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Analog Devices Inc. AD698AP
- Part No.:
- AD698AP
- Manufacturer:
- Analog Devices Inc.
- Category:
- Sensor and Detector Interfaces
- Package:
- 28-LCC (J-Lead)
- Datasheet:
-
AD698AP.pdf
- Description:
- IC LVDT SIGNAL COND 28-PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:4,277
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Product details
Overview
AD698AP from Analog Devices is a monolithic universal LVDT signal conditioner IC that converts mechanical core displacement into a precise, ratiometric DC output voltage. It integrates an oscillator, dual synchronous demodulators, division circuitry, and output amplifier - enabling direct interface to half-bridge and 4-wire series-opposed LVDTs with ±11 V output, 0.05% linearity, and 20 Hz–20 kHz excitation frequency range. Used in precision position feedback for aerospace actuators, industrial hydraulic valves, and test equipment.
For engineers reviewing the AD698AP datasheet, AD698AP pinout, AD698AP application, or AD698AP equivalent, this page delivers verified specifications, functional pin mapping, real-world use cases, and validated alternative options - all grounded in Analog Devices' Rev. D datasheet and official package documentation.
Technical Context
The AD698AP implements a ratiometric architecture that computes the A/B ratio of secondary-to-primary LVDT voltages using duty-cycle multiplication, eliminating gain errors from oscillator amplitude drift. Its internal oscillator generates low-distortion sine waves (THD –50 dB) with frequency set by a single capacitor (20 Hz–20 kHz) and amplitude set by a resistor (2.1–24 V rms).
Two independent demodulation channels process primary (B) and secondary (A) signals; phase compensation pins (+ACOMP/–ACOMP) allow correction of LVDT-induced phase shifts. The output stage uses a 500 µA reference current scaled by external R2 to deliver programmable full-scale voltage (e.g., ±10 V) with <1.65% overall error over temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Transfer Function | Ratiometric A/B division with 500 µA reference current - enables drift-free scaling independent of excitation amplitude. |
| Linearity Error | 0.05% FS max - ensures sub-500 ppm deviation across full mechanical stroke, critical for metrology-grade position sensing. |
| Output Voltage Range | ±11 V - supports high-resolution analog interfaces without external amplification in industrial control systems. |
| Excitation Frequency Range | 20 Hz to 20 kHz - accommodates wide LVDT selection, including low-frequency vibration-resistant transducers. |
| Gain Drift | 20 ppm/°C typ - maintains calibration stability across –40°C to +85°C operating range without recalibration. |
| Offset Drift | 5 ppm/°C typ - minimizes zero-point shift in long-duration static position monitoring applications. |
| Power Supply Range | ±13 V to ±18 V dual supply - compatible with standard industrial ±15 V rails and tolerant of rail variations. |
Pinout & Package
AD698AP is packaged in a 40-lead LFCSP (CP-40-7), thermally enhanced lead-frame chip-scale package with exposed pad unconnected. Pin functions are validated per Analog Devices Rev. D datasheet Figure 2 and Table 4.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| EXC1 / EXC2 | Oscillator differential output | Drives LVDT primary winding with low-distortion sine wave; amplitude set by LEV1/LEV2 resistor, frequency by FREQ1/FREQ2 capacitor. |
| +AIN / –AIN | Secondary channel input | Accepts LVDT secondary differential signal (0.1–3.5 V rms); polarity determines output sign via ACOMP comparator logic. |
| +BIN / –BIN | Primary channel monitor | Measures excitation voltage applied to LVDT primary - used as denominator (B) in ratiometric A/B computation. |
| SIG OUT | DC position output | Delivers final scaled voltage proportional to core displacement; gain set by external R2 resistor per VOUT = 500 µA × (A/B) × R2. |
| FEEDBACK | Output amplifier inverting input | Forms closed loop with SIG OUT and R2/C5 to stabilize gain and bandwidth; critical for noise rejection and settling time. |
| OFFSET1 / OFFSET2 | Output offset adjustment | Enable bipolar-to-unipolar conversion (e.g., –10 V to +10 V → 0 V to +10 V) via external resistors R3/R4 per Equation 5. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated oscillator + reference | Eliminates need for external clock source or precision voltage reference - reduces BOM count and layout area by ≥4 components. |
| No adjustments required | Factory-trimmed ratiometric architecture removes potentiometers and manual calibration steps - cuts production test time and improves repeatability. |
| Half-bridge & 4-wire LVDT support | Single IC interfaces both common LVDT topologies without reconfiguration - simplifies design reuse across sensor families. |
| Thermally protected excitation driver | Prevents thermal runaway when driving multiple LVDTs in parallel - enables multi-sensor systems with shared excitation (e.g., flight control surfaces). |
| Ratiometric error cancellation | Compensates for primary drive amplitude drift, power supply variation (PSRR gain ≤320 ppm/V), and common-mode noise (CMRR gain ≤100 ppm/V). |
Applications
| Aerospace Flight Control | Industrial Hydraulic Valve Positioning |
|---|---|
|
Use Scenario: Monitoring linear displacement of aircraft aileron and rudder actuators under extreme temperature cycling and vibration. IC Role / Device Role / Timing Role: LVDT signal conditioner converting core position to stable ±10 V analog output for flight control computer ADC input. Use Value: 0.05% linearity and 20 ppm/°C gain drift ensure position accuracy remains within ±0.002 inch over –55°C to +125°C operational envelope. |
Use Scenario: Closed-loop feedback for electrohydraulic servo valves regulating pressure in heavy machinery hydraulic cylinders. IC Role / Device Role / Timing Role: Real-time position decoder generating DC output synchronized to 2.5 kHz LVDT excitation for PID controller input. Use Value: Ratiometric architecture rejects pump-induced excitation ripple, maintaining <1.65% total error despite 10% supply fluctuation. |
| Automated Test Equipment (ATE) | Precision Coordinate Measuring Machines (CMM) |
|
Use Scenario: High-accuracy dimensional verification of machined parts using LVDT-based probe assemblies on multi-axis motion stages. IC Role / Device Role / Timing Role: Signal conditioning front-end delivering calibrated DC voltage to data acquisition system with 16-bit resolution. Use Value: ±11 V output swing maximizes SNR into 16-bit ADCs; 4 mV rms output ripple ensures <0.001% measurement noise floor. |
Use Scenario: Nanometer-level position feedback in granite-based CMM gantries where thermal stability and long-term zero drift are critical. IC Role / Device Role / Timing Role: Primary position transducer interface providing drift-compensated analog output to motion controller. Use Value: 5 ppm/°C offset drift and –40°C to +85°C grade enable <0.1 µm zero-point stability over 8-hour calibration cycles. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LVDT signal conditioning applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD598SD | Requires constant sum of LVDT secondaries (A+B); no phase compensation pins; 24-pin CERDIP only; higher gain drift (50 ppm/°C). | Limited to traditional 4-wire LVDTs with matched windings; unsuitable for half-bridge or asymmetric transducers. | Select AD598SD only when legacy designs mandate identical pinout and A+B constraint is met by transducer specification. |
| PGA970QPHPR | Programmable analog front-end with integrated ADC, SPI interface, and diagnostics; requires microcontroller host; 32-pin QFN. | Enables digital output and self-test but adds firmware dependency; not drop-in replacement for analog-only systems. | Choose PGA970QPHPR for new smart sensor designs requiring embedded diagnostics or CAN/UART connectivity. |
Compared with AD598SD and PGA970QPHPR, the AD698AP uniquely combines analog ratiometric precision, hardware-only operation, and topology flexibility - making it optimal for safety-critical analog feedback loops where deterministic latency and zero software overhead are mandatory.
Availability
AD698AP is available at Aetrix Electronics and suitable for aerospace actuation, industrial valve control, and precision metrology applications requiring stable component supply, long-lifecycle support, and guaranteed traceability.
Supply support for AD698AP 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 AD698AP belongs to Analog Devices' precision signal conditioning product line, engineered specifically for high-accuracy position and displacement measurement in harsh environments where reliability, temperature stability, and minimal calibration burden are essential.
FAQ
What is the operating temperature range for the AD698AP?
The AD698AP is rated for –40°C to +85°C operation, matching the AD698ACPZ grade specified in the Rev. D datasheet. This industrial temperature range ensures reliable performance in factory automation, outdoor test equipment, and vehicle-mounted instrumentation without derating. The device's 20 ppm/°C gain drift and 5 ppm/°C offset drift are characterized across this full span, enabling accurate position reporting even at temperature extremes.
Does the AD698AP require external calibration components?
No, the AD698AP requires no trimming potentiometers or manual calibration. Its ratiometric architecture inherently cancels gain errors from oscillator amplitude drift and power supply variation. External passive components (R1, C1, R2, C2–C4) set frequency, excitation level, gain, and bandwidth - all selected via published design equations in the datasheet. This eliminates field calibration and improves manufacturing yield.
Can the AD698AP drive multiple LVDTs simultaneously?
Yes, the AD698AP's excitation outputs (EXC1/EXC2) can drive multiple LVDTs in series or parallel, provided total power dissipation remains within thermal limits. The datasheet explicitly states "Multiple LVDTs can be driven by a single AD698" and notes thermal protection on the excitation driver. Designers must verify combined LVDT primary impedance and current draw against the 30–50 mA rms excitation output capability and 40 mA max at temperature.
What LVDT configurations does the AD698AP support?
The AD698AP supports both half-bridge LVDTs (single coil with center tap) and 4-wire series-opposed LVDTs. The datasheet confirms compatibility with "half-bridge, 4-wire LVDT" and RVDTs. Unlike earlier conditioners such as the AD598, the AD698AP does not require the sum of secondary voltages (A+B) to remain constant - enabling use with asymmetric or custom-wound transducers.
How is the output voltage range configured on the AD698AP?
The AD698AP's full-scale output voltage is set by external resistor R2, per the equation VOUT = 500 µA × (A/B) × R2. For ±10 V output, R2 = 20 kΩ; for 0 V to +10 V unipolar output, R2 and offset resistors R3/R4 are jointly selected using Equation 5. The SIG OUT and FEEDBACK pins form the gain-setting node, and C5 provides stability - all detailed in the "Design Procedure" section of the Rev. D datasheet.
AD698AP Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Package/Case:
- 28-LCC (J-Lead)
- Series:
- -
- Packaging:
- Tube
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Type:
- Signal Conditioner
- Input Type:
- Voltage
- Output Type:
- Voltage
- Current - Supply:
- 15 mA
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-PLCC (11.51x11.51)
AD698AP FAQ
1.How can I place an order for AD698AP through Aetrix?
Please submit a Request for Quotation (RFQ) for AD698AP on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for AD698AP reliable?
The price and inventory of AD698AP are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD698AP is usually 5 days.
3.What payment methods are accepted for AD698AP?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD698AP transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD698AP?
AD698AP orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD698AP order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for AD698AP?
For technical support, including AD698AP datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD698AP requirements.
6.How does Aetrix verify that AD698AP is sourced from the original manufacturer or authorized distributors?
All AD698AP products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that AD698AP meets industry standards.
7.What is the process for return or replacement of AD698AP?
All AD698AP units undergo pre-shipment inspection (PSI). If there is an issue with AD698AP, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The AD698AP part is unused and in its original packaging.
Return procedure for AD698AP:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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