Analog Devices Inc. AD2S99AP

Overview

AD2S99AP from Analog Devices is a programmable sinusoidal oscillator IC designed to provide precision excitation and synchronous reference generation for resolver, synchro, LVDT, and RVDT transducers. It delivers 2–20 kHz programmable excitation (±10% accuracy over –40°C to +85°C), ±3 V_p-p square-wave SYNREF output phase-locked to SIN/COS inputs, and integrated loss-of-signal (LOS) detection. It serves as the excitation source and dynamic phase compensation engine in high-accuracy angular position sensing systems.

For engineers reviewing the AD2S99AP datasheet, AD2S99AP pinout, AD2S99AP application, or AD2S99AP equivalent, key selection considerations include its 20-pin PLCC package, dual EXC outputs with 180° phase relationship, FBIAS-based intermediate frequency tuning, LOS open-drain logic indicator, and compatibility with AD2S80A/AD2S82A/AD2S90 R/D converters.

Technical Context

The AD2S99AP implements a closed-loop phase detection architecture that dynamically locks its SYNREF output to the phase of incoming SIN and COS feedback signals-enabling real-time compensation for temperature- and cable-induced phase shifts in resolver secondary windings. Its internal sine wave generator drives differential EXC/EXC outputs (2 V_rms, low THD) while supporting four factory-selectable frequencies via SEL1/SEL2 pins.

Frequency programming is achieved through digital pin strapping (2/5/10/20 kHz) or analog fine-tuning via FBIAS resistor-to-VDD connection. The LOS circuit monitors both SIN and COS amplitudes against a 0.6 V_rms threshold and asserts an open-drain high signal when both fall below it-providing fail-safe transducer disconnection detection without external components.

Key Specifications

Pinout & Package

AD2S99AP is housed in a 20-pin Plastic Leaded Chip Carrier (PLCC, package code P-20A) with gull-wing leads. Pins 19 and 20 are internally connected VSS terminals; pins 6 (DGND) and 16 (AGND) must be externally shorted at the device footprint. NC pins (3, 4, 9, 13, 14, 15) are not bonded and must remain unconnected.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar programmable transducer excitation applications.

Compared with AD2S99BP, the AD2S99AP trades initial frequency accuracy for cost efficiency in volume industrial applications; compared with AD2S1210, it preserves analog interface flexibility and simplifies upgrade paths for existing resolver signal chains.

Availability

AD2S99AP is available at Aetrix Electronics and suitable for resolver-based motor control, avionics position sensing, and industrial hydraulic valve monitoring requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for AD2S99AP 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 semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision measurement and control.

The AD2S99AP belongs to Analog Devices' resolver interface product line, engineered specifically to simplify high-accuracy angular position feedback in safety-critical motion systems by integrating excitation, phase compensation, and fault detection.

FAQ

What is the function of the FBIAS pin on the AD2S99AP?

The FBIAS pin on the AD2S99AP enables fine-tuning of the excitation frequency beyond the four factory-set values (2/5/10/20 kHz). By connecting a resistor from FBIAS to VDD, users can achieve intermediate frequencies-e.g., 8 kHz is obtained by setting SEL1/GND and SEL2/VSS (10 kHz base) and adding a 6 kΩ resistor. This feature allows optimization for specific transducer resonance or EMI requirements without changing the AD2S99AP hardware layout.

How does the AD2S99AP implement dynamic phase compensation?

The AD2S99AP implements dynamic phase compensation by continuously comparing the phase of incoming SIN and COS signals from the transducer and adjusting its SYNREF output to maintain zero phase error. This closed-loop operation compensates for temperature-dependent phase shifts in resolver windings and cabling delays-eliminating the need for fixed external phase-lead networks and ensuring consistent accuracy across –40°C to +85°C operating range in the AD2S99AP.

Can the AD2S99AP drive a resolver directly without external amplification?

Yes, the AD2S99AP can drive typical resolvers directly: its EXC/EXC outputs deliver 2 V_rms into a 500 Ω load with 8 mA rms current capability. For low-impedance resolvers (<200 Ω) or long cable runs, an external buffer (e.g., OP279) is recommended-but the AD2S99AP's native drive strength suffices for most industrial and aerospace resolvers without added components.

What is the purpose of the LOS output on the AD2S99AP?

The LOS (Loss-of-Signal) output on the AD2S99AP is an open-drain pin that pulls high when both SIN and COS input amplitudes fall below 0.6 V_rms, indicating transducer disconnection or failure. It requires a 50 kΩ pull-up to VDD and provides immediate hardware-level fault signaling-enabling safety controllers to initiate shutdown or redundancy switchover without software intervention in critical AD2S99AP-based systems.

Which R/D converters are explicitly compatible with the AD2S99AP's SYNREF output?

The AD2S99AP's SYNREF output is explicitly designed to interface with Analog Devices' AD2S80A, AD2S82A, AD2S83, and AD2S90 resolver-to-digital converters. The ±3 V_p-p square wave is phase-coherent with SIN/COS inputs and matches the REF input requirements of these devices-though for AD2S90, a 0.1 µF AC-coupling capacitor and 100 kΩ GND resistor are required per the AD2S99AP datasheet Figure 3.