[SI-LIST] Re: LVDS to TTL converter
- From: Steven Kan <steven@xxxxxxxxxxxxxxxxxxxx>
- To: Richard Jungert <r_jungert@xxxxxxxxxxx>
- Date: Fri, 17 Jul 2009 13:21:50 -0700
> > Date: Fri, 17 Jul 2009 11:04:35 -0700
> > From: steven@xxxxxxxxxxxxxxxxxxxx
> > To: leeritchey@xxxxxxxxxxxxx
> > CC: si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: LVDS to TTL converter
> >
> > >> From: Steven Kan <steven@xxxxxxxxxxxxxxxxxxxx>
> > >> Date: 7/17/2009 10:02:51 AM
> > >> Subject: [SI-LIST] Re: LVDS to TTL converter
> > >>
> > >>> From: prasad <hariprasad.palli@xxxxxxxxx>
> > >>> Date: Thu, 16 Jul 2009 23:42:17 +0530
> > >>> Subject: [SI-LIST] LVDS to TTL converter
> > >>>
> > >>> Hi All,
> > >>> for one of my application , i would require some kind of adapter
> which
> > > can
> > >>> convert to LVDS signal to TTL signal over a frequency range upto
> > > 675Mhz.
> > >>> can you please suggest if there is any off the shelf component
> which i
> > > can
> > >>> use?
> > >> Venkat,
> > >>
> > >> Are you looking for a chip-level solution or a box-level solution? Do
> > >> you need 675 megabit data rate or 675 MHz toggle rate?
> > >>
> > >> 675 MHz toggle rate is awfully fast for a true TTL signal. What
> type of
> > >> receiver are you driving, and/or what voltage levels do you have to
> > >> achieve at the receiver?
> > >>
> > >> At the chip level we have used both National DS90LV032ATMTC and
> > >> Fairchild FIN1032MTC with good results (quad LVDS receiver, LVTTL
> > >> outputs), but these are only rated up to 400 Mbps/200 MHz. Looking at
> > >> their websites I don't see anything faster than that.
> > >>
> > >> If you need a box-level solution, we offer this module:
> > >>
> > >>
> http://www.pulseresearchlab.com/products/logic_trans/425N_T/prl-425.htm
> > >>
> > >> It will make TTL levels (2 V/50 Ohms) up to 300 MHz toggle rate, and
> > >> will toggle with reduced amplitude into the ~500 MHz range (though
> > >> that's not guaranteed).
> > >> --
> > >> Steven Kan (p) 310-515-5330 x24
> > >>
> > > Lee Ritchey wrote:
> > > Steven,
> > >
> > > I'm curious why you need to interface to TTL. There haven't been any
> > > TTL parts for some years now. Actually, I've got a few in my junk
> > > box, but I don't think that any are being manufactured now.
> > >
> > > Lee Ritchey
> >
> > Lee,
> >
> > Actually, I was responding to Venkat's request for LVDS<-->TTL
> > conversion. We make the translator box.
> >
> > We actually sell quite a lot of these. None of these are for new,
> > cutting-edge designs, but there is a lot of legacy equipment out there.
> > Some people use these for measurement and monitoring, and others use
> > them for systems integration.
> >
> > You'd be surprised at much old, slow stuff is still in widespread use.
> > We do a ton of translation to/from RS-422, because a lot of telemetry,
> > avionics, and satellite equipment uses it. People use our boxes either
> > to convert their RS-422 to LVDS and xECL for compatibility their newer
> > equipment, or they convert to TTL for use with their single-ended
> > scopes, counters, logic analyzers, etc.
> >
> > But yes, I certainly wouldn't design TTL into anything new that has to
> > run at 675 MHz.
>
> Richard Jungert wrote:
> Steven.
>
> Can you take the LVDS signal and run it thru a frequency divider
> circuit to get it down to a manageable frequency? Try to divide the
> LVDS signal frequency by say 4, 8 or 16 first then convert to TTL. I
> know it makes the TTL signal processing much more challenging but in
> this case you may not have any other choice.
>
> Richard Jungert
We could do this*, but it all depends on Venkat's application. If his
signal is a clock, then division might work. If it's a data stream or
some other pulse train, then division obviously is inappropriate.
Another approach would be to use something other than TTL. If, for
example, he's trying to drive input of an FPGA, some/many of these can
be configured for LVPECL input, which would run at those speeds. Of
course if it has a programmable input it might support LVDS directly,
too, which would solve his problem right there, with no additional
equipment.
I suppose we'll have to wait for the OP to describe his application more
fully.
* we could get from LVDS to some f/n in TTL, but not in one box. We'd
have to chain 2 boxes together (e.g. translate to ECL, then feed into
our ECL divider that has both ECL and TTL output).
--
Steven Kan (p) 310-515-5330 x24
Pulse Research Lab (f) 310-515-0068
1234 Francisco St., Torrance, CA 90502 (c) 818-620-3062
mailto:steven@xxxxxxxxxxxxxxxxxxxx
http://www.pulseresearchlab.com
Signal Buffering & Translation for Digital Design, Integration & Test
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