The **81N45-R-AB3-I-R** is a specific part number typically associated with a **Voltage Detector IC** manufactured by **UTC (Unisonic Technologies Co., Ltd)**. These devices are used for monitoring power supply voltage levels and providing a reset signal to microprocessors. ### 1. Part Number Breakdown The nomenclature for this series (UTC 81Nxx) usually follows this structure: | Segment | Code | Meaning | | :--- | :--- | :--- | | **Series** | 81N | CMOS Voltage Detector | | **Voltage Threshold** | 45 | 4.5V Detection Voltage | | **Output Type** | R | Built-in Delay Circuit (N-Channel Open Drain) | | **Package** | AB3 | SOT-89 Package | | **Data Flow** | I | Halogen Free / Lead Free | | **Packing** | R | Tape & Reel | --- ### 2. Technical Specifications The device is designed for low power consumption and high accuracy voltage monitoring. * **Detection Voltage ($V_{DET}$):** 4.5V (Fixed) * **Operating Voltage Range:** 1.0V to 15.0V * **Low Current Consumption:** Typically 1.0µA to 3.0µA * **Output Configuration:** N-channel Open Drain * **Detection Accuracy:** ±2% * **Hysteresis Characteristic:** Typically $V_{DET} \times 0.05$ --- ### 3. Key Functions and Applications This IC serves as a "watchdog" for the power supply to ensure digital systems do not operate under unstable voltage conditions. #### Primary Functions: 1. **Reset Generation:** It provides a reset signal to a CPU/MCU during power-up. 2. **Low Battery Detection:** In portable devices, it triggers an alert when the battery drops below 4.5V. 3. **System Reliability:** Prevents data corruption by halting operations if the voltage dips (Brown-out protection). #### Common Application Circuit: ```text Vdd (Source) | [Resistor] (Pull-up for Open Drain) | +------- Out (To MCU Reset Pin) | [81N45 IC] | GND ``` --- ### 4. Comparison with 81C Series While the **81N** series features N-channel Open Drain outputs, the **81C** series features CMOS outputs. The "N" version is often preferred when the output needs to be level-shifted or when multiple detectors share a single reset line (wired-OR logic).