U322

U322 is a high-performance, low-cost PWM control power device designed for off-line low-power boost, buck, and buck-boost applications, featuring a simple peripheral circuit with minimal component count. The integrated high-voltage MOSFET enhances system surge withstand capability. Unlike conventional PWM controllers, the U322 has no fixed internal clock driving the MOSFET; the switching frequency automatically adjusts with load variations. The chip employs multi-mode PWM control technology to effectively simplify peripheral circuit design, improve line and load regulation, and eliminate audible noise during operation. The internal peak current detection threshold automatically adjusts according to actual load conditions, effectively reducing standby power consumption under no-load conditions. The U322 integrates comprehensive auto-recovery protection features, 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 200V high-voltage startup circuit
• Integrated current-limiting resistor (default 1.2A)
• Multi-mode control, noise-free operation
• Supports boost, buck, and buck-boost topologies
• Default 12.5V output (FB pin floating)
• Standby power consumption below 50mW
• Excellent line regulation and load regulation
• Integrated soft-start circuit
• Internal protection features: overload protection, cycle-by-cycle current limiting, output OVP, VDD overvoltage, undervoltage, and voltage clamp protection
• Ultra-low quiescent current, typical value 200μA
• High-voltage startup circuit and ultra-low standby power consumption (<50mW)
• Cycle-by-cycle peak current limiting and leading-edge blanking (blanking time ~300ns)
• Multi-mode PWM control (combined frequency and amplitude modulation)
• Soft-start time typical value 4ms
• Output OVP (triggered when FB pin voltage exceeds 2.4V for 3 consecutive cycles)
• Overload protection/short-circuit protection (with anti-false-trigger logic)
• Abnormal overcurrent protection (AOCP, typical threshold 0.9V)
• Over-temperature protection (auto-restart mode when junction temperature exceeds 150℃)
• Optimized dynamic response
• Audible noise elimination
• VDD OVP (typical 28V) and VDD voltage clamp (30V Zener)
• Soft-drive circuit for optimized system EMI performance