UC3846N

The UC3846N is a member of the UC1846/7 family of current mode PWM controllers from Texas Instruments. Designed for dual-ended power converter topologies, it integrates a differential current sense amplifier, an error amplifier, an oscillator with synchronization capability, and dual totem-pole output stages. The current mode control architecture provides improved line regulation, enhanced load response, and a simpler control loop design compared to voltage mode control. The device is optimized for push-pull, half-bridge, and bridge converter applications where automatic symmetry correction and pulse-by-pulse current limiting are critical for reliable operation.

The UC3846N operates using current mode control where the output inductor current is sensed and used as the feedback variable. The oscillator generates a clock signal that sets the switching frequency (up to 500 kHz). The error amplifier compares a scaled version of the output voltage with the internal 5.1 V reference, producing a control voltage. The current sense amplifier measures the inductor current through a differential input. The PWM comparator compares the current sense signal against the error amplifier output to determine the pulse width. Dual totem-pole outputs alternate based on a flip-flop, driving external power switches in push-pull or bridge configurations. Built-in UVLO ensures the device only operates when the supply voltage exceeds 7.7 V.

• Push-pull DC-DC converters for telecom power supplies
• Half-bridge converters for industrial power systems
• Battery chargers with current limiting requirements
• Modular power supply systems requiring parallel operation
• Offline flyback converters with current mode control