January 16, 2023

Toshiba 2SK369 - low noise JFET : weekend die-shot

Toshiba 2SK369 - is a classical low noise JFET with high gm0. Similar to BF862 we see lots and lots individual transistors in parallel.
Die size 765x765 µm.

January 1, 2023

Casio-F-91W - iconic quartz watch : weekend die-shot

Casio F-91W is an iconic watch worn (among others) by Barack Obama and Osama bin Laden. While working on precision watch firmware (with quartz temperature compensation, aiming for error of under 10 seconds per year) for SensorWatch which is built around F-91W - I was curious to see how original chip looked like.

Surprisingly, chip is more complicated than I anticipated and digital part is less than ~50% of the die area. F-91W has trim jumpers on the PCB to adjust part-to-part variability of the quartz crystal. Looking at die complexity - it might be that they use capacitive tuning of frequency rather than skipping/adding ticks. Also, it might happen that they even have coarse/cost-efficient temperature compensation. Casio specify accuracy of 30 seconds per month, but some F-91W watches are within 6 seconds per month which requires good adjustment & luck for non-temperature compensated watch.

Latest versions of the watch work 7-10 years on a single battery, while early versions lasted "only" 2 years. While original F-91W was introduced in 1989, this die is designed in 2006. If someone has original version from 1989/early 1990's - it would be interesting to compare if it's a "die shrink" or re-design with improved performance.

You can compare die complexity to Luch quartz watch. It's not a digital watch, but see how much less analog circuitry was there.

Die size 2990x2541 µm.

Pinout suggested by Joey Castillo:
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January 1, 2023

RCA CA3031 - opamp : weekend die-shot

RCA CA3031 is a general-purpose amplifier used in narrow-band and bandpass amplifier, feedback amplifier, dc and video amplifier, multivibrator, oscillator, comparator, servo driver, and scaling adder applications. Designed for asymmetrical power supplies: +12V and -6V. Rated for storage temperature of 200°C. RCA CA3031 is analog of Fairchild µA702.

Die size 1142x1134 µm.

Schematic below:
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November 2, 2022
November 1, 2022

Signetics LM373 - AM/FM/SSB IF strip : weekend die-shot

LM373 is what we could have called "Analog SOC" : most of the components one needed to build AM/FM/SSB radio transceiver.
Die size 1644x1366 µm.

October 22, 2022

SEM selfie : weekend SEM porn

Did you know that you can make Scanning Electron Microscope to see itself? At right acceleration voltage electron beam can charge tiny dielectric sphere or plate to potential of ~30kV, at which point it starts reflecting electrons of lower energies back and allow microscope to see itself. Bright donut in the middle is backscattered electron detector (BSE, all 4 segments are enabled), tiny dark spot in the middle is output aperture where electrons are coming out. BSE detector is brightest here as it directly sees reflected electrons, everything else needs multiple reflections to hit detector.

At clock position 12 - there is energy-dispersive detector aperture, at 2 - secondary electron detector and bias electrode, and 10 - photomultiplier.

Let's see how other detectors looks like:
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