**AD71056ARZ-RL: Complete Pinout, Technical Specifications, and Application Circuit Design Guide**
The **AD71056ARZ-RL** is a highly integrated, precision analog front-end (AFE) and sigma-delta (Σ-Δ) analog-to-digital converter (ADC) from Analog Devices, designed primarily for high-accuracy measurement applications. This guide provides a detailed overview of its pin configuration, key technical specifications, and a fundamental application circuit design.
### **Complete Pinout**
Housed in a 24-lead SOIC package, the AD71056ARZ-RL's pinout is critical for proper PCB layout and system integration. The pins are logically grouped by function:
* **Power Supply (Pins 1, 2, 12, 13, 24):** `AVDD` (Analog Positive Supply, +5V) and `DVDD` (Digital Positive Supply, +3V to +5V) are separated to minimize digital noise coupling into the analog circuitry. `AGND` and `DGND` (Analog and Digital Ground) should be tied together at a single point close to the device.
* **Analog Inputs (Pins 3-8, 21-23):** The device features two fully differential input channels. Channel 1 uses `AIN1+` (Pin 4) and `AIN1-` (Pin 5), while Channel 2 uses `AIN2+` (Pin 6) and `AIN2-` (Pin 7). `REF IN+` (Pin 21) and `REF IN-` (Pin 22) are for the external differential reference voltage.
* **Serial Interface & Control (Pins 14-20):** This includes a 3-wire serial interface: `SCLK` (Serial Clock, Pin 17), `DIN` (Serial Data Input, Pin 16), and `DOUT` (Serial Data Output, Pin 15). Key control pins are `/CS` (Chip Select, Active Low, Pin 14), `/RST` (Reset, Active Low, Pin 20), and `MODE` (Pin 19) for selecting master or slave clocking.
* **Clock (Pin 18):** The `MCLK` pin is used for the master clock input, which determines the modulator and filter operating frequency.
### **Technical Specifications**
The AD71056ARZ-RL excels in providing high-resolution and low-noise performance.
* **Resolution:** **24 bits (no missing codes)**.
* **Sample Rate:** Programmable, typically up to **500 Hz** for effective 50Hz/60Hz line cycle rejection.
* **Input Channels:** Two fully differential analog input channels.
* **Integral Non-Linearity (INL):** Typically **±0.0015%** of Reading, ensuring exceptional accuracy.
* **Gain Error:** Typically **±0.1%** (programmable to ±0.001% via on-chip calibration registers).
* **Noise Performance:** Features a **programmable gain amplifier (PGA)** with gains from 1 to 128, allowing it to handle very low-level signals from sensors like strain gauges and RTDs. The inherent noise is extremely low, enabling stable readings of small delta signals.
* **Power Consumption:** Typically **1.5 mW** at 3V, making it suitable for portable instruments.
* **Interface:** **Synchronous serial interface** that is easily compatible with most microcontrollers and DSPs.
### **Application Circuit Design Guide**
A typical application for the AD71056ARZ-RL is in a **high-precision weigh scale or bridge sensor measurement system**. The core circuit design focuses on signal integrity and noise reduction.
**Key Design Considerations:**
1. **Power Supply Decoupling:** Place **0.1 µF ceramic capacitors** as close as possible to each `AVDD` and `DVDD` pin, connecting them directly to the respective ground (`AGND`/`DGND`). A larger bulk capacitor (e.g., 10 µF) is also recommended on the supply rail.
2. **Analog Input Filtering:** A simple **RC low-pass filter** (e.g., 100Ω resistor and 0.1 µF capacitor) should be placed in series with each analog input pin (`AINx+`, `AINx-`). This is critical for **anti-aliasing** and suppressing out-of-band RF noise.
3. **Reference Voltage Stability:** The accuracy of the ADC is directly tied to the stability of its reference voltage. Use a **high-precision, low-drift voltage reference IC** (e.g., ADR431) connected to `REF IN+` and `REF IN-`. Decouple it thoroughly.
4. **Grounding:** The single most important layout rule is to use a **star ground configuration**. All analog and digital grounds should meet at one point near the AD71056's `GND` pins. Keep digital traces away from analog signal paths.
5. **Microcontroller Interface:** Connect the `SCLK`, `DIN`, `DOUT`, and `/CS` lines directly to the microcontroller's SPI port. Use a GPIO pin for the `/RST` control. Ensure the `MODE` pin is tied correctly (typically high for master mode).
A basic connection diagram for a single-channel bridge sensor measurement would include the sensor bridge, the input RC filters, the voltage reference, the decoupling capacitors, and the SPI connection to a host microcontroller.
**ICGOOODFIND:** The AD71056ARZ-RL stands out as a premier solution for designers needing **high-resolution, low-noise data conversion** in precision measurement systems. Its integrated PGA, flexible configuration, and excellent DC performance make it an ideal AFE for industrial process control, portable instrumentation, and precision sensor interfaces, simplifying design while maximizing accuracy.
**Keywords:** **Sigma-Delta ADC**, **Analog Front-End (AFE)**, **24-Bit Resolution**, **Precision Measurement**, **Bridge Sensor Interface**.
