Hi Chris.
Can you share what are the symptoms of your non-working boards ?
Have you confirmed that the voltages on the non-working boards are compliant to the recommended specs ?
Could the fault be some other issue ? Can you share partial schematics and/or PCB layout details ?
Does your device simply plug into a standard PC ? How were these protos tested ? They failed how and when during your testing ? If you replace the BGA XMOS device, the board works again ?
What is your capacitive load on VBUS ?
The ESD device you are using is from ST and openly have a hard time in believing that ST would build in high volumes and ship the referenced component that does not meet the posted specs. You most certainly have many options for ESD protection and also EMI filtering. We can share some vendor details if there is an interest. Our company is about to roll out a list of widgets based on USB 2.0 Full Speed, High Speed and also USB 3.1 Super Speed. For each, we are using different ESD protection devices. In addition, we have a polymer fuse in line with VBUS. To remain competitive, we source these devices direct from the manufacturers in China. You should be able to do the same with even single T&R qty.
Check your power supply rails since this XMOS device contains an internal switching power supply. Many moons ago, we beta tested the Oxford (UK) PCI Express UART line before they went into production and we raised a similar power supply observation in that their power supply did not fire up every time. The comment was not taken as a serious concern. Fast forward about 8 years later and PLX Semiconductor (they bought Oxford Semiconductor) raised an errata note on exactly the same fault we noted at the start of the review. Their work around for the Oxford device was to use an external power supply for the 1v2 rail :(
If you suspect the ST ESD part to be not suitable then you should be able to ping your local FAE at ST and raise the case. They should then request to see the parts on the non-working board for a root cause analysis. If you are using a contract manufacturer, they may (should) have an X-RAY inspection system which would allow to review the insides of a 'good' XMOS device to compare against a 'defective' XMOS device. Will be really interesting to see where the issue lies for your boards. Please proceed till you find a suitable answer else you will have the wrath of RMAs.
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We are using the following device in our pending projects for USB 2.0 & USB 3.1 Gen 1 (USB 3.0):
http://www.socay.com/upfile/201407020248027678.pdf
Notes:
1) the Vbr value is 6 volts as compared to the TI part noted by Caleb @ 11v. Lower is better here.
2) Capacitance is 0.3 pf as compared to the TI part @ 1.5 pf. This part is suitable for USB 2.0 HS (480 Mbps) and also USB 3.1 Gen 1 (aka USB 3.0) 5 Gbps. Lower capacitance is better.
3) Socay part is IEC61000-4-2 (ESD); IEC61000-4-4 (EFT); IEC61000-4-5 (Lightning) compliant vs. TI part being IEC61000-4-2 (ESD) only. More the better.
Socay is a true manufacturer of the parts and they often supply the many brand names seen in the catalog shops like Digikey and Mouser. We have met with this manufacturer in HK at past trade shows and their products match the specs they advertise. We have verified this against their line of polymer fuses and where others failed during our testing, Socay met all of our requirements. They are certified against the required specs including UL, CE, CSA, etc.
They are flexible on qty and the parts are very low cost as compared to their landed branded versions.
For example:
Part Number: ULC0524P
Quantity: 3 K
Unit Price: 0.042 USD/ pc
Same as Littlefuse SP3010 device:
http://www.littelfuse.com/~/media/elect ... et.pdf.pdf
Contact details:
Cindy
socay012@socay.com <
socay012@socay.com>
We also encourage you to place an in-line polymer fuse on the Vbus line to limit excessive currents. Socay also offers these devices in assorted current / trip values. Hope this helps.
Kumar