SN75LVCP422

Hello Jacek Kupinski

Yes, you can do it. Just you will need to be careful with the pre-emphasis selection.


Best regards
Francisco Zamudio

Thanks, need clarification on that note. Reading the datasheet my impression is the D0, D1 and EN are already preselected at the chip level by tying the to VCC [111] page 4 TERMINAL FUNCTIONS:
(1) D0 and D1 are tied to VCC via an internal PU resistor.
(2) EN tied to VCC via an internal PU resistor.
is my understanding correct?

Thanks,
Jacek

No, is not (you can see the true table on page 3). With this configuration you will have 2.5 dB pre-emphasis, this comment is about the internal PU resistors (you can see the Figure 1). But if you want to change the pre-emphasis level, you can change the values of these terminals.

Best regards
Francisco Zamudio

And one another question:
product spec defines the suggested cable length for the case when the repeater's receiver is a HD controller to be 2m. If I want to extend this length and put say another repeater at the end of that cable what would be the typical and maximum length of the cable the second repeater it would still recognize the eye?

Thanks,
Jacek

Yes, You can use 2 m in the second cable. I recommend in the first redriver use the default configuration and in the second redriver, you can use a 2.5 dB pre-emphasis.

Best regards
Francisco Zamudio

The SAS cable I use for this configuration causes P output from first redriver to be connected to N input of the second redriver [ and opposite to the negative path] - is altering the phase of the SATA signal acceptable or it would cause not correct functionality?

Hello Jacek

This redriver is SATA redriver, then, I recommend to use a SATA cable. I also recommend to connect the P output from the first redriver to P input of the second redriver.

Best regards
Francisco Zamudio

Hello Jacek

Do you have a problem with your connection? Your question were answered?

Best regards

Francisco Zamudio

Yes my questions were answered although I still have the problem we use this IC as a SATA to SAS interface and then drive ~4m SAS cable then we have another SAS to SATA redriver. I believe we change phase of the bit by driving TXP[1] to RXN[2] and so on. We need to figure that out.

I wanted to clarify the pin description for the IC:

3. RX_0P - Input 0, non-inverting                     OK

4. RX_0N Input 0, inverting                               OK

7, TX_1P Output 1, inverting                             why?

8. TX_1N Output 1, non-inverting                    why?

13. RX_1N Input 1, non-inverting                    why?

14. RX_1P Input 1, inverting                             why?

17. TX_0N Output 0, inverting                           OK

18. TX_0P Output 0, non-inverting                   OK

We are confused by the fact of mixing phase of the transmitting bits. Can you comment? One side of the chip is connected to a SATA cable the other side goes to SAS connector and the SAS cable connects it to identical device [cascade configuration] and the same site receives the signal using another SATA cable. 

Fundamentally I don't see any wrong doing although it doesn't work. The cable length is rather short less than 1m].

Thanks,

Jacek

Hello Jacek

I think you won't have any problem with the phase if you have a correct connection in the RX and TX (channel 1). Currently I'll check the correct description of the table with the right people. If you can, please try to connect this channel with the same configuration of the channel 0 and send me your feedback. If is possible, please send me a block diagram of your complete connection. You need to remember this device is a SATA redriver.

Best regards
Francisco Zamudio

Thank you for your help. I have sketched the configuration of what we intend to use. Can you provide me with email address so that I could include the *.pdf file?

Thanks,

Jacek