TI brand chips, OPA656N and SOT23-5 are used in one board of our batch products; The principle is shown in the figure below:
When a batch of boards are used, the instrument test performance is poor, as shown in the figure below. It seems that the chip voltage noise is high.
Verification test
When other conditions remain unchanged, the following tests shall be carried out:
(1) The chip OPA656N in this batch of defective boards was replaced with the chip of the earlier product, and the original defective instrument was tested normal;
(2) The chip OPA656N in the defective boards of this batch was welded to the early normal products, and the original normal instrument failed the test;
That is, the bad test of the whole instrument is synchronized with the OPA656N chip of this batch, and the OPA656N chip is the cause of the bad test.
Please help analyze the specific reasons
