The **LL431NSK-AE3-R** is a precision adjustable shunt regulator. It is widely used in power management circuits to provide a stable reference voltage. This specific part number follows the naming convention of manufacturers like **UTC (Unisonic Technologies)**. --- ### 1. Technical Specifications Below are the primary electrical and physical characteristics: | Parameter | Specification | | :--- | :--- | | **Device Type** | Adjustable Precision Shunt Regulator | | **Package Type** | SOT-23 | | **Reference Voltage ($V_{ref}$)** | 2.495V (Typical) | | **Output Voltage Range** | $V_{ref}$ to 36V | | **Sink Current Capability** | 1.0mA to 100mA | | **Reference Accuracy** | ±0.5% or ±1% (Grade dependent) | | **Operating Temperature** | -40°C to +125°C | --- ### 2. Pin Configuration (SOT-23) The device typically uses a 3-pin configuration: 1. **Reference (R):** Sets the output voltage via a resistor divider. 2. **Cathode (K):** The output terminal (connected to the load/pull-up). 3. **Anode (A):** The ground terminal. --- ### 3. Key Functional Features * **Programmable Output:** By using two external resistors, the output voltage can be set to any value between 2.5V and 36V. * **Low Temperature Coefficient:** Ensures the voltage remains stable even as the device heats up. * **Fast Turn-on Response:** Makes it ideal for switching power supplies. * **Low Output Noise:** Provides a clean reference for sensitive analog circuits. --- ### 4. Common Applications The LL431 series is a "workhorse" in electronics, found in: * **Switching Mode Power Supplies (SMPS):** Used in the feedback loop (often paired with an optocoupler) to maintain constant output voltage. * **Voltage Monitoring:** Acting as a comparator for over/under-voltage protection. * **Constant Current Sources:** Configuring the device to regulate current instead of voltage. * **Zener Diode Replacement:** Offers much higher precision and sharper "knee" characteristics than standard Zener diodes. --- ### 5. Part Number Breakdown * **LL431:** Base model (similar to the industry standard TL431). * **NSK:** Specific internal sub-code (often refers to low cathode current or specific accuracy). * **AE3:** Denotes the **SOT-23** package type. * **R:** Indicates **Tape & Reel** packaging for automated assembly.