Reverse-engineering a vintage power supply chip from die photos

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

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

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?

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!

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'.

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 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!!!

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)

Too much complexity without any benefit (when adjusted for new failure cases and cost of additional components and complexity).

Electronics is mostly KISS, not only motivated by the financial factor but also reliability, manufacturing, etc.

So far micro controllers are too expensive, too sensitive to unstable power supply, too complex in general (requiring some support components in some cases, have an additional prefabrication step for flashing firmware by the chip vendor, and cost a lot more.

There is no clear advantage to the approach you mentioned.

Before switching ICs became ubiquitous it was common to roll your own with an 8-bit micro. It isn't cost effective now because of the additional external components, board area, and NRE you'd need vs the single chip solution.

Well, your ARM-powered chip will need some analog-to-digital converters since the feedback signals are analog. And you'll need a high-current output driver to control the switching transistor. And some sort of startup circuit to provide power before the processor starts running. And an undervoltage lockout circuit to prevent the processor from malfunctioning if the voltage drops. So you still have a bunch of analog circuitry but you've added an analog-to-digital converter and a microcontroller. There are some applications where this tradeoff makes sense, but in a lot of cases it would just be excess complexity.

I've come across a broken laptop before that had a complex power control computer like what you've described.

I ended up repairing it by hard-resetting the NVRAM and forcing the power control computer back to its initial "reset" state.

This was a common enough problem that the manufacturer had a step-by-step guide showing how to fix it on their website.

The moral of the story is that adding complexity, even when that complexity is designed to increase robustness, usually just means that there are more systems that can fail.

You can use an MCU as a controller. Here's an example.

https://youtu.be/m8rK9gU30v4

The problem is that you can't make every controller with an MCU, and you can't always make a competitive controller with an MCU.

There are already controller ICs that are configurable. In fact, modern controllers are a mix of analog and digital hardware. They do everything an MCU would do in that situation, but faster, less invasively, and with less power. Often, they do more than an MCU because they're not slowed down by an instruction cycle.

See my comment before last for an example of a software-configurable hardware controller.

Condition monitoring is a thing, and it's done with MCUs, DSPs, and FPGAs. But controllers sit on the non-isolated side of the gate driver, where they have basically no physical access to any useful signals. That's why condition monitoring is separate.

The lookup table idea is used for motor control. It's called a firing angle table. But that's a slower application.

TI makes some DSP chips with a dedicated peripheral (basically just a high resolution timer with some fancy capture/compare units) for doing PWM for power supplies.

Supposedly it can also detect shoot-through and modify timing to compensate.

This is definitely happening in onboard power management for systems with batteries. I suspect it's just big generic PSUs that stick to old analog ASICs.

Not self-tuning, though, they have to be tuned and all that software written.

Dedicated PMIC chips will be mixed signal, with digital control and analog failsafes.