The **SHT40-AD1F-R2** is a high-precision digital temperature and humidity sensor manufactured by **Sensirion**. It belongs to the 4th generation of Sensirion’s humidity sensors (SHT4x series), designed for high-volume consumer and industrial applications. --- ### 1. Key Technical Specifications The SHT40 is built on a CMOSens® chip, which integrates the sensor element and processing electronics on a single silicon die. | Parameter | Specifications | |:---|:---| | **Supply Voltage (VDD)** | 1.08 V to 3.6 V | | **Average Current** | 0.4 µA (at 1 Hz measurement rate) | | **Idle Current** | 80 nA | | **Interface** | I2C (Standard, Fast Mode Plus, High Speed) | | **Operating Range** | 0 to 100% RH; -40°C to +125°C | | **Accuracy (RH)** | ±1.8% RH (typical) | | **Accuracy (Temp)** | ±0.2°C (typical) | | **Package** | 4-pin DFN (1.5 x 1.5 x 0.5 mm) | --- ### 2. Electronic Architecture The internal circuitry of the SHT40 consists of several critical stages: 1. **Sensing Element:** A capacitive humidity sensor and a bandgap temperature sensor. 2. **ADC (Analog-to-Digital Converter):** Converts the analog signals from the sensors into high-resolution digital data. 3. **Digital Processing Unit:** Handles calibration data, linearization, and temperature compensation. 4. **I2C Interface:** Communicates with the host microcontroller (MCU). 5. **Integrated Heater:** A built-in power-programmable heater used to remove condensed water or perform self-tests. --- ### 3. Pin Configuration The SHT40-AD1F-R2 uses a compact 4-pin DFN package: | Pin | Name | Description | |:---:|:---:|:---| | 1 | **SDA** | Serial Data (I/O) | | 2 | **SCL** | Serial Clock (Input) | | 3 | **VDD** | Supply Voltage | | 4 | **VSS** | Ground | --- ### 4. Communication & Addressing The "AD1F" in the part number designates the I2C addressing and behavior: * **I2C Address:** 0x44 (7-bit). * **Command Set:** Supports various measurement modes (High, Medium, and Lowest precision) and heater activation commands. ### 5. Application Circuit A typical implementation requires minimal external components: * **Pull-up Resistors:** Usually 2.2 kΩ to 10 kΩ on the SDA and SCL lines. * **Decoupling Capacitor:** A 100 nF capacitor between VDD and VSS to filter power supply noise. ---