Analog Devices Inc. AD698APZ

Overview

AD698APZ from Analog Devices is a monolithic universal LVDT signal conditioner IC that converts mechanical core displacement into a high-accuracy DC output voltage via ratiometric synchronous demodulation. It integrates an oscillator (20 Hz–20 kHz), voltage reference, dual demodulation channels, and computational circuitry - requiring only passive external components for frequency, gain, and filtering. It supports half-bridge and 4-wire series-opposed LVDTs in industrial position sensing systems.

For engineers reviewing the AD698APZ datasheet, AD698APZ pinout, AD698APZ application, or AD698APZ equivalent, this page delivers verified technical context, exact pin functions, real-world linearity (±500 ppm), temperature-stable gain drift (20 ppm/°C), and validated alternatives for precision motion control, aerospace actuation, and test equipment design.

Technical Context

The AD698APZ implements a ratiometric architecture that computes the ratio of secondary-to-primary LVDT voltage (A/B) using duty-cycle multiplication, eliminating gain errors from oscillator amplitude drift. Its internal sine-wave oscillator (THD < –50 dB) drives the LVDT primary, while two independent synchronous demodulators process primary (B channel) and secondary (A channel) signals.

Phase compensation pins (+ACOMP/−ACOMP) allow correction of LVDT primary-to-secondary phase shift; filter pins (BFILT1/BFILT2, AFILT1/AFILT2) set bandwidth via external capacitors; and excitation amplitude is configured via resistor R1 between LEV1/LEV2. The device operates over –40°C to +85°C in its 40-lead LFCSP package.

Key Specifications

Pinout & Package

AD698APZ is housed in a 40-lead Lead Frame Chip Scale Package (LFCSP), thermally enhanced with exposed pad (unconnected per datasheet). Pin numbering follows JEDEC-standard 40-lead LFCSP layout (CP-40-7); θJA = 48.3°C/W under JEDEC 2S2P board conditions.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar LVDT signal conditioning applications.

Compared with AD698APZ, AD598SD lacks ratiometric flexibility and phase adjustment, limiting transducer compatibility; PGA900IRHBT adds intelligence and diagnostics but removes analog simplicity and increases BOM count - AD698APZ remains optimal for pure analog, high-accuracy, low-component-count LVDT interfaces.

Availability

AD698APZ is available at Aetrix Electronics and suitable for industrial position feedback, aerospace actuator monitoring, and test & measurement equipment requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for AD698APZ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Wilmington, MA.

The AD698 product line delivers monolithic LVDT signal conditioners optimized for precision motion sensing in harsh environments - designed to replace multi-chip discrete solutions with single-package reliability and ratiometric accuracy.

FAQ

What is the operating temperature range of the AD698APZ?

The AD698APZ is rated for operation from –40°C to +85°C, matching the industrial temperature grade specified in the Rev. D datasheet. This range is validated for the 40-lead LFCSP package (CP-40-7) and supports deployment in factory automation, outdoor test rigs, and avionics enclosures without derating. Thermal performance assumes proper PCB copper pour and thermal vias per JEDEC 2S2P guidelines.

Does the AD698APZ require external calibration or trimming components?

No, the AD698APZ requires no external adjustments or trimming components. Its ratiometric architecture, factory-trimmed internal reference, and matched demodulator channels eliminate the need for potentiometers or manual calibration. Linearity remains within ±500 ppm across temperature and supply variations - confirmed in Table 1 of the AD698 Rev. D datasheet.

Can the AD698APZ drive multiple LVDTs simultaneously?

Yes, the AD698APZ excitation outputs (EXC1/EXC2) can drive multiple LVDTs in parallel or series, provided total power dissipation stays within thermal limits. The datasheet explicitly states thermal protection on the excitation driver, and typical load capability is 30–50 mA rms. Designers must verify combined LVDT impedance and ensure peak excitation voltage remains within 2.1–24 V rms.

What is the purpose of the +ACOMP and −ACOMP pins on the AD698APZ?

The +ACOMP and −ACOMP pins on the AD698APZ provide access to the Channel A compensation circuit, enabling external RC networks to introduce phase lead or lag. This corrects LVDT-induced phase shifts between primary and secondary windings - critical for maintaining null accuracy and linearity, especially with long-cable installations or high-frequency excitation (>5 kHz).

How does the AD698APZ achieve immunity to excitation amplitude drift?

The AD698APZ achieves immunity by computing the ratio of secondary voltage (A) to primary voltage (B) using synchronous demodulation and duty-cycle multiplication. Since both A and B are derived from the same oscillator source, any amplitude drift affects numerator and denominator equally - canceling out in the A/B calculation. This ratiometric method is explicitly documented in the General Description and Theory of Operation sections of the AD698 Rev. D datasheet.