The **TL431L-T92-R** is a precision programmable shunt regulator diode. It is widely used in power electronics as a voltage reference or an error amplifier in feedback loops. --- ### 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Reference Voltage ($V_{ref}$)** | 2.495V (Typical) | | **Output Voltage Range** | $V_{ref}$ to 36V | | **Cathode Current ($I_k$)** | 1.0mA to 100mA | | **Tolerance** | Usually ±0.5% or ±1.0% (Grade dependent) | | **Package Type** | TO-92 (T92 suffix) | | **Temperature Stability** | 50 ppm/°C (Typical) | | **Dynamic Impedance** | 0.22 $\Omega$ | ### 2. Part Number Breakdown: TL431L-T92-R Understanding the suffix codes helps in identifying the specific variant: * **TL431**: Base part number (Adjustable Precision Shunt Regulator). * **L**: Often denotes **Lead-free** (RoHS compliant) or a specific low-voltage/low-current grade depending on the manufacturer (UTC, Unisonic, etc.). * **T92**: Indicates the physical package style (**TO-92**), which is a common 3-pin plastic through-hole package. * **R**: Typically refers to the packing method, in this case, **Tape & Reel** (Ammo Pack). ### 3. Internal Pin Configuration (TO-92) When looking at the flat side of the TO-92 package with pins pointing down: 1. **Reference (Ref):** The voltage input used to set the output. 2. **Anode (A):** Connected to the negative rail/ground. 3. **Cathode (K):** Connected to the positive rail through a resistor. ### 4. Common Applications The TL431 is versatile and can be found in: * **Switch Mode Power Supplies (SMPS):** Used with an optocoupler to provide isolated feedback. * **Voltage Monitoring:** Acting as a comparator to trigger an alarm if voltage exceeds a limit. * **Constant Current Sources:** By maintaining a constant 2.5V across a precision resistor. * **Linear Regulators:** Serving as the reference for a pass transistor. ### 5. Simple Calculation Example To set the output voltage ($V_{out}$), a resistive divider is used: ``` Vout = Vref * (1 + R1 / R2) ``` *Where $V_{ref}$ is 2.495V.* ---