AD698AP

Overview

The AD698AP is a monolithic universal LVDT signal conditioner designed to convert mechanical position into unipolar or bipolar DC voltage with high accuracy. It integrates an internal low-distortion sine wave oscillator and voltage reference, eliminating the need for external adjustments. The device supports half-bridge, 4-wire LVDTs, and RVDTs within a 20 Hz to 20 kHz frequency range. Key electrical parameters include a linearity of 0.05%, an output voltage swing of ±11 V, a gain drift of 20 ppm/°C (typical), and an offset drift of 5 ppm/°C (typical). It operates in the -40°C to +85°C temperature range.

Feature Summary

• Integrates all necessary circuit functions on a single chip, including oscillator and voltage reference, requiring only minimal external passive components for frequency and gain setting.
• Employs a unique ratiometric architecture that divides secondary output by primary amplitude to eliminate scale factor errors caused by drive amplitude drift, enhancing temperature stability.
• Features two synchronous demodulation channels to detect primary and secondary amplitudes, enabling accurate decoding of AC bridge signals without manual calibration.

Applications

• Industrial automation systems requiring precise linear displacement measurement
• Robotics applications needing high-reliability position feedback
• Precision metrology equipment utilizing LVDT sensors

Procurement Notes

Verify the specific suffix AP indicates the commercial grade operating from -40°C to +85°C. Confirm package availability matches design requirements, as the device is offered in PLCC and CerDIP formats. Ensure supply chain sources provide original manufacturer documentation to validate authenticity and revision status before integration into production designs.

Selection Notes

Select the AD698AP when operation within the -40°C to +85°C range is sufficient. Consider the AD698SQ variant if extended industrial temperature coverage up to +125°C is required. Evaluate system bandwidth needs against the 20 Hz to 20 kHz operational range. Verify that the required output voltage swing of ±11 V aligns with downstream ADC or amplifier input limits.

Part Context

The AD698 series serves as a complete subsystem for interfacing Linear Variable Differential Transformers. It replaces complex discrete solutions by consolidating excitation generation, demodulation, and scaling into one component. This integration simplifies PCB layout and reduces noise susceptibility compared to multi-chip approaches, making it a standard choice for robust position sensing architectures.

Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided source material. Designers should consult Analog Devices for current obsolescence status or equivalent product recommendations based on specific performance criteria.