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Written by Robo
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Wednesday, 01 April 2009 20:00 |
The ATtiny45 is an 8-bit microcontroller made by Atmel. They are quite popular with the amateur electronics community, and can be found powering lots of home-made gadgets. I received this chip from a friend, who told me he'd accidentally fried it by supplying it with 12 volts instead of 5. He claims it emitted smoke when he did this, but the package doesn't show any burns or stains. Anyway, it's a good opportunity to check out what's inside!
The victim. This one is housed inside an 8-pin DIP package.
The naked chip in all its glory. Let's analyze what we see here: first, there's a thick brown bar just above the centre. This looks like a block of memory, and it's probably the 4 KB of flash memory that holds the main program.
There are also many small blocks scattered around the edge of the chip. These contain circuits that regulate power, provide timing signals, drive external circuitry, etc.
Then there's a lot of dense wiring that covers the bulk of the chip area. This is the digital stuff that makes the chip do its job. The way it's been layed out shows that these circuits have been drawn by a computer. The design team write a lot of computer code (often in VHDL or Verilog), which is then processed and almost directly converted to a circuit layout. This is how nearly all digital circuits are built today. Although it's realistically the only way to design modern high-performance chips, I think it's quite boring: you don't get to play with transistors, you just sit behind a keyboard. And that's exactly the reason why I wanted to be an electronic engineer, rather than a programmer :-)
A close-up of the area at the top. Note that there are a lot of small pieces of metal that cover much of the circuits below. They don't seem to be providing any useful function, so I guess they're just there to obscure the view of the circuits below. The six thick bars at the centre are obviously power supply lines: the come from a large bus on the outside of the chip, and are connected to lots of thinner supply lines below.
The engineers at Atmel have conveniently labelled this area "OSC-2000". So it's safe to conclude that this is the built-in RC oscillator. And indeed it consists of a couple of huge resistors (vertical blue lines) and capacitors (yellowish-green squares).
A couple of test structures that show the process engineers how well they've done. There's also an AVR logo here.
The Atmel logo is located all the way on the other end of the chip.
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