Need help identifying PAD and microcontroller

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keithaf
 
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Need help identifying PAD and microcontroller

Post by keithaf »

Image

Anyone recognize this SMT pad type? It strikes me as odd because it's almost just 3-sided?

I'm also trying to identify which microcontroller would sit on this pad.

There's a small footprint microcontroller that sits on it, at least 48-pins, drives a 36-pin LCD, a highly accurate real time clock, has some non-volatile storage built-in, and runs on a single +3V CR2032.

The labeled pins on the board are : vpp, sclk, sdat, ref, out, gnd, inl, inr, and res.

Any chance this is an example of chip-on-board? I know there was epoxy involved, but don't have the knowledge to know if it was a glob-top or what.

Thanks
Keith

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adafruit_support_mike
 
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Re: Need help identifying PAD and microcontroller

Post by adafruit_support_mike »

The crystal right next to the footprint suggests it was some kind of microcontroller. Given the pattern of solder that remains on the traces, I'd guess it was something like a PLCC of DFN package, though it may have been a QFN. The pads don't look like what you'd expect for Chip-On-Board, and I don't see any indiciation of wire bonding.

As for the exact kind of microcontroller, heaven only knows. The board looks like a keyfob, and major consumers like auto manufacturers can get their own private lines of chips.

1chicagodave
 
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Re: Need help identifying PAD and microcontroller

Post by 1chicagodave »

I could be wrong….but the big dark circle-ish shape has me willing to bet it used to look something like this -
RTC_COB
RTC_COB
csem_si-res.jpg (202.1 KiB) Viewed 410 times
GLOB
GLOB
improvefigs3-4.gif (35.91 KiB) Viewed 410 times

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keithaf
 
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Re: Need help identifying PAD and microcontroller

Post by keithaf »

That previous image is absolutely stunning, although I'm not sure how much of a match it is.

Here is the die (a die?) that came off of the microcontroller : unfortunately, this image quality is garbage, but take a look anyways

Image

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adafruit_support_mike
 
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Re: Need help identifying PAD and microcontroller

Post by adafruit_support_mike »

Hunh.. a flip-chip. I was just right enough to be wrong.

Pulling guesses out of thin air, I'll say that yellowish block in the center is a register file, with the CPU living just to its left. To the right lives something that looks like EEPROM, and the block at the bottom looks like SRAM. The blue and yellow regions up top look vaguely like Flash memory, and the sawtooth features below them suggest that the blocks between those and the register file are the address decoders.

The blocks to the left of the CPU will be special-feature circuits, like SPI, I2C, and so forth. The bands around the perimiter of the chip contain the pin IO circuits.

The overall layout makes me think it's a mid-tier chip.. if the lowest end of the product range has 256 bytes of EEPROM and 2k of Flash , this one has 512 and 4k, but don't take the sizes literally. ICs use a lot of cookie-cutter design though, where you design a standard module then copy/paste it to get twice as much of the feature.

Try to get a more focused view of the lower-left corner near the pads.. it looks like there may be some kind of notation there.

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keithaf
 
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Re: Need help identifying PAD and microcontroller

Post by keithaf »

@Mike and others: thanks for the help.

Keith

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