There are now two sources of analog
front ends (AFEs) for ultrasound applications.
Texas Instruments is sampling the
AFE5805, the first member of a future
family for portable to high-end ultrasound
diagnostic equipment. Last year, Analog
Devices introduced the AD9271 for the
same market. Functionally similar, both
are octal devices that incorporate a lownoise
amplifier, variable gain amplifier
(VGA), anti-aliasing filter, and 12-bit
analog-to-digital converter (ADC).
The TI chip beats the ADI chip in terms
of input-referred noise (1.1 versus 1.3
nV/vHz in CW/Doppler mode, 0.85
versus 1.2 nV/vHz in time-gain control/
imaging mode), VGA gain-control range
(46 versus 30 dB), and power consumption
per channel (122 versus 149 mW).
These values are typical for parts rated
for 40-Msample/s ADC conversion rates.
ADI currently has a version that goes to
50 Msamples/s. The TI datasheet mentions
50 Msamples/s, but contains no
specs for that speed.
That puts TI ahead in the specification
race, but there’s more to the story. The
subtext is about a change in the way medical-
imaging systems are being designed.
Engineers at ultrasound OEMs have until
now used separate boards for analog and
digital subsystems. The presence of two
competitors with mixed-signal devices
points to a market that no longer feels it
needs to roll its own to achieve optimum
performance in the system elements
ahead of the number-crunching circuitry.
The demand for AFEs indicates that
ultrasound OEMs think the IC makers
can do it monolithically as well as or better
than they can with separate chips. This
indicates that the chip makers have been
doing their homework, which in turn
means that medical imaging is a market
worthy of large investments. And medical
imaging is significant because its end markets
are particularly diverse.
Chinese OEMs concentrate on inexpensive
portable units to spread 21st century
diagnostics to an awakening population.
European OEMs focus on high-end
equipment for the most subtle kinds of
diagnostics. Japanese and North American
companies straddle both worlds, trying
to push ever-greater imaging resolutions
and blood-flow measurements into evershrinking
ultrasound boxes for private
clinics and even ambulances.
TI’s AFE5805 comes in a 15- by 9-mm,
135-pin, ball-grid-array package. Suggested
retail price is $75 each in 100s. Samples
and evaluation modules are available now,
with volume production slated for June.
TEXAS INSTRUMENTS • www.ti.com