SN75LVCP600: Duplicate SATA redriver in signal path

Hi Lee,

Thanks for the response.

It is not our intention to add two of them but we are facing this scenario where two cards with re-drivers are already designed and this scenario of dual series drivers is coming into play. We are tying to see if we want to respin the design to have one redriver in the signal path or if the two will work as well and hence leave the design as is.

Any downside you think that will show up in this scenario?

There is the potential for some distortion of the OOB signal timing.  If this falls outside the timing window the SATA drive configuration will fail.

Regards,

Lee  

OK. Thanks for clarification. We will proceed with single re-driver in that case. 

In this same application we have insertion loss of about 15.36db due to two SATA cables/connector and additional PCB trace length in signal path.. The re-driver SN75LVCP600 compensates for up to 14db loss per the spec. The SATA 3.0 spec call for max 6db cable/connector loss. So does that mean we can do 15.36-14=1.36db < 6db and consider that re-driver will help up keep the loss within SATA spec, or does it mean re-driver will not be able to help as loss is more than 14db to begin with?

Thanks Lee.

Based on above answers, attached are two cases we came up with as a final solution. Do you see any issue here in terms of re-driver not sitting next to RX in this case. It is more like in the middle. The DEVICE and HOST blocks are given to us and we cannot change but other boards we can change.

SATA Redriver Circuit.pdf

The locations and equalization settings seem okay in the diagram.  You will likely find better eye openings at the Host by applying some DE to the signal as well.

Regards,

Lee

Hi Lee,

We did bench setup and  tested the following scenario with redrivers as shown below. This scenario provides us with SATA II link only. Playing with all the DE EQ options does not change the results.

Case 1: Adding redriver on TX on right side paddle board yields SATA III speeds keeping rest of the setup same as below.

Case 2: Adding redriver on left side paddle board on TX side yields SATA III speeds keeping the rest of the setup same as below.

Case 3 : Adding redrivers on TX on both left and right paddle boards yields SATA III speeds.

We have discussed having duplicate re-drivers are not recommended but in our test scenario the error is going the other way. Any thoughts if we should or not stick with the working scenarios in our application above.

Thanks

We need to proceed with design and hoping if Lee or any of the TI folks can comment on the last response as soon as possible. It will be greatly appreciated.

Thx

Given your lab results I would add the option for the cascaded redrivers to get SATA III operation.

Regards,

Lee

OK. Thanks. We will proceed with it.