The **LL431K-T92-R** is a specific variant of the 431 series programmable shunt regulator. These components are widely used in power supply circuits to provide a stable reference voltage or to act as an error amplifier. --- ### 1. General Specifications The LL431K is a three-terminal adjustable regulator with high thermal stability over its operating temperature range. | Parameter | Value | | :--- | :--- | | **Output Voltage ($V_{ref}$)** | 2.495V (Typical) | | **Adjustable Range** | $V_{ref}$ to 36V | | **Sink Current Capability** | 1.0mA to 100mA | | **Dynamic Impedance** | 0.22 $\Omega$ (Typical) | | **Package Type** | TO-92 | | **Temperature Range** | -40°C to +125°C | --- ### 2. Pin Configuration (TO-92) The TO-92 package typically follows this pinout (verify with the specific manufacturer datasheet as orientations can vary): 1. **Reference (REF):** Input to the internal error amplifier. 2. **Anode (A):** Connected to the negative rail/ground. 3. **Cathode (K):** Connected to the positive rail through a resistor. --- ### 3. Key Features * **Precision:** Provides a highly accurate 2.495V internal reference. * **Low Noise:** The output exhibits low wide-band noise. * **Programmable:** By using an external voltage divider, the output voltage can be set to any value between 2.5V and 36V. * **Temperature Compensation:** Designed to maintain stability despite fluctuations in ambient temperature. --- ### 4. Application Circuit (Example) To calculate the output voltage ($V_{out}$) when using two resistors ($R_1$ and $R_2$): ```cpp // Voltage Formula V_out = V_ref * (1 + R1 / R2) + I_ref * R1 ``` *Note: Since $I_{ref}$ is very small (typically 2-4 $\mu$A), it is often neglected in basic calculations.* --- ### 5. Common Use Cases 1. **Switch Mode Power Supplies (SMPS):** Used on the secondary side for voltage feedback via an optocoupler. 2. **Voltage Monitoring:** Acts as a comparator for over-voltage or under-voltage detection. 3. **Constant Current Source:** Can be configured to regulate current instead of voltage.