acquisitionZONE Products for the week of March 1, 2004
"With the ADC081000, National is expanding its ADC product offerings into the GHz range with an extremely low-power product that enables our customers to eliminate heat sinks, saving both board space and system cost," said Andrew Jue, director of marketing for National Semiconductor's Data Conversion Systems group. "National's proprietary, analog-optimized 0.18 micron CMOS process enables us to deliver high-performance ADCs with the lowest power consumption in the industry."
The ADC081000 is the first in a family of GHz-range ADCs. It will be
followed by a dual product in the second half of 2004 and higher-speed versions
in 2005.
analogZONE Says . . .
It is quite unnerving in a product release to get more information from the news release than from the data sheet. The latter is a single page with no dynamic numbers quoted.
The ADC081000 is not targeted directly at the MAX108/104 products which have conversion rates of 1.5 Gsample/s and 1.0 Gsample/s because those are both designed for split ±5 V rails and use over 6 W of power: getting some very respectable numbers. No, this National part is directly competitive with Atmel's AT84AD001 1-Gsample/s converter. When, however, National misleadingly says, "requires 75 percent less power than most comparable products on the market" that is directly referring to the Maxim parts and not the Atmel one, which happens to use exactly the same operational power as National at 1.4 W, typical. Atmel uses 3.3 V analog and digital rails (2.5 V for the LVDS outputs) instead of the 1.9 V National is using, so the ADC081000 is drawing rather more current. Power down on the National part consumes considerably less than the Atmel one at 5 mW, typical, instead of 120 mW.
That 1.9-V rail may also be a design nightmare when it comes to chasing down every available dB of SNR. We have no numbers for SINAD and SFDR but they need to be better than 55 dB and -60 dBc to be acceptable. The bandwidth of the sample-and-hold also needs to be better than 2 GHz to find acceptance in many applications.
Like the Atmel part the ADC081000 uses a 1:2 demultiplexer on the output to feed two LVDS buses to halve the sampling rate for the effective data rate.
National quotes that, "The ADC081000 is designed with an extremely low bit error rate (BER)" but does not quote any specification.
Apart from known uses for parts of this speed in test equipment there are some limited applications for 8-bit resolution in direct-conversion receivers, especially satellite, and there is a growing business ahead for emerging radar systems.
It is unfortunate that the ADC081000 has become a token ISSCC product announcement. It deserves better than that.
The ADC081000 is sampling, with production expected in the Summer of 2004, in a thermally-enhanced LQFP-128 and will be priced at $100 in 1000-piece lots.