## SHT40-AD1P-R3 Electronic Overview The **SHT40-AD1P-R3** is a high-accuracy, ultra-low-power relative humidity (RH) and temperature sensor manufactured by **Sensirion**. It belongs to the 4th generation of Sensirion’s humidity sensors, designed for high-volume consumer and industrial applications. --- ### 1. Key Technical Specifications | Parameter | Specification | Notes | | :--- | :--- | :--- | | **Supply Voltage (VDD)** | 1.08 V to 3.6 V | Ideal for 1.8V and 3.3V logic | | **Average Current** | 0.4 µA | At 1 measurement per second | | **Idle Current** | 80 nA | Ultra-low power standby | | **RH Accuracy** | ±1.8% RH | Typical range | | **Temp Accuracy** | ±0.2 °C | Typical range | | **Interface** | I2C (Fast Mode Plus) | Up to 1 MHz communication | | **Package** | 4-pin DFN | 1.5 x 1.5 x 0.5 mm³ | --- ### 2. Internal Electronic Components The SHT40 integrates several critical electronic blocks within its tiny DFN package: 1. **Capacitive Sensing Element:** The humidity sensor utilizes a polymer dielectric that changes capacitance based on ambient moisture. 2. **Bandgap Temperature Sensor:** A specialized silicon circuit that measures temperature with high precision. 3. **ASIC (Application Specific Integrated Circuit):** * **ADC:** Converts analog signals from the sensors to 16-bit digital data. * **Calibration Memory:** Stores factory-calibrated coefficients so the user doesn't need to calibrate the sensor manually. * **Digital Logic:** Manages the I2C communication and power management. 4. **Integrated Heater:** An on-chip power heater used to remove condensation or test the sensor's functionality in high-humidity environments. --- ### 3. Pin Configuration The device uses a standard 4-pin layout, making it easy to integrate into compact PCB designs: | Pin Number | Name | Function | | :--- | :--- | :--- | | 1 | **SDA** | Serial Data (I/O) | | 2 | **SCL** | Serial Clock (Input) | | 3 | **VDD** | Supply Voltage | | 4 | **VSS** | Ground | --- ### 4. Application Circuitry To function correctly, the SHT40 requires minimal external components. A typical implementation includes: * **Decoupling Capacitor:** A 100 nF capacitor placed between VDD and VSS to filter power noise. * **Pull-up Resistors:** Two resistors (typically 10 kΩ for 100 kHz or 2.2 kΩ for 400 kHz/1 MHz) connected to the SDA and SCL lines. --- ### 5. Part Number Breakdown: SHT40-AD1P-R3 * **SHT4x:** Product series. * **AD1P:** Defines the I2C address (0x44) and the output format (Pulse Width Modulation vs. Digital). * **R3:** Refers to the Tape & Reel packaging (3,000 pieces per reel).