## Overview of the VIPER114XSTR The **VIPER114XSTR** is a high-voltage converter belonging to the **VIPerPlus** family manufactured by STMicroelectronics. It is an integrated offline switcher designed for high-performance SMPS (Switched-Mode Power Supplies). It combines an 800 V avalanche-rugged Power MOSFET with a PWM (Pulse Width Modulation) controller. --- ### Key Technical Specifications | Feature | Specification | | :--- | :--- | | **Drain-Source Voltage ($V_{DSS}$)** | 800 V | | **RDS(on)** | 6.0 $\Omega$ (typical) | | **Switching Frequency** | 60 kHz (fixed) | | **Peak Drain Current** | 0.4 A | | **Package** | SSOP10 | | **Supply Voltage Range ($V_{CC}$)** | 4.5 V to 30 V | --- ### Core Electronic Components & Functions The device integrates several critical electronic sub-systems into a single silicon chip: 1. **800 V Power MOSFET**: The high-voltage power stage allows the device to handle large input voltage spikes and operate directly from a rectified AC mains supply (85 VAC to 265 VAC) without external power transistors. 2. **Embedded PWM Controller**: It manages the switching cycle based on feedback, ensuring stable output voltage. It features **jittering** technology, which spreads the EMI (Electromagnetic Interference) spectrum, making it easier to comply with interference regulations. 3. **High-Voltage Start-up Circuit**: Includes an internal high-voltage current source that charges the $V_{CC}$ capacitor during start-up. Once the device is running, the internal source turns off to reduce power consumption (Ultra-low standby consumption < 10 mW at 230 VAC). 4. **Error Amplifier**: Contains an integrated E/A with a 1.2 V reference, allowing for direct feedback sensing without needing an external shunt regulator (like a TL431) in non-isolated topologies. --- ### Integrated Protection Features The VIPER114XSTR is designed to be "rugged," meaning it includes several internal safeguards: * **Pulse-by-Pulse Current Limiting**: Protects the MOSFET from over-current by limiting the peak current in every switching cycle. * **Hysteretic Thermal Shutdown**: Automatically shuts down the device if the junction temperature exceeds safe limits ($~150^\circ C$). * **Overvoltage Protection (OVP)**: Monitors $V_{CC}$ to prevent damage during feedback loop failures. * **Soft-Start**: Reduces mechanical and electrical stress on components during the initial power-up phase. --- ### Typical Application Circuit The VIPER114XSTR is commonly used in **Buck**, **Buck-Boost**, and **Flyback** converters for small appliances, IoT devices, and home automation. ```c // Simplified Pinout Description (SSOP10) Pin 1 (GND) : Ground Pin 2 (NTC) : Temperature sensing or extra protection Pin 4 (FB) : Feedback input for regulation Pin 5 (VCC) : Supply voltage for the control logic Pin 7-10 (DRAIN): High voltage drain of the internal MOSFET ```