DS90UA101-Q1: SerDes with CAT6 twisted pair as medium

Hello Even,

Can you please check what the cable insertion and return loss specifications are for the CAT6 cable you are intending to use at the desired application length? Typical applications for DS90UA101-Q1 are using automotive STP or coax cable assemblies so we do not have detailed analysis on the cable parameters for CAT6 cable to compare. 

Best Regards,

Casey 

Hello Evan,

Do you have any update on the above topic?

Best Regards,

Casey 

Casey,

I am working to get that information from cable vendor. In the meantime, can you give me a ballpark figure for acceptable insertion/return loss specifications are that will ensure decent margins, given a 917MHz line rate and 10m max cable length?

Thanks,

Evan

Casey,

Please see spec sheet for a 4 STP cable that we're looking at (using two pairs for two SerDes links, the remaining two pairs for DC+ and DC- to the remote boards):

https://www.macartney.com/media/7597/data-cable-4-stp-type-4588.pdf

Electrical characteristics

Operating voltage: 600 V
Test voltage: 4,000 V DC for 1 min (cond. - cond.)
3,000 V DC for 1 min (cond. - shield)
500 V DC for 1 min (shield - shield)
Conductor resistance: ≤ 20.0 Ω/km
Insulation resistance: ≥ 100 MΩ×100 m (shield - shield)
Capacitance: 100 pF/m
Inductance: 240 μH/Km
Impedance: 54 ±5 Ω at 1-10 MHz
Attenuation: 5.5 dB/100 m at 1 MHz
14.0 dB/100 m at 10 MHz

Thanks!

Hello Evan,

To make a determination we would need to understand the cable loss characteristic at the fundamental frequency of the forward channel signaling which is 458.752MHz in your case (38.768*28)/2. In the above spec the loss is only specified at frequency of 10MHz which doesn't give much visibility into the characteristic at the operating point for DS90UA101-Q1. Would it be possible to contact the cable vendor for more detailed information in the higher frequency range?

Best Regards,

Casey 

Hello Evan,

Any feedback here?

Thanks,

Casey 

Casey,

I just now got a response from a different vendor's cable:

Nominal loss on the #24UTP @ 458.752MHz = 15dB/100 FT (50dB/100m)

Will this be suitable for use as described above?

Thanks,
Evan

Hello Evan,

So it seems for 10m cable the insertion loss should only be about 5dB @ 458MHz. I think it is likely that this could be supported by DS90UA101-Q1. It would also be good to check the return loss specification from DC to 458MHz. 

Unfortunately we do not have test data with this type of cable, but based on the IL spec I think it is feasible. 

Best Regards,

Casey 

Casey,

From the cable mfg:

Return Loss is primarily influenced by the termination, which is beyond our control.

However, our UTP components comply with TIA/EIA-568B when properly terminated.

Thanks,
Evan