We have a fairly significant failure rate of these devices. I am looking for some ideas on why?
The chips are used in down-hole systems. Oil drilling equipment is subject to very harsh environment. The equipment is subject to rough handling, sees very high vibration and sometimes shock, as well as temperature extremes. Some places, the equipment might start the day at -20C and then go to 120C during operation. Other places, the temperature might rise to 170C. On the flip-side, we have seen failures to a lesser degree during production before the equipment goes to the field.
Most of the circuit boards have protection against accidentally applying 36V across the A/B lines. The chip itself is supposed to be ESD protected.
The most typical failure/symptom is the RX stops working.
So I have some questions, and maybe you have additional questions/ideas:
- Does this chip require power sequencing? For example, can the A/B lines be active without the chip powered up?
- Any chance to cause a latchup problem?
- How important are series resistors on the A/B lines? We don't have any.
- Should additional electrically fast transient protection be applied to A/B lines?
- How sensitive are these parts to high vibration?
- Is it possible that we are inducing infant mortality during production? For example, improper handling?
- Our production model screens all boards in HASS. They are exposed to cycling temperature and vibration. Does this remove life from this part?
In addition to these, can you make any other comments/recommendations?