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SN75LVPE802: Regarding to the function and layout

Masakazu Adachi
Intellectual 2500 points
Part Number: SN75LVPE802

Hello team,

I received questions from the customer.

1. Sorry for the rudimentary question, but could you please tell me the role of the equalizer in a SATA re-driver?

2. The customer did not understand the meaning of the wiring lengths in Figure 2 of the datasheet. What does 16-in,4-mil + 2-in,9.5-mil mean?

3. In 9.2.4.1 of the datasheet there is a waveform for TP4, is the Trace Length the length of TP3 to TP4?

4. 9.3.1 describes AC coupling capacitors, is a capacitor required before the input/output pins of the re-driver even if it is used only with SATA?

5. Is it correct to recognize that the De-emphasis and Equalization settings should be checked while debugging?

6. Will the re-driver be less effective if the SATA SW is passed through in the middle? Is it necessary to take this into consideration when placing the device?

7. Regarding the SATA TX signal n with the chipset as HOST, which is the customer's specification, the following four patterns are assumed.

Pattern 1 is to connect to the SATA connector at 242mm via SATA SW twice.
Pattern 2 connects to the RAID IC at 223mm via SATA SW once.
Pattern 3 connects to the RAID IC at 225mm via SATA SW once.
Pattern 4 connects to the SATA connector at 338mm via SATA SW twice.
7-1. Is it appropriate to place it right after the PCIe connector?
7-2. Pattern 4 will have a very long route (338mm), will using two re-drivers be effective? Also, are there any adverse effects of using multiple re-drivers?

8. Will the effect of the re-driver be reduced if the SATA SW is passed along the way? If so, is it necessary to take this into consideration when placing the re-driver?

Please let me know if you need any additional information so that I can check with the customer.

Regards,

Masa

  • 0
    TI__Genius 14781 points

    1.. The input equalizer is designed to recover a signal even when no eye is present at the receiver. 

    2. 16 inches is the length and width of trace is 4 mil. Second case is a 4-inch-long trace that is 9.5 mil in width. Third case is an 8-inch-long trace that is 4 mil in width. 

    3. Different trace lengths are used. The output eye figures (TP4) on the right-hand side show the input trace length which is the length of the trace between TP3 & TP4. 

    4. Yes, device still requires AC coupling caps. 

    5. Please describe what is being debugged? 

    6. Typically for most of our redrivers, we recommend they get placed in the middle so gain can be same on Rx and Tx side. Our EVMs are designed this way. 

    7.1 Placement depends on application and environment. I don't see any potential issues by placing redriver immediately after the connector. Many customers do this without any issues. 

    7.2. The device is able to compensate up to 40 inches of FR4 material at 8 Gbps and up to 50 inches of FR4 trace at data rates of 3 Gbps lower. If your loss is over any of these two scenarios, a second redriver should be considered. 

    8. Can you please elaborate on this? I am not sure what you're referring to when you say "along the way?" 

    Regards, 

    Vicente 

  • 0 in reply to vicente flores prado
    TI__Intellectual 2500 points

    Hello Vicente,

    I received feedback from the customer. Please confirm following,

    vicente flores prado said:
    5. Please describe what is being debugged?

    Debug means SATA compliance. Is it OK to recognize that you can adjust settings while reviewing the compliance waveforms? Compliance will be implemented in the future. 

    vicente flores prado said:
    6. Typically for most of our redrivers, we recommend they get placed in the middle so gain can be same on Rx and Tx side. Our EVMs are designed this way. 

    Does "get placed in the middle" mean placing the redriver in the middle of Host and Device?
    When deployed like Host - Redriver - HD3SS3212RKSR - HD3SS3212RKSR - Device, can the Redriver assume how many inches of trace length will be attenuated by the HD3SS3212RKSR?

    vicente flores prado said:
    8. Can you please elaborate on this? I am not sure what you're referring to when you say "along the way?"

    The same question as No.6, so only the No.6 answer is OK. 

    And additional question,

    9. If a through-hole or stub is present in the trace, will the redrive wire be shorter? What, if any, is specified, for example, the number of through holes? 

    Regards,

    Masa

  • +1 in reply to Masakazu Adachi
    TI__Genius 14781 points

    Hi Masakazu, 
    No. Typically if you leave settings as is. If you fail compliance testing you adjust the EQ settings and restart testing. 

    The redriver is not aware of insertion loss due to trace length. Customers need to have an educated guess about the insertion loss the redriver needs to compensate for.

    Vias are typically not recommended under high speed traces. If use of vias is unavoidable, ensure backdrilling to reduce stub length. 

    Regards, 

    Vicente 

  • 0 in reply to vicente flores prado
    TI__Intellectual 2500 points

    Hello Vicente,

    Thanks for the support. I shared it with the customer.

    Regards,

    Masa