EFM8SB1 Datasheet, PDF (39/55 Pages) Silicon Laboratories – The EFM8SB1 highlighted features are listed below

7.3 CSP16 Package Marking
EFM8SB1 Data Sheet
CSP16 Package Specifications
PPPP
TTTT
YYWW
Figure 7.3. CSP16 Package Marking
The package marking consists of:
• PPPP – The part number designation.
• TTTT – A trace or manufacturing code.
• YY – The last 2 digits of the assembly year.
• WW – The 2-digit workweek when the device was assembled.
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