[SI-LIST] Re: ECL or LVDS?
- From: Bill.Cohen@xxxxxxxxxxxxxxxx
- To: jtalavera@xxxxxx
- Date: Fri, 15 Nov 2002 15:13:21 -0500
Hi Juan,
From my perspective they're about the same. Both use 50 ohm (100ohm)
differential terminations. Differences occur in the power supplies. PECL
(positive ECL) generally use 3.3V power supplies. CMOS LVDS usually use
2.5V power supplies.
For slower speeds LVDS might be able to be designed with less power for the
receiver. The drivers will generally use the same power. PECL differential
voltages are generally bigger than LVDS which would consume more DC power.
Newer PECL parts use lower swing to conserve on the power.
To implement the full LVDS specification the receiver needs to rail-to-rail
common mode. This may burn more power to achieve than the PECL receiver
which has a narrower common mode range. But this is just splitting hairs.
Generally now we use CML transceivers for our fastest interfaces. We can
just go faster in CMOS if we aren't limited to an LVDS or PECL interface.
This is because our fastest CMOS technologies are all low voltage. They
just can't operate at 2.5V or 3.3V. So if we run a 1.5V CML interface we
can use the transistors with the highest bandwidth.
--------------------------------------------------------------
| Bill Cohen
| Toshiba America Electronic Components, Mixed Signal Design
| email: wcohen@xxxxxxxx
| office: (508) 486-1031 fax: (508) 481-8828
--------------------------------------------------------------
"Juan Manuel"
<jtalavera@xxxxxx> To: "si list"
<si-list@xxxxxxxxxxxxx>
Sent by: cc:
si-list-bounce@fre Subject: [SI-LIST] ECL or
LVDS?
elists.org
11/15/2002 02:34
PM
Please respond to
jtalavera
Hello everybody,
I'm looking for the best logic system for differential signaling. I was
looking in internet and, depending of the manufacturer, I've found studies
where ECL is the best system ( less power, more power ) and LVDS is not too
good( slow and high consumption ) and other studies say the opposite. So,
how is the situation?
Please, if you know something and you are not an onsemi or national semi
employee, write me.
Thank you, beforehand
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