TUSB1002: functioning different for 3m cable transmission with different SSD devices

Shuai Jin

Part Number: TUSB1002

Hi,

We have the TUSB1002 EVM evaluation board to test how TUSB1002 works. We observed:

1) when it is loaded with Sumsung portable SSD it can work in USB3.0 with MODE F. I can measure the around 5Gbps 1-0 patterns in Tx/Rx after plug in the cable. But when it is in MODE 1 the HOST cannot identify the SSD.

2) when it is loaded with SanDisk portable SSD it only work in USB2.0 with MODE F. I can measure the around 50Mbps 1-0 patterns in Tx/Rx after plug in the cable. But when it is in MODE 1 the HOST cannot identify the SSD.

So my questions are:

1) Why loaded with different SSD it behaves different as USB3.0 and USB2.0 respectively.

2) How HOST identify the device in USB3.0? By sending "Handshake" package with 1-0 patterns? Are the 5Gbps and 50Mbps 1-0 patterns "Handshake" patterns? But the data rate is different.

3) How HOST identify the device in USB2.0? By continuing sending 1-0 patterns? We didn't catch any "Handshake" patterns on Channel D+/D- in measurement.

4) Will HOST with USB2.0 and USB3.0 detect the device simultaneously? Or HOST detect USB3.0 first and see if the device support USB3.0, if not it will detect for USB2.0?

Regards,

Shuai

Mastermind 32545 points

Diego Cortes
- May 19, 2017 3:17 PM
Hello Shuai,

The reason is that some devices (SanDisk SSDs included) have a compatibility issue when detecting the TUSB1002 RX terminations, we already have a workaround but it has not been updated to the reference design (the new EVM units will include this fix). the workaround is to include 265nF AC coupling capacitors between the RX terminations and the USB connector. It has been successfully tested without compromising the device´s performance.

Regards,

Diego.
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Shuai Jin
- May 25, 2017 3:50 PM
In reply to Diego Cortes:

Hi Diego,

Thanks for your reply. I illustrate the workaround as the figure below with a 265nF AC cap between EQ RX and USB connector. Is it correct? Another question is that usually the SanDisk itself has AC coupling capacitor at its own output port, so can you please show me why another 265nF AC cap is needed here?

Thanks,

Shuai
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Diego Cortes
- May 25, 2017 5:25 PM
In reply to Shuai Jin:
Hi Shuai,

This capacitor provides two positive effects: It is useful for ESD/EOS protection and removes unwanted bias level from Rx side. Because RX side of different UBS-SS system have variable common mode voltage (use different termination scheme, like the case od the SanDisk drives), this option can remove unmatched bias level for interconnection logic.

Regards,
Diego.
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Shuai Jin
- May 29, 2017 7:35 PM
In reply to Diego Cortes:

Hi Diego,

We followed your suggestion to add AC caps between RX of EQ and SanDisk SSD on the evaluation board. But it still works in USB2.0 instead of USB3.0. The device is SanDisck Extreme 900 Portable SSD. Can you plz give me more details to have the evaluation board functioning in USB3.0 with this SanDisck portable SSD?

Thanks,

Shuai
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Diego Cortes
- May 30, 2017 3:53 PM
In reply to Shuai Jin:
Hi Shuai,

Have you tried to change the EQ settings?, Perhaps the channel needs different compensation. please let me know which cables are you using and the settings for EQ and CFG for each channel.

Regards,
Diego.
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TUSB1002: functioning different for 3m cable transmission with different SSD devices