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Texas Instruments ups sample rate on industrial measurement ADCs


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DALLAS, TX. (November 9, 2004) ” Providing a breakthrough combination of DC accuracy and AC performance, Texas Instruments Incorporated (TI) (NYSE: TXN) today announced the industry's widest bandwidth 24-bit industrial analog-to-digital converter (ADC). The ADS1271 offers 50kHz bandwidth, 1.8uV/C offset drift and up to 109dB signal-to-noise ratio (SNR), enabling a new level of precision measurements in industrial, medical and automotive applications. (See http://www.ti.com/sc04230.)

Traditionally, industrial delta-sigma ADCs offering good drift performance used digital filters with large passband droop, resulting in limited signal bandwidth mostly suited for DC measurements. High-resolution ADCs for audio applications offer larger usable bandwidths, but the offset and drift specifications are significantly worse (and often unspecified) than their industrial counterparts. The ADS1271 combines these two converter types, allowing high-precision measurements with excellent DC and AC specifications ensured over a -40C to +105C temperature range.

“Texas Instruments has utilized its expertise in precision industrial and high-performance audio data conversion to develop a new class of data converters with unmatched precision and speed,” said Gregg Lowe, senior vice president of TI's high-performance analog business. “This breakthrough data converter provides our customers with the best of both worlds, allowing them to achieve uncompromised performance in their applications.”

Utilizing proprietary design techniques, the high-order, chopper-stabilized modulator achieves very low drift (less than 1.8uV/C) with low in-band noise (6.5uV rms). The onboard linear phase decimation filter suppresses modulator and signal out-of-band noise, providing a signal pass-band of 90% of the Nyquist rate with less than 0.005dB of ripple.

Three selectable operating modes allow for optimization of speed (105kSPS data rate), resolution (109dB SNR) and power dissipation (35mW). A selectable frame-sync or SPI serial interface provides for convenient interfacing to DSPs and microcontrollers. All operations, including internal offset calibration, are controlled directly by pins ” there are no registers to program.

The ADS1271 is optimized to work with TI's high-performance TMS320 DSP platforms. TI also has a range of amplifiers, such as the OPA2227 and OPA1632, which are well suited to work with the ADS1271 to achieve highest performance.

Availability and Packaging

The ADS1271 is sampling now, with volume production scheduled for 4Q 2004. The device comes in a TSSOP-16 package and is priced at $5.90 in 1,000 piece quantities (suggested resale pricing). Evaluation modules (EVMs) are also available.

TI offers analog engineers a wide-ranging support infrastructure that includes training and seminars, design tools and utilities, technical documentation, evaluation modules, an online KnowledgeBase, a product information hotline and a comprehensive offering of samples that ship within 24 hours of request. For more information on TI's complete analog design support, and to download the latest Data Converter Selection Guide, visit www.ti.com/analog.

San Francisco — Texas Instruments will use the electronica convention this week to announce a data converter with extremely high resolution and a record-breaking sample rate. Targeted at industrial applications like weight scales and vibration analysis, the ADS1271 offers a 24-bit resolution with dc accuracy. But — unlike other data converters with this kind of dc accuracy — this device offers a 50 kHz sampling rate.

Existing 12- and 14-bit data converters (used in communications) are capable of sampling signals at up to 100 MHz rates. 16-bit converters (used in audio applications) can sometimes sample at up to 1 MHz rates, but these converters are typically not accurate enough for dc measurements. A 24-bit, dc-accurate converter is typically capable of resolving only one-or-two samples per second. Thus, a dc-accurate device capable of sampling at a 50 kHz rate represents something of a breakthrough.

The combination of speed-and-accuracy embodied in the ADS1271 is obtained by marrying a sigma-delta modulator, ordinarily used for audio signal sampling, with a precision analog front end, explained Texas Instruments' marketing manager Jim Todsen. The analog front end is calibrated and chopped-stabilized, he said.


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Chopper stabilization is a technique that corrects for input offset and drift by commutating input readings between unknown and known values (stored in a capacitor) and averaging tem over a lengthy period of time. Thus, the ADS1271 can retain an offset to within 1.8 uV/C [[microvolt per degree C]] ? effectively 2 ppm over its 5-V input range. .

Targeted at factory environments, as well as automotive applications, the device is specified for industrial temperature ranges of -40 to +105 degrees centigrade. In machine tools, the ADS1271 would not measure the “raw position” of a rotating shaft, Todsen explained, but the “health” of the rotating shaft, such as the almost undetectable wear on bearings and joints. Generators in electric power plants must be failsafe over 100s of thousands of hours, he reminded. A 24-bit device could detect minute but significant changes in the angle of the motor shaft from its true position. With a 24-bit accurate device, each LSB (the smallest increment measured) is one part in 2-to-the-24th-power ? one part in 16,777,216. Such resolution is useful in medical measurement applications as well.

Integral non-linearity of the ADS1271 is specified to within 0.0005 percent of the full scale value – less than 100 LSB over its 5-V input range. SNR (signal to noise ration) is better than 105 dB.

The ADS1271 offers an SPI interface serial interface for microcontrollers, or a frame-synch output for DSPs. The output data rate is a function of the sampling rate. A 50 kHz rate, for example, will yield a 100 ksamples/s data output. A 25 kHz sampling rate yields a 50 ksamples/s data stream. In use, the device allows tradeoffs between resolution, speed and power consumption. Power consumption will vary between 92 and 35 mW, depending on sample rate.


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This price is priced at $5.95 in 1,000-piece lots.

The see more, go to TI’s ADS1271 website. If you want to see the datasheet, click here.

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