## Overview of the TL432-AF5-R The **TL432-AF5-R** is a precision programmable shunt regulator diode. It is essentially an adjustable zener diode that offers high thermal stability and wide operating current ranges. It is widely used in power management circuits to provide a stable reference voltage. --- ### 1. Key Technical Specifications The "AF5-R" suffix typically refers to the package type (SOT-25/SOT-23-5) and the tape-and-reel packaging. | Parameter | Value / Range | | :--- | :--- | | **Reference Voltage ($V_{ref}$)** | 1.24V (Standard for 432 series) | | **Output Voltage Range** | $V_{ref}$ to 18V | | **Cathode Current ($I_k$)** | 0.1mA to 100mA | | **Reference Input Current** | 1.5µA to 3µA | | **Operating Temperature** | -40°C to +125°C | | **Package Type** | SOT-25 / SOT-23-5 | --- ### 2. Internal Functional Blocks The device integrates several discrete functions into a single silicon chip to maintain high precision: * **Error Amplifier:** Compares the voltage at the REF pin with the internal 1.24V bandgap reference. * **Internal Reference:** A temperature-compensated stable 1.24V source. * **Output Transistor:** A robust bipolar transistor capable of sinking up to 100mA of current to maintain regulation. --- ### 3. Pin Configuration (SOT-25) | Pin Number | Name | Description | | :---: | :--- | :--- | | 1 | **REF** | Reference voltage input | | 2 | **Cathode** | The "positive" terminal (connected to load/resistor) | | 3 | **Anode** | The "negative" terminal (usually connected to Ground) | | 4 / 5 | **NC** | No internal connection (specific to 5-pin variants) | --- ### 4. Typical Applications The TL432-AF5-R is versatile and can be found in: * **Switch Mode Power Supplies (SMPS):** Used on the secondary side for optocoupler feedback loops. * **Voltage Monitoring:** Acting as a comparator with a precision threshold. * **Adjustable Current Sources:** Combined with a pass transistor to regulate current. * **Precision Voltage Reference:** Replacing standard Zener diodes for better temperature drift performance. --- ### 5. Calculation Formula To set the output voltage ($V_{out}$), two external resistors ($R1$ and $R2$) are used in a potential divider configuration: ```text Vout = Vref * (1 + R1 / R2) + (Iref * R1) ``` *(Note: Since $I_{ref}$ is very small, the second part of the equation is often ignored for general calculations.)*