The **SHT40-AD1B-R3** is a high-precision digital temperature and humidity sensor manufactured by **Sensirion**. It is part of the fourth-generation (SHT4x) series, designed for high-volume applications with low power consumption and high reliability. --- ### 1. Key Technical Specifications Below are the primary electronic and performance characteristics: | Parameter | Specification | Notes | | :--- | :--- | :--- | | **Supply Voltage (VDD)** | 1.08V to 3.6V | Ideal for battery-powered devices | | **Interface** | I2C (Standard, Fast, Plus) | Supports up to 1 MHz | | **RH Accuracy** | ±1.8% RH | Typical at 25°C | | **Temp. Accuracy** | ±0.2°C | Typical from 0°C to 75°C | | **Operating Current** | 80 µA (Average) / 0.22 µA (Idle) | Extremely low power | | **Package Type** | 4-pin DFN | 1.5 x 1.5 x 0.5 mm³ | | **I2C Address** | 0x44 | Default address for the AD1B variant | --- ### 2. Functional Electronic Components The SHT40 integrates several electronic systems into a single CMOS chip: #### A. Sensing Elements * **Capacitive Humidity Sensor:** Uses a polymer dielectric that changes capacitance based on ambient humidity. * **Band-gap Temperature Sensor:** Measures temperature variations through precise voltage drops across PN junctions. #### B. The Integrated Circuit (ASIC) * **16-bit ADC:** Converts analog signals from the sensors into high-resolution digital data. * **Calibration Memory:** Each sensor is individually calibrated at the factory; calibration coefficients are stored in non-volatile memory and applied automatically. * **Integrated Heater:** Contains an internal power-programmable heater used to remove condensed water or perform self-tests in high-humidity environments. --- ### 3. Pin Configuration The device uses a 4-pin Dual Flat No-leads (DFN) package: | Pin | Name | Description | | :--- | :--- | :--- | | 1 | **SCL** | Serial Clock (I2C) | | 2 | **SDA** | Serial Data (I2C) | | 3 | **VSS** | Ground (GND) | | 4 | **VDD** | Supply Voltage | --- ### 4. Application Circuit Example A typical circuit requires minimal external components, primarily pull-up resistors for the I2C lines and a decoupling capacitor. ```cpp // Typical I2C Pull-up Resistance Selection: // VDD = 3.3V -> Rp = 10kΩ (Standard Mode) // VDD = 1.8V -> Rp = 2.2kΩ (Fast Mode Plus) [Microcontroller] [SHT40] SDA <----(Rp)------> SDA (Pin 2) SCL <----(Rp)------> SCL (Pin 1) GND <--------------> VSS (Pin 3) 3.3V <---(C=100nF)--> VDD (Pin 4) ``` --- ### 5. Part Number Breakdown * **SHT40:** Base model (4th Generation, Standard accuracy). * **AD1B:** Specifies the I2C address (0x44) and the output characteristics. * **R3:** Indicates the packaging format (Tape & Reel, 10k pieces per reel).