TSB81BA3E optical implementation question

Mitchell Kary

Other Parts Discussed in Thread: TSB81BA3E

Hi,

After solving my common mode problem between two PHY's on isolated grounds, I am on to my next question as I finish my 1394 optical repeater design.

I am pretty much following the guidance in the TI application note sgza001a but I have a question related to the turn on time of the optical TX following de-assertion of the TX-DISABLE. All optical transceivers I am considering specify a maximum of 1ms between removing tx disable and 90% optical power. I have measured actual times of between 20uS and 200uS in practice for various transceivers. This has the effect of reducing the toning intervals from 667uS to a duration of 467uS or so in the case of a 200uS delay. If a transceiver truly has a 1ms delay, there would be no toning period transmitted.

The question is: What is the minimum duration of a toning burst that is considered valid by the TSB81Ba3e phy? Any practical insight into this issue would be appreciated.

Thanks,

Mitch

over 12 years ago

0 Elias Villegas M. over 12 years ago

TI__Guru* 76130 points

Hello,

The minimum burst is 400us.

Another option is to create a power-up reset delay for the PHY using a RC passive circuit connected to RESET#.

Regards.

0 Mitchell Kary over 12 years ago in reply to Elias Villegas M.

Intellectual 630 points

Elias,

My optical repeater PCB is working well and I have used it to establish S800 connections reliably. However, not to belabor your last reply, but for my piece of mind, I was wondering where you got the minimum toning burst duration of 400uS. The 1394B specification I just recently obtained shows it as 667us with no minimum I could see. Is the number you provided empirical or in another specification update?

Thanks for all the help.

-Mitch

0 Elias Villegas M. over 12 years ago in reply to Mitchell Kary

TI__Guru* 76130 points

Bench test data.

Regards.

Interface

Interface forum

TSB81BA3E optical implementation question