Wednesday 27 February 2019

integrated circuit - Which of these marks signifies Pin 1 on the STM32F (LQFP64)?



I'm using the STM32F105, in a LQFP64 package. It has two circular markings, on opposing corners of the IC. This picture is for a different ST ARM, but the markings and silkscreen are similar:


ARM


The larger mark in the upper-right of the picture has a flat bottom, whereas the smaller mark in the lower-left is slightly concave. This package doesn't have an exposed pad, so there are no clipped corners underneath.


The datasheet only mentions one mark:


diagram


and I haven't found any other package documentation that mentions it.


Does anyone have a clue for me?




Update:


The project is completed and the answers are correct. Pin 1 is the smaller, concave mark in the lower-left. Don't forget to upvote the good answers!



Interestingly, I've since purchased another batch of these chips and they only have the one mark. Thanks, all!



Answer



I have designed a board for the STM32F103R, like you. Tested and "proven" now.


Anyway, if the text is right-side-up, pin 1 is in the lower left.


The other answers all mention things that could be considered a "hint", Luckily those hints all point in the same direction and happen to be correct.


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