I mean, some parts can only be so small. 0.4mm bga is about as small as things practically get. Is there a specific functionality that you’re looking for?
And if it helps, I’ve done tear downs of pacemakers before where minimizing volume is obviously super crucial. They all use custom silicon.
Really small microcontrollers is one category. There's the ATTiny20 and PSOC4000 ones but what else is hiding out there? DC-DC boosts is another - I've found a few that are sub 1x1 but it would be good to be sure I've found everything in that size category to help make an educated decision on what to use.
Searching Digikey by package area isn't easy. Some vendors have the option but it isn't universal.
Basically, I'm trying to figure out if there's a better approach to finding these parts across vendors.
Honestly, in that scenario, I usually just select all the footprints I don't recognize in the part selector on Digikey and browse through the images. There's usually only a few pages to go through if you've specified everything else well enough.
Also, if you have the means, I remember seeing a demo from TI(?) where they could bond raw silicon in an inner layer of a PCB. So like, buck converter or whatever inside the board and passives immediately above/below it.
Oh, and on that note, I think they sell some BGA parts that are basically just that. Here's an example: https://www.ti.com/product/TPS826716 The controller is inside the little PCB with the passives sitting on top.
Have you tried just setting the search in Digikey to BGAs or CSP chips?
LPC11A04UK,118 claims 2.55x2.55
STM32G071EBY6TR claims 2.3 x 2.4mm
STM32G031Y8Y6TR claims 1.86x2.14mm.
Etc. etc.
All I did was select CSP from 36 pins and less. After that, you look through the "Supplier Device Package" section on the far right and that tends to have the dimensions.
No need to sort: there's only 42 of them. Look through all of them, pick out the ones that are small enough and focus on those.
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