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I know this is probably a broad question, but actually I am hoping for a broad answer in this case.

I have a microcontroller for which I need some external SDRAM memory. Let's say the memory's density and configuration is supported by the given microcontroller. Does the package type and number of pins (i.e. 86-pin TSOP or 90-Ball TF-BGA) still matter or can I just choose whatever is cheaper/smaller/fits the PCB?

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closed as unclear what you're asking by Chris Stratton, Finbarr, Edgar Brown, Sparky256, Whit3rd Feb 17 at 11:26

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ If you need one of the pins that the 86-pin package leaves out, then you'll need the 90-pin one. Other than that I'm pretty sure the two should be identical. \$\endgroup\$ – Hearth Feb 11 at 12:10
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    \$\begingroup\$ Apart from the above: I would do trail PCB layout (paper & pencil) to see how easy/difficult the routing is. \$\endgroup\$ – Oldfart Feb 11 at 12:51
  • \$\begingroup\$ External RAM on a microcontroller is very rare, typically by the time that much memory is needed one is more in the territory of an SoC which is often cheaper. \$\endgroup\$ – Chris Stratton Feb 11 at 15:27
  • \$\begingroup\$ @ChrisStratton unfortunately that decision is not for me to make \$\endgroup\$ – nilleeee Feb 11 at 15:38
  • \$\begingroup\$ What you are trying to do, and your question about it puts your project in an odd corner of the possibility space. Designing a board with external memories, especially something like SDRAM, is typically only a project that should be undertaken by the experienced - in which case there would be an awareness that while there are a lot of concerns you need to consider in interfacing an SDRAM with a processor, the package matters only in how it might influcence those, not in an of itself. Your other question indicates the basics of SDRAM are still unfamiliar, this project may be a bit premature. \$\endgroup\$ – Chris Stratton Feb 11 at 16:16