## SHT45-AD1B-R2 Technical Overview The **SHT45-AD1B-R2** is a high-precision digital humidity and temperature sensor manufactured by **Sensirion**. It belongs to the 4th generation (SHT4x) of CMOSens® technology sensors, designed for ultra-low power consumption and high reliability in demanding environments. --- ### 1. Key Technical Specifications | Parameter | Specification | Note | | :--- | :--- | :--- | | **Interface** | I2C (Standard, Fast, Fast-mode Plus) | Digital communication | | **Supply Voltage (Vcc)** | 1.08 V to 3.6 V | Compatible with 1.8V, 2.5V, 3.3V | | **Supply Current** | 0.4 µA (Average), 80 µA (Idle) | Ultra-low power | | **RH Accuracy** | ± 1.0 %RH | Best-in-class precision | | **Temp Accuracy** | ± 0.1 °C | Range: 20°C to 60°C | | **Operating Range** | 0-100% RH, -40°C to 125°C | Full environmental range | | **Package** | 4-pin DFN (1.5 x 1.5 x 0.5 mm) | Extremely small footprint | --- ### 2. Core Electronic Components & Features The SHT45 is not just a sensor element but an **Integrated Circuit (IC)**. It contains several functional blocks: * **Capacitive Humidity Sensor:** A polymer-based dielectric that changes capacitance based on relative humidity. * **Bandgap Temperature Sensor:** A precision silicon-based sensor for thermal measurement. * **Analog-to-Digital Converter (ADC):** Converts raw analog signals from the sensors into high-resolution digital data. * **Integrated Heater:** A software-controllable power heater used to drive off condensation or test the sensor’s integrity (useful in high-humidity environments). * **I2C Interface (Address 0x44):** The "AD1B" part of the suffix signifies the specific I2C address and behavior (Address 0x44 is the standard). --- ### 3. Pin Configuration (DFN-4) The device uses a 4-pin surface mount design, making it ideal for compact PCB layouts. | Pin Number | Name | Description | | :--- | :--- | :--- | | 1 | **SDA** | Serial Data (I/O) | | 2 | **SCL** | Serial Clock (Input) | | 3 | **VDD** | Supply Voltage | | 4 | **VSS** | Ground | --- ### 4. Application Circuit Example To integrate the SHT45 into a microcontroller system, pull-up resistors are required on the I2C lines. ```cpp // Typical I2C connection logic [Microcontroller] [SHT45] VCC (3.3V) <-----------> VDD GND <-----------> VSS SDA <--[Rp]--> SDA (Rp = 2.2k - 10k Ohm) SCL <--[Rp]--> SCL ``` ### 5. Why the "R2" Suffix? The **R2** indicates the packaging format, specifically **Tape & Reel** (typically 2,500 pieces per reel). This is standardized for automated Pick-and-Place assembly in high-volume manufacturing. ---