TUSB214: actual layout check and path loss

Hi Lisa,

Lisa Xu said:

1. This layout is suitable or not?

These are two redrivers on one PCB with a total length of 36 inches, correct? If so, I believe it may not be necessary to use two redrivers, one may be sufficient. However, if you want to be safe, you can still use both redrivers and start them at a lower boost level (level 0 or 1). My main concern is that our redrivers typically can support up to 5 meters, and by implementing two into system with a length of roughly 1 meter, it may end up over-compensating and causing false-disconnects in the system.

Lisa Xu said:

2. if not suitable, how to change?(T1 Should <16inch)

We recommend placing our redrivers closer to the connector, so my recommendations would be as follows:

If using two redrivers, place one near the SOC and one near the connector at lower boost levels.

If using one redriver, place this redriver closer to the connector at boost level one or two.

Lisa Xu said:

3. If just USB Signal Conditioner(TUSB214) is not suitable for this design, Could you introduce other TI product?

A USB2 redriver should be sufficient for HS signal compensation. In this case, I would recommend one of our newer redrivers, the TUSB211A, TUSB216, or the TUSB217A, as these come with our newest features in RX Sensitivity, and have general improvements over older versions such as the TUSB214.

Please let me know if you have any other questions.

Thanks,

Ryan

Hi Ryan:

Thanks for your kindly explanation.

Your concern: My main concern is that our redrivers typically can support up to 5 meters, and by implementing two into system with a length of roughly 1 meter, it may end up over-compensating and causing false-disconnects in the system.

==》I checked from TUSB214 datasheet,the 5m mentions for cable length,but on PCB it is Stripline.And I got from some document it seems signal get more path loss/insertion loss on Stripline than USB cable, Maybe my information is wrong, Pls help correct if wrong.Thanks

So

1. How to avoid the <over-compensating and causing false-disconnects in the system> which you concerned, just delete the TUSB214 near SOC or other method? 

2. TUSB214 just has Signal Conditioner for USB2.0 high speed, and no any activity for USB low speed and full speed, so generally it seems there is no need to compensate for the low speed and full speed signal,right?

3. From aspect of signal attenuation(insertion loss), could you share when will we need add one signal conditioner(TUSB214)? when will we need add two?(Generally or per your experience),and could you also share some document to state this topic if possible? 

Thanks

Best Regars

Lisa

Hi Lisa,

Lisa Xu said:

==》I checked from TUSB214 datasheet,the 5m mentions for cable length,but on PCB it is Stripline.And I got from some document it seems signal get more path loss/insertion loss on Stripline than USB cable, Maybe my information is wrong, Pls help correct if wrong.Thanks

This can be dependent on the cable used, PCB material, cable wire thickness, and the general construction of the wire. It is not necessarily more loss.

Lisa Xu said:

1. How to avoid the <over-compensating and causing false-disconnects in the system> which you concerned, just delete the TUSB214 near SOC or other method? 

If you want to maintain using two redrivers, you can set them both to a lower boost level, level 0 or 1, and if you are seeing the signal disconnect due to over compensation, you can remove the TUSB214 at the SOC like you recommended, or adjust the resistor value used for the EQ pin.

Or, you can just use the redriver closer to the connector, and set it at a higher level, and see if that meets your needs.

Lisa Xu said:

2. TUSB214 just has Signal Conditioner for USB2.0 high speed, and no any activity for USB low speed and full speed, so generally it seems there is no need to compensate for the low speed and full speed signal,right?

Our redrivers cannot compensate for LS/FS, correct. And if LS/FS is not being used, then yes, I believe there is no need to compensate, not that we are able to.

Lisa Xu said:

3. From aspect of signal attenuation(insertion loss), could you share when will we need add one signal conditioner(TUSB214)? when will we need add two?(Generally or per your experience),and could you also share some document to state this topic if possible? 

Generally, we recommend using two redrivers in any system that is greater than 5 meters in length. If the system is within 5 meters, then generally we believe customers should only need one redriver, unless there is a large amount of connectors or a high-amount of loss. Your current system is roughly 3 feet/1 meter, so I do not believe two redrivers is required. Though, again, if you wish to try with two, you can, and if there is any issue, you can simply remove one of the redrivers. We do not have any documents currently which illustrate when 1 or 2 redrivers should be used outside of recommending two for distances longer than 5 meters.

Please let me know if you have any other questions.

Thanks,

Ryan