Forums

1.8V LVDS on spartan3A DSP

Started by Guru November 11, 2009
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
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
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 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, 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