Battle of octal, mid-speed 12-it ADCs heats up via more low-power, high-performance offerings

Santa Clara, Calif.—Following close behind the octal mid-speed ADC announcement from Texas Instruments (click here), another major analog vendor has announced the first of its own roughly similar converters, but with significant architectural and performance differences as well.

The ADC12EU050 from National Semiconductor is an eight-channel, 12-bit, 50 MSPS analog/digital converter which uses a continuous-time, sigma-delta architecture, and provides alias-free sampling for input signals with up to 25-MHz bandwidth. The 350 mW IC (44 mW/channel; claimed to be 30% less than comparable pipelined architectures) also includes an integral “brick-wall”, low-pass anti-aliasing filter, eliminating the need for external filtering. Primary applications for this converter are portable medical ultrasound instruments, industrial imaging equipment, and other test and measurement units.

The input stages of the channels look purely resistive, thus simplifying drive requirements (no sample-and-hold needed) and handle signals of 2.1 Vp-p . This input range decreases to 1.6 Vp-p if the user switches on the input-overload recovery (IOR) function, which ensures that circuitry recovers from saturation within one clock cycle, a concern in applications where an unexpected, highly reflective obstacle (such as a metal clip) is in the ultrasound imaging path.

The IC operates from a moderate-performance crystal, then uses an internal PLL to develop a low-jitter, high-precision, 800-MHz clock using its PLL and VCO functions. SNR is 70 dB full scale and SINAD (signal-to-noise and distortion) reaches 68 dB. The serialized outputs of the 1.2 V, 10×10 mm, 68-pin LLP IC are compatible with LVDS and SLVS formats.

More product information is available at:

Pricing and availability: $64 each in 1,000 piece quantities, sampling now; volume production 3Q2008.

National Semiconductor Corp.,

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