ONET1151L Input Configuration and Bias Voltage questions

Here are the CML parameters from the customer's ASIC:

ONET1151L Input Configuration and Bias Voltage questions_CML output from ASIC.docx

Please let me know if you have any additional questions for the customer.

Thanks for your help with this!

Richard Elmquist

Has anyone had a chance to look at the request above?

Can you give a time frame as to when you might be able to provide the information?

Thanks for your help with this!

Richard Elmquist

Hi Richard,

It appears from the description and the Bias requirements that the customer is looking for a VCSEL driver. The ONET1151L is mainly targeted as an external modulator Laser driver. We have other parts that are specifically targeted for VCSELs that the customer should consider instead: ONET8501V, ONET1191V.

Now, all these Laser drivers take Analog-IN signals while giving out CML-OUT at the modulation outputs. The block diagram showing the 8501V Input-to-Output is in the 2nd page of the attached Datasheet.

Hope it helps.

Thanks,

Srionet8501v.pdf

Sriharsha,

Thanks for your response!

I will let you know if the customer has any further questions.

Richard Elmquist

Sriharsha,

The customer has further clarified their question as follows:

I am not looking for VCSEL driver. I would like to use ONET1151L as laser driver. I want to make sure that the input of ONET1151L is CML-compatible. I need this confirmation from TI.

Is the input to the ONET1151L CML compatible?

Thanks for your help with this!

Richard Elmquist

Hi Richard,

The ONET1151L has CML Outputs but not inputs. It takes in Analog Inputs only.

Most of our laser drivers have Analog IN and CML OUT.

Thanks,

Sri

Sri,

The customer has come back with the following comments:

However the answer is very confused.

Please see attached TI schematic of the evolution board of ONET1151L. As you can see, the data input, TDP and TDN, directly from PIN18/PIN19 of SFP+ Edge Connector (which is DIFFERENTIAL NETS defined by TI).

ONET1151P_L 10G SFP+ REFERENCE DESIGN_tidr437.pdf

According to Table 3 SFP+ Module and Host Electrical contact definition of SFF-8431 (SFP+ 10 Gb/s and Low Speed Electrical Interface), PIN18/PIN19 (TD+/TD-) MUST be CML logical. Please see attached SFF-8431. 

SFF-8431 Rev 4.1 + Addendum.pdf

So I think that something is not clear in datasheet. Either the datasheet needs to update or the EVM board design is wrong. Can you advise?

It looks as though the ONET1151L does have CML inputs or is the customer incorrect?

Please let me know if the customer can use the ONET1151L in his application.

Thanks for your help with this!

Richard Elmquist

Hi Richard,

I have just confirmed with the Design team- the "Analog input" for the TxD+/TxD- pins works with both CML- and VML- and ECL signal types. So you can interface the CML-signal to the input of ONET1141L as shown in the Reference design.

Both the Datasheet and the Ref design are correct. Just that it is not exclusively specified that it works with each signal type, which was the source for the confusion-sorry for that.

Hope it is clear now.

Thanks,

Sri 

Sri,

Thanks for your help!

I really appreciate your clarification.

I will let you know if the customer has any further questions.

Thanks again.

Richard Elmquist