DS30BA101: DS30BA101/DS30EA101 - Balanced Differential 150 ohm

Philip Van Atta

Part Number: DS30BA101
Other Parts Discussed in Thread: DS30EA101, LMH0302, LMH0303

Hello, I would like to use the DS30BA101 and DS30EA101 to transmit and receive 8b/10b encoded data over balanced 150 ohm cable differentially. The cable is about 4 meters long with several matched connectors inline. The data sheets only show 100 ohm differential cable and 75 ohm single ended coax cable applications. Can I set it up for 150 ohm differential termination and adjust Rvo for 800 mV p-p differentially and have equalization and data transmission work properly?

Thanks - philip

over 5 years ago

0 Nasser Mohammadi over 5 years ago

TI__Guru* 88775 points

Hi Philip,
DS30EA/BA101 supports 75-ohm single ended and 150-ohm differential. As you noted, you can fine tune RVO to get desired differential amplitude. However, I believe minimum single ended VOD is about 760mV so differential would be about 1.32V. You may need to use passive attenuator to get to 800mV differential. Could you please let me know the application and data rate?

Regards,,nasser

0 Philip Van Atta over 5 years ago in reply to Nasser Mohammadi

Prodigy 75 points

Thank you for your response Nasser. The application is to carry a 1.25 Gbps 8b/10b encoded signal on 150 ohm balance STP cable previously used for Fibre Channel at 1.0625 Gbps. The only reason I would want to get the signal level down to 800mv p-p differential is because that is what is recommended by the DS30EA101 receiver data sheet. If that is necessary, can you suggest a passive attenuator network? Thanks!

0 Nasser Mohammadi over 5 years ago in reply to Philip Van Atta

TI__Guru* 88775 points

Hi Philip,
DS30EA101 800mV requirement is for single ended operation. Since you are operating in differential 150-ohm then you should be fine.
Can you please let know part number for this STP 150-Ohm cable? I normally see 100-Ohm STP.
Regards,,nasser

0 Philip Van Atta over 5 years ago in reply to Nasser Mohammadi

Prodigy 75 points

Actually, I don't know that it is STP cable. I do know that it is balanced 150 ohm. I still may want to reduce the signal level. What would be the value of Rvo for the minimum output signal level you mention above?

0 Nasser Mohammadi over 5 years ago in reply to Philip Van Atta

TI__Guru* 88775 points

Please try about 768-ohm. This will give us about 3% less VOD than suggested 750-ohm resistor. This should give us about 760mV - I had a typo in my earlier response and I noticed I had 660mV.

Regards,,nasser

0 Philip Van Atta over 5 years ago in reply to Nasser Mohammadi

Prodigy 75 points

Hi Nasser. Can you suggest an attenuation network on the transmit side?

0 Nasser Mohammadi over 5 years ago in reply to Philip Van Atta

TI__Guru* 88775 points

Hi Philip,
Please note link below. This provides different passive attenuator for either 75 or 50 ohm environment.
www.rfcafe.com/.../attenuator-calculator.htm

Regards,,nasser

0 Philip Van Atta over 5 years ago in reply to Nasser Mohammadi

Prodigy 75 points

Hi Nasser. Do you know what the additive jitter for the DS30BA101 would be? Is it similar to what is documented in the LMH0302 data sheet?

thank you - philip

0 Nasser Mohammadi over 5 years ago in reply to Philip Van Atta

TI__Guru* 88775 points

Hi Philip,

It is the same as LMH0302 additive jitter(~18ps).

Regards,,nasser

0 Philip Van Atta over 5 years ago in reply to Nasser Mohammadi

Prodigy 75 points

How can I determine the maximum additive jitter for the DS30BA101 and DS30EA101? I think we can use the 2 cases for 1.5 Gbps over RG59 and CAT6 cable for the equalizer as in the data sheet, if you have that information.

Thank you - philip.

0 Nasser Mohammadi over 5 years ago in reply to Philip Van Atta

TI__Guru* 88775 points

Hi Philip,

Please confider using typical data noted in DS30EA101 and LMH0303 data sheets and add 30% to mitigate this parameter over temperature and across different device.

Regards,,nasser

Interface

Interface forum

DS30BA101: DS30BA101/DS30EA101 - Balanced Differential 150 ohm