DS90LV804: maximum cable length

Sato-san

Is the receiver Type-1 or Type-2 receiver? Please take a look at this app note: http://www.ti.com/lit/an/slaa844/slaa844.pdf.

Thanks

David

Hello David-san,

Type-1 or Type-2 means you would like to confirm whether the receiver input needs offset on LVDS signal or not?

Best regards,

Sato-san

The TIA/EIA-899 standard describes two types of receivers, Type-1 and Type-2. The Type-1 receiver has a differential input voltage threshold centered on 0 V, while the Type-2 receiver has an input threshold centered on 100 mV. This offset input voltage provides a valid bus state with no voltage difference and can be useful during bus faults or idle-line conditions. Since the signal at the input of the receiver does not change instantly, the additional time for the input to slew to the offset threshold of the Type-2 receiver is expected to induce more time jitter than a Type-1 receiver.

Since we are using jitter to determine the max cable length, the difference between Type-1 and 2 in terms of the jitter performance as stated above needs to be taken into account as well. 

Thanks

David

Hello David-san,

The receiver type is Type-1, input voltage threshold centered on 0V.

How long cable length can the device support?

and I would like to know the length in case of Type-2 receiver, if possible.

Best regards,

David-san,

Thanks for comment, I understand we can use CAT-5e cable for the estimation.

DS90LV804 is 800Mbps device and customer case is 560Mbps. However, all devices measured in the app note are 400Mbps device. Which device result in the app note can we reference for estimating the max cable length of DS90LV804 with CAT-5e cable?

And I would like to estimate 560Mbps case, so I would like to know if I can think that cable length is inversely proportional to data rate?

Do you think 10m length of CAT-5e cable can be supported with DS90LV804, 560Mbps?

Looking at results of app note, 10m length cannot achieve 560Mbps even with 20% jitter percentage. What do you think the case of DS90LV804?

Best regards,

Sato-san

Table shows 10m CAT5 can't achieve 560Mpbs even with 20% jitter. If they want to use 10m of FX15-31S-0.5SV, the attenuation of the cable must be better than the CAT-5 cable.

How much is the attenuation of FX15-31S-0.5SV at 560Mpbs? You can use use sinusoidal signal loss of 6 dB at the signaling rate in hertz as a good and conservative estimate for the maximum cable length. For example, if a cable has a 0.197dB/m loss at 100Mbps, then the max cable length at 100Mbps will be 6/0.197 = 30m.

Thanks

David

Hello David-san,

Thanks for your comments.

I understand it highly depends on FX15-31S-0.5SV and require some testing with the cable.

Do you think DS15BR401 is more certain for 10m with 560Mbps?

The signal is like output of DS90C385A, which is actually built in FPGA. Do you have any good recommendation for its buffer/repeater?

Best regards,