The **US211HAL-AF5-R** is a high-sensitivity, unipolar Hall Effect Switch integrated circuit (IC) primarily designed for contactless switching applications. It is commonly used in consumer electronics for lid-close detection or proximity sensing. --- ### 1. Key Technical Specifications The following table outlines the primary electrical and physical characteristics of the device: | Parameter | Specification | | :--- | :--- | | **Part Number** | US211HAL-AF5-R | | **Sensor Type** | Hall Effect Switch (Unipolar) | | **Operating Voltage (Vdd)** | 2.4V to 5.5V | | **Output Type** | Open-Drain | | **Magnetic Sensitivity** | High (Typical Operating Point: 30G to 60G) | | **Package Type** | SOT-23-5 | | **Operating Temperature** | -40°C to +85°C | | **Current Consumption** | ~2.5mA (Active) | --- ### 2. Functional Description The US211HAL-AF5-R operates by sensing the magnetic flux density of a South pole magnet. * **Unipolar Operation:** It only responds to a single magnetic pole (usually the South pole). When the magnetic field exceeds the "Operating Point" (Bop), the output transistor turns on. * **Hysteresis:** The device includes built-in hysteresis to prevent "chattering" or output instability when the magnet is hovering at the edge of the sensing range. * **Open-Drain Output:** This requires an external pull-up resistor to define the "High" logic level, allowing for easy interfacing with different microcontroller voltages (e.g., 3.3V or 5V). --- ### 3. Pin Configuration (SOT-23-5) Typical pinout for the AF5 (SOT-23-5) package variant: | Pin Number | Symbol | Function | | :--- | :--- | :--- | | 1 | NC | No Connection | | 2 | GND | Ground | | 3 | NC | No Connection | | 4 | VDD | Power Supply Input | | 5 | OUT | Output (Open-Drain) | --- ### 4. Typical Applications * **Smart Covers:** Detecting when a tablet or smartphone flip-cover is closed. * **Laptops:** Sensing when the lid is closed to trigger "Sleep" mode. * **Limit Switches:** Contactless position detection in industrial machinery. * **Water Meters:** Pulse counting for flow rate measurement using rotating magnets. --- ### 5. Implementation Example To use this part with a microcontroller (e.g., Arduino or ESP32), follow this basic circuit structure: ```cpp // Schematic Logic: // [VDD] --- [10k Pull-up Resistor] --- [OUT Pin] // [OUT Pin] connects to Microcontroller Digital Input void setup() { pinMode(HALL_SENSOR_PIN, INPUT_PULLUP); } void loop() { int sensorValue = digitalRead(HALL_SENSOR_PIN); if (sensorValue == LOW) { // Magnet detected (South Pole present) } } ```