U3212

U3212 is a high-performance, low-cost PWM control power switch designed for off-line low-power buck applications, featuring a simple peripheral circuit with minimal component count. The device integrates a high-voltage startup module and a high-voltage-rated MOSFET, enhancing the system's surge withstand capability. Unlike conventional PWM power switches, the U3212 has no internal fixed clock to drive the MOSFET; instead, the switching frequency automatically adjusts in response to load variations. The IC 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 is automatically adjusted based on actual load conditions, significantly reducing standby power consumption under no-load state. The U3212 integrates comprehensive self-recovering protection features, including VDD undervoltage lockout, cycle-by-cycle current limiting, output overvoltage protection, overtemperature protection, overload protection, and VDD overvoltage protection. This product family supports off-line non-isolated buck and buck-boost topologies, suited for small appliance power supplies and linear power supply replacement applications, with the advantages of high output accuracy and low peripheral cost.

Applications

• Telecom 90V power systems
• Ethernet PoE
• Industrial control
• Inverter systems

Key features

• Integrated 5A 200V MOS and 200V high-voltage startup circuit
• Multi-mode control for quiet operation
• Supports buck and buck-boost topologies, default 12V output (FB pin floating)
• Standby power consumption below 50mW
• Excellent line regulation and load regulation
• Integrated soft-start circuit
• Integrated overload protection (OLP)
• Integrated cycle-by-cycle current limiting (OCP)
• Integrated output overvoltage protection (OVP)
• Integrated VDD overvoltage, undervoltage, and voltage clamp protection
• Ultra-low quiescent current, typical 200μA
• High-voltage startup circuit with ultra-low standby power consumption (<50mW)
• Cycle-by-cycle peak current limiting with leading-edge blanking
• Multi-mode PWM control (FM and AM combined)
• Integrated soft-start, typical 4ms
• Output overvoltage protection (OVP)
• Overload protection (OLP) / short-circuit protection (SLP)
• Abnormal overcurrent protection (AOCP), typical threshold 0.9V
• Integrated overtemperature protection (OTP), typical trigger junction temperature 150℃
• Optimized fast dynamic response to minimize output voltage drop during load transients