## Overview of VIPER115XSTR The **VIPER115XSTR** is a high-voltage converter belonging to the **VIPerPlus** family from STMicroelectronics. It is designed for high-performance offline power supplies (AC-DC conversion). This IC integrates an 800 V avalanche-rugged MOSFET with a PWM controller. ### 1. Key Technical Specifications | Parameter | Value | | :--- | :--- | | **Drain-Source Voltage ($V_{DSS}$)** | 800 V | | **Max Output Current ($I_{Dlim}$)** | 480 mA | | **Switching Frequency** | 60 kHz (Fixed) | | **Operating Supply Voltage ($V_{CC}$)** | 4.5 V to 30 V | | **Package** | SSOP10 | --- ### 2. Main Internal Components The VIPER115XSTR is an "all-in-one" solution that reduces component count by integrating several electronic parts: * **800 V Power MOSFET:** The power stage that handles the high-voltage switching. Its high breakdown voltage provides a significant safety margin against voltage spikes from the AC line. * **PWM Controller:** Manages the switching logic to regulate the output voltage. * **High-Voltage Startup Chain:** Includes an internal high-voltage current source that allows the device to start up directly from the rectified mains, eliminating the need for an external startup resistor. * **Error Amplifier:** Features an integrated 1.2 V reference voltage for precise regulation. --- ### 3. Integrated Protection Features To ensure the reliability of the power supply, the IC includes several automated protection circuits: 1. **Pulse-by-Pulse Current Limiting:** Protects the MOSFET from overcurrent by limiting the peak current in every cycle. 2. **Hysteresis Thermal Shutdown:** Automatically shuts down the IC if the internal junction temperature exceeds safety limits (typically $150^\circ C$). 3. **Overvoltage Protection (OVP):** Monitors the $V_{CC}$ pin to protect the load from voltage surges. 4. **Soft-Start:** Reduces mechanical and electrical stress on components during power-up by gradually increasing the current limit. --- ### 4. Typical Application Circuits The VIPER115XSTR is versatile and supports various power supply topologies: * **Non-isolated Flyback:** Ideal for small appliances where user isolation isn't required. * **Isolated Flyback:** Uses an optocoupler for feedback, providing safety isolation for consumer electronics. * **Buck Converter:** Used for simple DC-DC step-down applications directly from a rectified AC line. --- ### 5. Pin Configuration (SSOP10) | Pin Name | Function | | :--- | :--- | | **GND** | Ground / Source of the internal MOSFET. | | **VCC** | Supply voltage for the control logic. | | **DRAIN** | High voltage drain of the internal MOSFET. | | **FB** | Feedback input for regulation. | | **COMP** | Compensation pin for the error amplifier loop. | | **LIM** | (Optional) Current limit set point adjustment. |