On Nov 11, 7:29=A0pm, Gabor <ga...@alacron.com> wrote:
> On Nov 11, 12:45=A0pm, Guru <ales.gor...@gmail.com> wrote:
>
>
>
> > On Nov 11, 6:27=A0pm, Guru <ales.gor...@gmail.com> wrote:
>
> > > Hello everybody,
>
> > > I am developing a camera with a Spartan3A DSP and a sensor which uses
> > > 1.8V LVDS. The Spartan 3A DSP datasheet says that only 2.5 and 3.3V
> > > LVDS is supported. The signal rate is 108MHz DDR.
>
> > > Any suggestions what should I do? Specify in UCF LVDS_25 and pray to
> > > work OK?
> > > It is pretty much the same with a Spartan6.
>
> > > Best regards,
>
> > > Ales
>
> > I forgot to mention that transmitter (sensor) swing is typically 150mV
> > (100-200mV) and need 100ohm termination. For termination I planned to
> > use 110ohm IOB termination.
>
> > Best reagards,
>
> > Ales
>
> LVDS is LVDS regardless of the supply voltage. =A01.8V, 2.5V and
> 3.3V LVDS all have the same common-mode voltage and differential
> swing. =A0There should be mo problem interfacing these signals
> to the Spartan 3A. =A0If the Spartan 3A doesn't have integrated
> differential termination I would suggest using an external
> resistor rather than burning up internal thevenin termination
> current.
>
> Regards,
> Gabor

As far as i know It has internal differential termination.

Ales

On 11 Nov., 19:29, Gabor <ga...@alacron.com> wrote:
> On Nov 11, 12:45=A0pm, Guru <ales.gor...@gmail.com> wrote:
>
>
>
> > On Nov 11, 6:27=A0pm, Guru <ales.gor...@gmail.com> wrote:
>
> > > Hello everybody,
>
> > > I am developing a camera with a Spartan3A DSP and a sensor which uses
> > > 1.8V LVDS. The Spartan 3A DSP datasheet says that only 2.5 and 3.3V
> > > LVDS is supported. The signal rate is 108MHz DDR.
>
> > > Any suggestions what should I do? Specify in UCF LVDS_25 and pray to
> > > work OK?
> > > It is pretty much the same with a Spartan6.
>
> > > Best regards,
>
> > > Ales
>
> > I forgot to mention that transmitter (sensor) swing is typically 150mV
> > (100-200mV) and need 100ohm termination. For termination I planned to
> > use 110ohm IOB termination.
>
> > Best reagards,
>
> > Ales
>
> LVDS is LVDS regardless of the supply voltage. =A01.8V, 2.5V and
> 3.3V LVDS all have the same common-mode voltage and differential
> swing. =A0There should be mo problem interfacing these signals
> to the Spartan 3A. =A0If the Spartan 3A doesn't have integrated
> differential termination I would suggest using an external
> resistor rather than burning up internal thevenin termination
> current.
>
> Regards,
> Gabor

yep LVDS is LVDS, I guess the reason 1.8 isn't an option is
that if the transmitter is at the upper limits of spec for offset and
swing, a reciever running on 1.8V would get very close to the Vcc rail
and the spec allows voltages up to 2.4V

-Lasse

On Nov 11, 12:45=A0pm, Guru <ales.gor...@gmail.com> wrote:
> On Nov 11, 6:27=A0pm, Guru <ales.gor...@gmail.com> wrote:
>
> > Hello everybody,
>
> > I am developing a camera with a Spartan3A DSP and a sensor which uses
> > 1.8V LVDS. The Spartan 3A DSP datasheet says that only 2.5 and 3.3V
> > LVDS is supported. The signal rate is 108MHz DDR.
>
> > Any suggestions what should I do? Specify in UCF LVDS_25 and pray to
> > work OK?
> > It is pretty much the same with a Spartan6.
>
> > Best regards,
>
> > Ales
>
> I forgot to mention that transmitter (sensor) swing is typically 150mV
> (100-200mV) and need 100ohm termination. For termination I planned to
> use 110ohm IOB termination.
>
> Best reagards,
>
> Ales

LVDS is LVDS regardless of the supply voltage.  1.8V, 2.5V and
3.3V LVDS all have the same common-mode voltage and differential
swing.  There should be mo problem interfacing these signals
to the Spartan 3A.  If the Spartan 3A doesn't have integrated
differential termination I would suggest using an external
resistor rather than burning up internal thevenin termination
current.

Regards,
Gabor

On Nov 11, 6:27=A0pm, Guru <ales.gor...@gmail.com> wrote:
> Hello everybody,
>
> I am developing a camera with a Spartan3A DSP and a sensor which uses
> 1.8V LVDS. The Spartan 3A DSP datasheet says that only 2.5 and 3.3V
> LVDS is supported. The signal rate is 108MHz DDR.
>
> Any suggestions what should I do? Specify in UCF LVDS_25 and pray to
> work OK?
> It is pretty much the same with a Spartan6.
>
> Best regards,
>
> Ales

I forgot to mention that transmitter (sensor) swing is typically 150mV
(100-200mV) and need 100ohm termination. For termination I planned to
use 110ohm IOB termination.

Best reagards,

Ales

Hello everybody,

I am developing a camera with a Spartan3A DSP and a sensor which uses
1.8V LVDS. The Spartan 3A DSP datasheet says that only 2.5 and 3.3V
LVDS is supported. The signal rate is 108MHz DDR.

Any suggestions what should I do? Specify in UCF LVDS_25 and pray to
work OK?
It is pretty much the same with a Spartan6.

Best regards,

Ales