## Electronic Overview: AD5165BUJZ100-R2 The **AD5165BUJZ100-R2** is a high-performance Digital Potentiometer (DigiPot) manufactured by Analog Devices. It is designed to replace mechanical potentiometers in applications requiring precise, automated, and compact circuit adjustments. --- ### 1. Key Technical Specifications | Feature | Specification | | :--- | :--- | | **Part Number** | AD5165BUJZ100-R2 | | **Resistance (End-to-End)** | 100 kΩ | | **Resolution** | 256 Positions (8-bit) | | **Interface Type** | 3-Wire SPI Compatible | | **Operating Voltage** | 2.7 V to 5.5 V | | **Temperature Coefficient** | 35 ppm/°C | | **Package** | 8-Lead TSOT-23 (Surface Mount) | | **Wiper Memory** | Volatile (Resets on power-off) | --- ### 2. Functional Components The device consists of three primary functional blocks: 1. **Resistor Array:** A string of 256 individual resistors connected in series. The "100" in the part number indicates the total resistance across this string is 100 kΩ. 2. **Digital Interface (SPI):** A Serial Peripheral Interface that allows a microcontroller (MCU) to send 8-bit data words to select the desired wiper position. 3. **Wiper Switches:** Electronic switches (usually MOSFETs) that connect the wiper terminal (W) to one of the nodes in the resistor string based on the digital input. --- ### 3. Pin Configuration (TSOT-23) | Pin Name | Function | Description | | :--- | :--- | :--- | | **VDD** | Power Supply | Positive supply (2.7V to 5.5V). | | **GND** | Ground | Circuit ground. | | **W** | Wiper Terminal | The "moving" contact of the potentiometer. | | **A** | Terminal A | One end of the resistor string. | | **B** | Terminal B | The other end of the resistor string. | | **SDI** | Serial Data Input | Data bit stream from the MCU. | | **CLK** | Serial Clock | Synchronizes the data transfer. | | **CS** | Chip Select | Enables/Disables communication with the chip. | --- ### 4. Implementation Example To set the resistance between Terminal B and the Wiper (W), the following formula is used: ```c // Calculation for resistance at the wiper (Rw) // D = Digital Code (0 to 255) // Rab = Nominal Resistance (100k) // Rw = Wiper Resistance (approx 50-100 ohms) R_wb = (D / 256) * Rab + Rw; ``` --- ### 5. Application Areas * **LCD Contrast Control:** Adjusting the bias voltage for displays. * **Programmable Filters:** Tuning the cutoff frequency of analog filters. * **Gain Control:** Replacing fixed resistors in Op-Amp circuits to create programmable gain amplifiers (PGA). * **Sensor Calibration:** Automated nulling of offsets in bridge sensors.