Are the physical dimensions of the chip listed somewhere in the article? I'm looking but haven't yet found them.

At the beginning you say "this very small chip", and it would be cool to include the actual dimensions. This will make it possible to get a sense for the size of the features from the magnified die picture.

p.s. You write some of the best articles, I love the way you break things down and present them in an approachable way. Thank you, Ken!

I didn't take measurements, but I think the feature size is about 20 micrometers, which is huge compared to nanometers in modern chips.

Your blog is incredibly well done, and it is always worth my time (several times over) to read what you post. Thank you!

Just want to say thanks for these thorough teardowns and wonderfully annotated die photos.

The Visual 6502 project is what originally inspired me to look inside integrated circuits and see how they really work. Although ICs seem like mysterious black boxes, you can see what's going on. At least until about 1980, and then it gets too complicated for me :-)

http://www.visual6502.org/JSSim/

What are the challenges in reverse engineering more modern chips?

PS awesome blog!

The main problem is Moore's Law, so everything gets smaller and smaller. The old chips I look at have a single metal layer, which makes it much easier to see what's going on. And then in the 1990s, feature sizes got smaller than the wavelength of light so my optical microscope can't see the features.

Would there be any benefit other than cost to analog power control chips like this rather than DSP controlled power supplies like we typically see today?

I'd imagine that their better response latency is eaten up by downstream capacitors anyway. Maybe they'd have better dynamic range to allow them to converge on a clean signal better than a stream of digitized samples that are always probably little off converged one way or the other by some quantum?

I'll be the first to admin that power control isn't my forte though, and most arguments I can come up absolutely sound like the specious stuff you hear out of 'audiophiles'.

Even MCU controlled SPS often times have pure analog control loop, where A/D and MCU is there mostly there for monitoring and perhaps digital control of some loop parameters, but the software is not an integral part of the loop itself...

Which is perhaps for the good, if you look for example on the boost topology, where saturation of the inductor leads to the shorting of the input through a switching transistor to the ground... :)

Here's an interesting video series describing such a software-configured, hardware-controlled switching controller.

Here, Microchip markets this particular line of PIC MCUs as a "field-programmable switch-mode power controller". But weirdly I haven't seen that language on their main site.

https://mu.microchip.com/getting-started-with-cip-hybrid-pow...

DSPs are more expensive to engineer than these tried and tested chips. If you need the functionality of a DSP then you use one but the core performance of a power supply is relatively unaffected.

Have you performed any teardowns and analysis of any similar but newer chips? If so, how does architecture and manufacture compare? Have there been any significant changes in state-of-the-art over the last two decades?

I've looked at more modern power supplies like a Macbook charger [1]. One difference is they have power factor correction in the frontend. Another difference is they use more advanced power supply topologies, such as a resonant converter. Also, efficiency is a bigger concern.

As far as the chips themselves, I haven't looked at a modern power supply controller chip, but I've looked at other power chips [2]. The biggest difference is they are CMOS instead of bipolar. They are also much more complex and dense, so I can't reverse engineer them with my microscope.

[1] https://www.righto.com/2015/11/macbook-charger-teardown-surp...

[2] https://www.righto.com/2020/05/tiny-transformer-inside-decap...

> They are also much more complex and dense, so I can't reverse engineer them with my microscope.

What would be the path forward if you chose to try an do that? A different light frequency microscope? Or something way more complex and expensive?

(Or would having the imaging capability not matter because the complexity is too high even if you could see it properly?)

I love your work, ever since the first time I saw one of your IC RE posts I felt really humbled and inspired by it so I'd like to take this opportunity to thank you for doing it.

Thanks!!!

Several months ago, I started reading every new article. This is the first comment I have left in a few weeks.

Your posts are fantastic, not only do we get a peek inside, but we learn about how electronics work, and why designers make choices.

Thanks!!!

Maybe someone else can chime in, but two questions:

* How do you know if the base silicon is N-doped or P-doped? (does it matter?)

* Why are the layouts of NPN and PNP so different? I’ve seen many die photos and you can (usually) easily tell which transistor is which.

* Lastly, are there any guides on learning how to decipher a die shot into a “schematic”? How do I know which colors mean what? (they vary between IC)

(if it’s not obvious, I’m still learning about this stuff)

The book "The Art of Analog Design" discusses the layouts of components in detail. It says (p280) that theoretically you could make a PNP transistor like an NPN transistor in reverse, but the characteristics of the dopants don't work well for this. Boron diffuses rapidly so it doesn't work well for a buried P layer. And boron only has 1/3 of the solid solubility of phosphorus. The other issue is that the mobility of holes is only 1/3 that of electrons in silicon, so there's an inherent disadvantage for PNP.

I'm kind of guessing that the substrate silicon is P-type since that seems to be more common. As for the colors, each IC is different. There are charts relating colors to thickness, but that doesn't really help me.

N type and p type have different resistance so to get a balanced transistor you need different area proportions of each. If memory serves that is.

Holes have lower mobilty than electrons, so P-doped areas must be larger for the same equivalent resistance.

just a thanking note, for I never had the idea of inspecting power electronics under the hood :)

do you think recent GaN power adapters have very different power ICs ?

I haven't looked into GaN power adapters. I think they use the same control ICs but GaN transistors, but I'm not sure. Maybe someone else here knows more?

The supporting ICs are the same. For now, at least.

But because of differences between GaN and Si, the selection of reasonably compatible controllers and gate drivers is smaller. For example, many ICs made for Si are underperformers for GaN, or they might need some "translation" circuitry because of different gate voltage requirements.

There are certainly many gains to be made with GaN-specific supporting ICs, but that hasn't really happened yet. My personal threshold for acknowledging a fundamentally different technology would be replacing all the Si in the gate drive loop with GaN. The idea is to not hold back the GaN switch from realizing its full potential with slower and less efficient Si.

The GaN switch itself is, of course, quite different from a Si power switch.

Depending on whether you use depletion, or enhancement mode GaN devices. Early GaN devices were JFET, not pure FETs too.

Ones designed with power electronics use in mind are made intentionally close to silicon FETs on specs.