alt Hacker NewsIs there really a microcontroller in there? As in a general purpose microprocessor core executing machine code in ROM? Any references for that?
I find it baffling that this would be cost effective. Maybe by dropping in a CPU core and software you save some design cost vs. a more specialized IC. But it must be more expensive per unit to manufacture in a process where you can fit in all those transistors. And these things are manufactured in such quantities that design costs must be a pretty minimal part of the final part price.
This used to be implemented as a purely analog control loop, i.e. opamps and such. After all TCXOs predate the age of ubiquitous CPUs by decades. Even if there is a need for a factory-programmed temperature calibration curve, there are techniques where it can be implemented in a pure analog way, or in a dedicated digital circuit where the transistor count will be much lower vs. a general purpose CPU core.
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If you implement a temperature-calibration curve by analog means, it will drift in time, unless you use very high-quality and expensive components.
Calibrations done with a microcontroller have replaced those done with analog components in most applications, because the total cost is reduced in this way.
Even a relatively powerful 32-bit ARM microcontroller costs a fraction of a dollar. Good analog components, with guaranteed behavior in temperature and in time, are usually more expensive than microcontrollers.
That microcontroller costs a small fraction of the precision ground crystal it is boxed in with.
You need a way to calibrate the device after the package is sealed, that implies some smarts or you're going to end up with a whole raft of extra pins and that would be costlier than the microcontroller!
I'm sure there are alternative ways but in this day and age cpus and small amounts of flash + memory are priced a little bit above the sand they're made of. I have whole units packaged and with far larger capabilities for $3 Q1, and that's with a whole lot of assembly and other costly detailing.
Microchip, one particular embedded controller manufacturer lists their SMD packaged PIC16F15213-I/SN which is much more powerful than what you need here for $0.33, Q100 that drops to $ 0,27400. This is a complete device, not an unpackaged die, which would retail for a small fraction of that.
Control loops and analog stuff works well, but not if you also want to be able to do calibration after the fact package is sealed, I'm not aware of any tech that would be fully analog but that would have the same flexibility and long term stability, never mind mechanical stability (microphony, talking to a crystal is probably the cheapest and easiest way to get FM modulation!). Note that this is different precision wise from a device that simply measures the temperature and does a compensation based on that, the device you are looking at in this article is easily an order of magnitude better.