Device identity and topology flexibility
The UCC3813DTR-0 is a BiCMOS current-mode PWM controller from Texas Instruments that handles Step-Up and Step-Up/Step-Down topologies — specifically Boost, Flyback, and Forward Converter configurations. A single output drives an external transistor switch, with a maximum duty cycle of 99% that allows the controller to run near continuous conduction in a boost stage without dropping out. The 46 kHz switching frequency is fixed by an internal oscillator; Frequency Control on the pinout lets the designer synchronise or trim the ramp, but there is no external clock-sync input.
The controller operates from a 6.9 V to 12 V Vcc rail — the undervoltage lockout thresholds are set internally for this band, so the bias supply must stay above 6.9 V for the chip to start switching.