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Digital TCXO achieves high accuracy over wide operating temperature range

Sunnyvale, Calif. — The DS4026 digitally-controlled temperature compensated crystal oscillator (DC-TCXO) from Maxim Integrated Products offers a frequency accuracy and stability better than ±1.0 ppm over a wide operating temperature range of 40° to +85°C. Over a 10-year operational life, the device is accurate to better than ±4.6 ppm and provides excellent phase noise performance, with characteristics of -140 dBc/Hz at a 1 kHz offset, which the company claims is the best in the industry.

Maxim attributes the high performance of this digitally tunable TCXO to the use of proprietary design and calibration techniques that negate the effects of electromechanical stress, thermal variations, and frequency perturbations (also known as “activity dips”), which can be excited in all crystal elements as they operate over temperature, and result in a performance degradation in overall system performance, explained Maxim. The system also uses DSP-designed components, which are individually programmed to the specific crystal's element over temperature, voltage, and specific signal quality.

This TCXO supports applications that require an extremely accurate and stable time base such as wireless infrastructure applications, SONET/SDH systems, instrumentation and test systems, and GPS and navigation equipment.

Typically, digital approaches introduce noise components onto the TCXO's output frequency but Maxim uses finite step-compensation methods to overcome this problem of a noisy digital TCXO. The new approach features calibration routines and a proprietary
temperature-controlled crystal loading design. In this design, each DS4026 device is factory calibrated to compensate its embedded crystal's natural temperature characteristics. As a result, the digitally controlled DS4026 achieves the performance typically reserved for analog TCXO designs, said the company.

In addition to providing smooth analog-compensation transition curves, the programmable DSP technique also addresses the industry issues and concerns about activity fluctuations in TCXO products.

The DS4026 digital TCXO also integrates many unique capabilities and features not commonly found on TCXOs, said Maxim. These functions include a ±3 degree Celsius accurate and readable temperature sensor and a 16-bit DSP-controlled DAC for
frequency stability, trimming, and calibration. Frequency trimming and temperature reading are accomplished through an I2C control interface.

The DS4026's frequency can be tuned with a resolution better than 1 ppb and tuning ranges greater than ±10 ppm. The device operates from a 3.3 V ±5% supply voltage and is packaged in a standard 300-mil 16-pin SO. The device is fully
RoHS compliant, and is available in commercial and industrial temperature versions.

Pricing: $20.00 (10k-up, FOB USA).
Availability: Samples are available now.
Product information: DS4026
Datasheet: DS4026

Maxim Integrated Products , 1-800-998-8800, www.maxim-ic.com

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