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Data converters support motor control for industrial and automotive applications

Norwood, MA — Feb. 17, 2004 — Analog Devices Inc. introduced a trio of converters for motor control applications that require high precision. These converters solve challenges associated with current and voltage monitoring, optical encoder feedback, and resolver-to-digital conversion. These processes are vital to industrial applications, such as assembly-line robots, and also to automotive applications, such as power-assisted steering, both of which require precise control of motor speed and mechanical movements. The new converters feature some of ADI's best-in-class technologies and include the following:

— The industry's fastest 12-bit, simultaneous-sampling,
successive-approximation (SAR) analog-to-digital converter
(ADC), featuring 2-MSPS throughput and less than half the
power consumption of competitors;

— The industry's first isolated analog to digital converter, incorporating ADI's iCoupler digital
isolation technology, which enables higher speed and accuracy at lower power;

— A completely monolithic resolver-to-digital converter (RDC), offering the best combination of speed, accuracy and functionality in a space-saving design.

1- and 2-MSPS 12-bit SAR
The AD7266 is a simultaneous-sampling, dual-channel, 12-bit SAR (successive approximation) ADC, enabling extremely fast loop-settling time with throughput rates up to 2 MSPS. The IC's analog input architecture and signal ranges are designed to interface with popular, off-the-shelf optical encoders which provide a low-cost, high accuracy solution. Optical encoders are used in servo control applications, such as robots, and turning machines that require shaft feedback to the controller for precise positioning of mechanical movements. The chip consumes 20 mW (less than one half that of any other 2-MSPS simultaneous-sampling ADC on the market, according to the company). A 1-MSPS version–the AD7265 — is also available. The AD7265 and AD7266 are available in 32-lead LFCSP or TQFP packages.

Pricing in 1,000-piece quantities is $5.75 for the AD7265 and $7.55 for the AD7266. The product is sampling now with full production expected in late 2004.

Sigma-Delta ADC for Current Monitoring
The AD7400 and AD7401 provide the ideal isolated sigma-delta solution, featuring 12-bit linearity and sample rates up to 20 MSPS. They are popular choices for current monitoring, which is used to operate myriad motor control applications. In lifts, pumps, and fans, for example, motor speed is controlled by varying the input signal. The integration of ADI's exclusive iCoupler isolation technology allows for isolated, high-speed data rates with low power. The ADC inputs are optimized for monitoring current through shunt resistors, while protecting the digital communication lines with a 3.75 kV reinforced isolation barrier. The converter operates from a 5 V power supply and accepts a +/-200 mV signal range, making it suitable for direct connection to current shunts. The converter's offset drift is 5 microvolts per degree C, half that of competitive solutions. Two versions are available: the AD7400 features an internal clock to minimize external components, and the AD7401 uses an external clock to synchronize multiple converters.

The AD7400 and AD7401 are available in 16-lead SOIC packages and are priced at $4.00 in 1,000-piece quantities. The product is sampling now with full production expected in late 2004.

Resolver-to-Digital Converter
A complete monolithic resolver-to-digital converter (RDC), the AD2S1200 equips designers with a fast (up to 1000 rps), accurate (up to +/- 11 arc minute), fully-integrated, RDC solution for variable speed control applications that require additional power. Automotive applications, such as power-assisted steering systems, and industrial applications where there are large temperature variations, such as glass manufacturing, require robust, resolver-to-digital conversion to ensure stability and precise positioning of mechanical movements in harsh temperature environments. The converter contains a 12-bit resolution tracking resolver and an on-board programmable sinusoidal oscillator that provides sine wave excitation. Other key features include a fault-detection circuit that detects any loss of resolver signals, out-of-range input signals, input signal mismatch, or loss of position tracking. The chip communicates via a 12-bit parallel port or 3-wire serial interface. The resolver also provides an incremental encoder emulation output with 1024 pulses per revolution with additional directional pulse, eliminating the need for external A and B directional decode logic. The device operates from a single 5-V supply, with a temperature range of -40 degrees C to +125 degrees C.

The AD2S1200 is available in a 44-lead LQFP package and is priced starting at $12.00 in 1,000-piece quantities. The part is in full production, with samples now available.

2MSPS SAR AD7266 Data sheet

1MSPS SAR AD7265 Data sheet

Sigma-Delta AD7400/01 Data sheet

RDC AD2S1200 Data sheet

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