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Part Number: LME49724
We use the LME49724 for balanced audio line out as a single ended in to differential out. Recently we have been seeing some parts failing our tests by being out of spec. They fail the signal to noise limit that usually has a very high acceptance threshold under normal operating conditions. The noise floor has been noticeably higher on the parts that fail. After we replace the LME49724 then it tests fine. Is there anything in the circuit that could be causing this?
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In reply to Luis Fernando Rodriguez S.:
In reply to Alan Hoehn:
Is the lot code the series of characters next to the "N" symbol. The failed units I have seen are labeled 82D5 and 89J2.
How exactly do I check the analog input noise level? I did run a 1KHZ sine wave through the part and the output was slightly more noisy.
I removed the ferrite beads and TVS components with little effect as they were still out spec for SNR. Every time we replace the failed part with a new one our manufacturing SNR tests pass.
As far as the percentage number of failures. That is difficult for me to give an exact number as this has been an ongoing problem for several years and they would just replace the chip since there were so few. Probably about less than 1% although it has been over 5% since last November. Most units are passing and there are many passing ones with the 82D5 and 89J2 lot codes.
I started to notice a trend on the failing units. I an enclosing a before and after scope capture photo of pin 8 of the LME49724. The first photo is the circuit as is and the second picture is with everything the same except the LME49724 was replaced and now is good and looks to pass our tests.
Is there something in the manufacturing process causing a variation on some parts?
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