IEEE Solid-States Circuits Magazine - Winter 2022 - 42

Matsuzawa's key realization was that
interpolation significantly lowers the differential
nonlinearity of the ADC because it is intrinsically a
smoothing operation.
statements. Although the companies
represented were then in competition
for a share of the growing consumer
market for camcorders, the
speakers at this rump session wanted
to tell their counterparts about what
they were doing and why as well as
argue for the technical merits of their
chosen architecture. Perhaps this
instinct to share was a residue of the
sentiment, as Japan industrialized
after World War II, that competition
among companies is good but must
be superseded by the goal of uplifting
Japan.
I also remember that, while Matsuzawa
might have struggled a little
with spoken English, lubricated by
the aids to spontaneous discussion
then customary in Japan, he was
uninhibited in provoking the others
with his chosen approach. The audience
loved it. This may well have
been one of his first appearances
before an international audience.
To understand what the excitement
was about, I must relate some
background on video cameras [1]. The
first consumer devices with a built-in
videotape recorder were introduced
in 1984 by JVC, Hitachi, Sony, and
Panasonic (then a brand name of Matsushita
Electric). By 1987, Japan was
producing 4.6 million video cameras
annually, all with charge-coupled
device (CCD) imagers. In 1988, the
year of this symposium, this number
would rise to 6.68 million cameras
annually. It would peak in 2005 at
13 million units manufactured annually
by Japanese companies. As one
point of comparison, Japanese automakers
produced 9 million passenger
cars that year.
At the time of this rump session,
video recording consisted of analog
waveforms in TV signal format captured
on magnetic tape. Why the
fuss, then, over low-power ADCs
of 8-10-b resolution and 10-MHz
signal bandwidth? Consumer electronics
companies wanted to differentiate
their products with new
features. In 1982, T. Yamashita,
the CEO of Matsushita Electric, had
committed the company as part of a
10-year plan to advance four areas
for future products [2]. In descending
order of scope, they were office
automation (Japanese
language
word processors, high-resolution
displays, and printers), robots,
videodisks, and a camcorder with
built-in image stabilization.
We have now almost forgotten
how irritating home videos could
be in the early days because of the
natural shake of the hand that held
the camera. Handheld broadcast
cameras used high-end inertial
TABLE 1. THE INFORMAL CONGRESS OF ADC DESIGNERS
IN A RUMP SESSION AT THE 1988 SYMPOSIUM ON VLSI CIRUITS
(R-5: VIDEO SIGNAL A/D CONVERTERS).
Yasuhiro Sugimoto (organizer)
Toshiba
Asad Abidi (moderator)
Masao Hotta
Yoji Yoshii
Masayuki Ishikawa
Tetsuya Iida
Akira Matsuzawa
42 WINTER 2022
University of California, Los Angeles
Hitachi
Sony
NTT
Toshiba
Matsushita Electric
IEEE SOLID-STATE CIRCUITS MAGAZINE
sensing to detect shake and compensate
for it with a motor [1]. However,
it became clear that nonprofessional
users of camcorders would welcome
an all-electronic motion compensation.
This can only be realized with
a frame memory that enables the
calculation of
fast-changing differences
in successive frames, at the
rate of the shaking of the human
hand. That, in turn, requires that the
image is digitized. Then, after the
motion has been compensated for by
subtracting the calculated motion,
the image is converted back into an
analog waveform for recording. [In
later generations, fuzzy logic (a Japanese
favorite) would be employed to
distinguish between the shake of the
hand holding the camera and natural
movements of the subject.] Thus,
there was a need for low-power, lowcost,
video-rate ADCs and digital-toanalog
converters.
Of the A/D architectures discussed
by participants in this rump
session, Matsuzawa advocated the
use of a flash ADC. To lower its
power to what is acceptable for
battery-operated consumer equipment,
he had developed methods of
interpolation that could reduce the
number of comparators drastically
over a full flash. His key realization
was that interpolation significantly
lowers the differential nonlinearity
(DNL) of the ADC because it is
intrinsically a smoothing operation.
This is especially important in video
encoding because it is well known
that the human eye is sensitive to
abrupt changes in the intensity of
even a single pixel in an image field,
called sparkles.
Matsuzawa says that he designed
and fabricated the first single-chip
flash ADC in Japan, announced in
1981. This is quite an accomplishment
since TRW LSI Products announced
its 8-b, 30-MS/s ADC in 1979, the first
single-chip flash developed in the
United States.
In 1990, Matsuzawa introduced
resistor interpolation into a 10-b,
two-step flash ADC [3],
thereby
employing two methods to lower
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