxxxx (Redacted sender "ckrich_99@xxxxxxxxx" for
> DMARC)
> Sent: Wednesday, June 04, 2014 12:41 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Board-to-board connectors without reference planes?
>
> I know that high-speed signals must be routed with an adjacent reference
> plane so the current loop area is minimal. We’re always told not to cross
> plane splits on PCBs because this will cause SI/crosstalk and EMI issues.
> However, I’m working with a QSeven module, which plugs into an edge
> connector.  http://www.qseven-standard.org/ The QSeven connector supports
> very high-speed differential signals like Ethernet, USB, HDMI, LVDS and
> several single-ended buses. Once the module is plugged into a plastic
> connector, the signals pass through the connector into gold-plated discrete
> pins which are soldered to the baseboard. However, there’s no reference
> plane for these pins (for at least 6mm), and yet it works fine- how?
> I’ve had the same question about PCI Express connectors. They uses only
> differential-pairs so you can argue the diff-pairs use each other as
> “returns†if there’s no nearby plane. But QSeven also has high-speed
> single-ended signals.
> Thanks+ Regards,Richard
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