**The AD2S90AP: A Comprehensive Guide to Resolver-to-Digital Conversion**

In the world of precision motion control, accurately determining the position and speed of a rotating shaft is paramount. This is where **resolver-to-digital converters (RDCs)** play a critical role, bridging the gap between robust analog sensors and modern digital systems. The **AD2S90AP from Analog Devices** stands as a seminal and widely adopted integrated circuit in this category, offering a reliable and high-performance solution for critical applications.

**Understanding the Resolver and the Need for Conversion**

A resolver is an analog electromechanical transducer that outputs analog signals (SIN and COS) representing the sine and cosine of the shaft angle. Renowned for their **exceptional ruggedness, reliability, and high noise immunity**, resolvers are the sensor of choice in harsh environments like aerospace, military, and industrial automation. However, their analog outputs are incompatible with the digital processors that control the systems. An RDC like the AD2S90AP performs the essential function of converting these sinusoidal and cosinusoidal voltages into a precise digital representation of the angle.

**Key Features and Architecture of the AD2S90AP**

The AD2S90AP is a 10-bit monolithic RDC that distinguishes itself through simplicity and effectiveness. Its operation is based on a **Type II tracking loop architecture**, which is renowned for its ability to continuously track the input angle without the need for complex software algorithms. This closed-loop system ensures **near-instantaneous tracking of the shaft position** with minimal latency, a crucial factor for high-performance servo systems.

Key specifications that define its performance include:

* **10-Bit Resolution:** Providing 1024 distinct positions per revolution, suitable for a wide range of applications.

* **±2.5 Arc Minutes Accuracy:** Ensuring extremely precise angular measurement.

* **Tracking Rate up to 1040 RPS:** Capable of handling very high-speed rotations.

* **Single +5V Supply Operation:** Simplifies power supply design and reduces system complexity.

* **Robust Input Circuitry:** Designed to handle the variable amplitudes and harmonics typical of resolver signals.

**Typical Application Circuit**

Implementing the AD2S90AP requires a minimal number of external components. The circuit typically involves connecting the resolver's outputs (SIN, COS, and reference excitation) directly to the converter's input pins. The chip requires an external **resolver-to-digital conversion** is managed entirely on-chip. The digital output is provided through a **3-state output latch** in a natural binary format, making it easy to interface with a microcontroller or digital signal processor (DSP).

**Advantages and Common Use Cases**

The primary advantage of the AD2S90AP is its **simplicity and reliability**. As a self-contained tracking converter, it offloads the computational burden from the system's main processor. Its robustness makes it ideal for demanding sectors:

* **Aerospace and Defense:** In flight control systems, radar antenna positioning, and gyro stabilization.

* **Industrial Automation:** For precision motor control in CNC machines, robotics, and servo drives.

* **Automotive:** In advanced electric power steering (EPS) systems and other critical vehicle controls.

**ICGOODFIND**

The AD2S90AP remains a foundational component in motion control systems, valued for its **proven tracking architecture, high noise immunity, and straightforward implementation**. It effectively solves the critical interface challenge between analog resolvers and digital controllers, ensuring accurate and reliable operation in the most demanding environments. For designers seeking a robust, no-fuss solution for resolver-to-digital conversion, the AD2S90AP continues to be an excellent choice.

**Keywords:**

Resolver-to-Digital Converter (RDC)

Tracking Loop

Shaft Angle

Noise Immunity

Analog Devices