[SI-LIST] Re: LVDS to TTL converter

Steven.

You may have to take the data stream and first extract the clock signal with a 
different circuit. Then take the extracted clock in LVDS divide it down to a 
manageable TTL frequency. In this world of engineering it takes hard work and 
creativity to get exactly what you want. Not always is there an easy solution. 

Richard Jungert



> Date: Fri, 17 Jul 2009 13:21:50 -0700
> From: steven@xxxxxxxxxxxxxxxxxxxx
> To: r_jungert@xxxxxxxxxxx
> CC: si-list@xxxxxxxxxxxxx; leeritchey@xxxxxxxxxxxxx; 
> hariprasad.palli@xxxxxxxxx
> Subject: Re: [SI-LIST] Re: LVDS to TTL converter
> 
> >  > 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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