U3211

U3211 is a high-performance, low-cost PWM control power device designed for offline low-power buck applications, featuring a simple peripheral circuit with minimal component count. The device integrates a built-in startup module and a high-voltage (650V) MOSFET, enhancing the system's surge withstand capability. Unlike conventional PWM power switches, the U3211 has no fixed internal clock to drive the MOSFET; instead, the switching frequency automatically adjusts according to load variations. The chip employs multi-mode PWM control technology, which effectively simplifies peripheral circuit design, improves line and load regulation, and eliminates audible noise during system operation. In addition, the internal peak current detection threshold automatically adjusts to actual load conditions, significantly reducing standby power consumption under no-load state. The U3211 integrates a comprehensive self-recovering protection mechanism, including VDD undervoltage protection, cycle-by-cycle current limiting, output overvoltage protection, thermal protection, overload protection, and VDD overvoltage protection.

Applications

• Small appliance power supplies
• Industrial control

Key features

• Integrated 650V high-voltage startup circuit
• Multi-mode control for noise-free operation
• Supports buck and buck-boost topologies
• Default 12V output (FB pin floating)
• Standby power consumption below 50 mW
• Excellent line and load regulation
• Integrated soft-start circuit
• Comprehensive built-in protection: overload protection, cycle-by-cycle current limiting, output OVP, VDD OVP/UVP, and voltage clamp protection