DIX4192: SPDIF cable reach

Hi Kawai-san,
In general, as far as S/PDIF audio signals go, the limitations of the cable length is a function of many factors such as -
1. Quality of sender (Tx module)
2. Sensitivity of the Receiver (RX module)
3. Loss in the cable.

Per the spec, the minimum guaranteed to work is 5m (15') with any cable. With better Tx/ Rx combinations *might* work on longer runs if using a good cable, but I would recommend an extender for anything longer than 5m for overall robustness of the system functionality. NOTE that since there are many factors in the mix, it's quite tricky to objectively quantify how much headroom you have left when you are testing w. longer length.

Hope this clarifies things. Thanks.

Best regards,
Ravi

Hi Ravi-san,

Thanks for your support and advice.

When using DIX4192 on both side of TX and RX and to achieve 20m, what would be your or  TI recommendation/solution ?

Do you or TI interface team have any idea ?

Best Regards,

Kawai

Hi Ravi-san and Team,

We need your help. What is TI solution to extend cable reach ?

Best Regards,
Kawai

Hi Kawai-san,
I have been in touch w. the interface team here in TI and will get back w. you with their feedback. Thanks.

Best regards,
Ravi

Hi Ravi-san,

I accidentally clicked the "this resolved my issue" button when I wanted to reply.

Do you have any update talking with the interface team ?

I have another question that if we use "AES3" interface instead of using S/PDIF interface, would it be possible to achieve over 20m transmission between the two DIX4192 ?

The reason is that DIX4192 output is also AES3 compliant. I do understand it would depend on cable insertion loss, however, AES3 standards say that it can go up to 100m+. Can you recommend below design for AES3 20m transmission ?

Hi Kawai-san,
As discussed earlier in this thread, there are more than one tangent for a given application to work reliably over the 20m cable length. There is no easy answer and it depends on many parameters. I would summarize the situation as below -

- For Balanced output, you can get upto 10m range for 192kHz sampling rate. With lower sampling rate, it will work on longer cable length. It will still depend on the wire quality and impedance which must be ideally 110 Ohms.

Recommended output circuit is in datasheet. For transformer, you can use pulse transformer DA102C or PE-65612 or S22083 or LL1572. We can recommend external line drivers (example of this is outlined in DS)if the overall performance w. 20m cable is lacking depending on the sampling rate for this application.

To summarize, we would need to test the overall system performance at sampling rate of choice and selected cable length and make additional choices for overall system performance. Thanks.

Best regards,
Ravi

Hi Ravi-san,

Yes, I do understand there are many parameters related.

If you would say 10m range for 192kHz sampling rate, what is the estimation of the insertion loss for this 10m cable ? If it is a cable which has -10dB with 10m characteristic, we could just choose a cable which has better performance, such as -10dB with 20m.

I agree that you could not guarantee the cable reach, however, we wanted to know if DIX4192 AEA3 compliant output has same "ABILITY" or "POSSIBILITY" to achieve over 20m cable since AES3 standard say up to 100m or 150m (Maximum, this must prepare very high quality cable).  I believe DIX4192 TX interface is similar like RS-422/485 and the data rate is only from a few Mbps to 10Mbps, which does not have much insertion loss.

With my understanding, LVDS, RS-422 or RS-485 interface could drive more than 50m at 50Mbps using CAT5e cable (could be more than 100m for RS-422/485). So, I though 20m may not be a high hurdle.

We will ask customer for evaluation in his system, however, at least we need to prepare a solution which could possibly achieve their requirement.

Best Regards,
Kawai

Please allow me to intervene into this Q&A session.
First of all, can you give me the answers to the questions bellows.

Item 1. Please let me know if the driver in DIX4192 is electrically compliant to AES3 physical
layer specifications, if it is used with circuit in the Figure 77. Transformer-Coupled
Balanced Output Interface.
(Required Amplitude should be: 2.0 V < Vo diff < 7.0V vs. 5.4 V min)

Item 2. Please let me know if the receiver in DIX4192 is electrically compliant to AES3 physical
layer specifications, if it is used with circuit in the Figure 72. Transformer-Coupled Balanced
Input Interface
(Required Amplitude should be: 0.2 V < Vo diff vs. 200 mV max)

I understand that the amplitude is one of the AES3 parameters. There may be another factors.
If DIX4192 does not meet nay of the factors, please let me know.

If the answers are Yes, AES document stated bellows:
I think that 20 m cable reach is feasible, as long as, the I/O of DIX4192 is electrically
compliant to those of AES3
What do you think of it?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Chapter 3
THE PHYSICAL (ELECTRICAL) LAYER

3.2. Guidelines for installation
The following practical guidelines have been produced for balanced circuits intended for the
AES/EBU Digital Audio interface. They are based on experience gained from two installations
by the BBC in London and from installations by CBC, Canada

Inter Area Cabling

- Cables should have a characteristic impedance of about 110 W (80-150 W is acceptable).

- Multicore twisted pair cables with an overall screen are best for installations where
runs do not exceed 150 m. (Overall double screens give better EMC protection.)

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Mita