The **TL431G-AE2-R** is a popular adjustable precision shunt regulator. It is often referred to as a "programmable zener diode" because its output voltage can be set to any value between its reference voltage ($V_{ref} \approx 2.495V$) and 36V using two external resistors. --- ### 1. Technical Specifications Below are the key electrical characteristics for the TL431G-AE2-R: | Parameter | Specification | | :--- | :--- | | **Reference Voltage ($V_{ref}$)** | 2.495V (Typical) | | **Output Voltage Range** | $V_{ref}$ to 36V | | **Sink Current Capability** | 1.0mA to 100mA | | **Output Impedance** | 0.2 $\Omega$ (Typical) | | **Operating Temperature** | -40°C to +85°C (Standard) | | **Package Type** | SOT-23-3 (Surface Mount) | --- ### 2. Pin Configuration The "AE2" suffix typically denotes the SOT-23 package pinout. For the TL431G series in this package, the pinout is generally as follows: 1. **Reference (R):** Input used to set the output voltage. 2. **Cathode (K):** The "positive" terminal (similar to a Zener cathode). 3. **Anode (A):** The "negative" terminal/ground. --- ### 3. Key Features & Functionality * **Programmable Output:** By using a voltage divider connected to the Reference pin, the device maintains the Cathode voltage such that the Reference pin stays at 2.495V. * **Temperature Stability:** It features low temperature drift, ensuring the voltage remains stable across varying environments. * **Fast Turn-On:** It has a sharp turn-on characteristic, making it an excellent replacement for standard Zener diodes in many applications. --- ### 4. Application Circuit (Example) To calculate the output voltage ($V_{out}$) based on two resistors ($R_1$ and $R_2$): ```python # The formula for Output Voltage (Vout) # Vout = Vref * (1 + R1 / R2) + Iref * R1 Vref = 2.495 R1 = 10000 # 10k Ohms R2 = 10000 # 10k Ohms Vout = Vref * (1 + R1 / R2) print(f"Calculated Vout: {Vout}V") # Result: 4.99V ``` --- ### 5. Common Use Cases * **Shunt Regulator:** Providing a stable reference voltage for analog circuits. * **Switching Power Supplies (SMPS):** Used in the feedback loop (often paired with an optocoupler) to regulate output voltage. * **Current Limiter:** Configured to monitor current across a sense resistor. * **Voltage Monitoring:** Acting as a comparator to trigger an event when a specific voltage threshold is reached.