Hi All, So, it looks like it's OK for me to use an unterminated LVDS input on an I/O bank with Vcco = 3.3V. I even checked that the tools don't complain! Does anyone know of any data for Vicm (the common mode range) for these inputs? If the receivers are powered by Vccaux, I assume the spec is the same as for LVDS_25, otherwise maybe the spec scales with Vcco. TIA, Syms.
Virtex-4 Vicm for LVDS with Vcco = 3.3V.
Started by ●July 11, 2006
Reply by ●July 11, 20062006-07-11
Symon, The LVDS input buffer is a full CMOS differential comparator. You may go within ~ 0.6 volts of either ground, or Vccaux, and it will still meet speed spec. You may go all the way to the rails (and even a bit beyond -- see abs max pin V specs), but then you take the diff stage out of its linear region, and it gets a bit slower. Austin Symon wrote:> Hi All, > So, it looks like it's OK for me to use an unterminated LVDS input on an I/O > bank with Vcco = 3.3V. I even checked that the tools don't complain! Does > anyone know of any data for Vicm (the common mode range) for these inputs? > If the receivers are powered by Vccaux, I assume the spec is the same as for > LVDS_25, otherwise maybe the spec scales with Vcco. > TIA, Syms. > >
Reply by ●July 12, 20062006-07-12
Hi Austin, Thanks for your reply, that's cleared up my question! Cheers, Syms. "Austin Lesea" <austin@xilinx.com> wrote in message news:e90o4d$bt8@xco-news.xilinx.com...> Symon, > > The LVDS input buffer is a full CMOS differential comparator. You may > go within ~ 0.6 volts of either ground, or Vccaux, and it will still > meet speed spec. > > You may go all the way to the rails (and even a bit beyond -- see abs > max pin V specs), but then you take the diff stage out of its linear > region, and it gets a bit slower. > > Austin > > Symon wrote: >> Hi All, >> So, it looks like it's OK for me to use an unterminated LVDS input on an >> I/O >> bank with Vcco = 3.3V. I even checked that the tools don't complain! Does >> anyone know of any data for Vicm (the common mode range) for these >> inputs? >> If the receivers are powered by Vccaux, I assume the spec is the same as >> for >> LVDS_25, otherwise maybe the spec scales with Vcco. >> TIA, Syms. >> >>
