**The AD2S90APZ: A Comprehensive Technical Overview of the Resolver-to-Digital Converter**
In the realm of motion control and high-precision position sensing, the conversion of analog resolver signals into clean, reliable digital data is a critical function. The **AD2S90APZ** from Analog Devices stands as a seminal component in this field, a monolithic resolver-to-digital converter (RDC) that has set a benchmark for performance and reliability. This integrated circuit is engineered to provide a complete, high-accuracy solution for tracking the angular position and velocity of a resolver, which is an analog, transformer-like sensor known for its robustness in harsh environments.
**Core Functionality and Operating Principle**
At its heart, the **AD2S90APZ** performs the complex task of decoding the resolver's output signals. A resolver has a primary winding excited by a sinusoidal reference signal (typically 2 kHz to 20 kHz). Two secondary windings, mechanically shifted by 90 degrees, output sine and cosine signals whose amplitudes are modulated by the shaft's angle (θ). The AD2S90APZ accepts these three signals—**reference (SIN LO), sine (SIN HI), and cosine (COS HI)**—and employs a Type II tracking loop architecture to synchronously demodulate them.
This closed-loop system internally generates a digital estimate of the angle (φ). It continuously compares this estimate to the actual input angle, driving the error to zero. The result is a highly accurate, real-time digital representation of the shaft position with **exceptional noise immunity** and the ability to track very high velocities with minimal lag.
**Key Technical Specifications and Features**
* **High Resolution and Accuracy:** The AD2S90APZ provides a **10-bit digital output** (1024 positions per revolution), with a typical accuracy of ±12 arc-minutes. This resolution is sufficient for a vast array of industrial and automotive applications.
* **Integrated On-Chip Oscillator:** A significant design advantage is its **internal 10 MHz oscillator**, which is used to generate the resolver excitation signal. This eliminates the need for an external clock source, simplifying system design and reducing component count.
* **Velocity Output:** Beyond absolute position, the chip generates a DC voltage (**VELOCITY output**) that is linearly proportional to the motor's speed, providing critical data for velocity control loops without requiring external computation.
* **Robustness and Diagnostics:** The device includes a **Loss of Signal (LOS) detection** circuit. This feature monitors the amplitude of the resolver's inputs and flags a fault condition if the signals fall below a usable threshold, indicating a broken wire or resolver failure—a crucial feature for functional safety.
* **Wide Supply Range and Package:** Operating from a single **+5 V supply**, it is housed in a compact 20-lead PLCC package, making it suitable for space-constrained applications.
**Typical Applications**
The AD2S90APZ is a workhorse in systems demanding precise motion feedback. Its primary applications include:
* **Industrial Motor Control:** Servo drives, robotics, and CNC machinery.
* **Automotive Systems:** Electronic power steering (EPS), throttle control, and advanced suspension systems.
* **Aerospace and Defense:** Actuator control, radar positioning, and flight surface feedback systems where reliability is paramount.
**ICGOOODFIND**
The **AD2S90APZ** remains a classic and highly effective solution for resolver-to-digital conversion. Its **all-in-one monolithic design**, combining the reference oscillator, converter, and diagnostics, offers engineers a simple, robust, and dependable path to acquiring high-fidelity angular data in demanding conditions. For applications where 10-bit resolution is adequate, it continues to be an excellent choice, balancing performance with design simplicity.
**Keywords:**
1. Resolver-to-Digital Converter (RDC)
2. Angular Position Sensing
3. Tracking Loop
4. Monolithic Integration
5. Loss of Signal (LOS) Detection
