Automotive PWM controller in an 8-SOIC footprint
The Texas Instruments UCC28C40QDRQ1 is a BiCMOS low-power current-mode PWM controller in the 8-SOIC package, qualified to AEC-Q100 Grade 1 for automotive applications. It operates from a 6.6V to 18V supply rail and switches at 53 kHz with a maximum duty cycle of 96%.
What the 53 kHz switching frequency means for your power stage
At 53 kHz, the switching period is about 18.9 µs. This is a moderate frequency that keeps switching losses low in the external MOSFET while still allowing a reasonably small magnetic component — a flyback transformer or buck inductor wound on a ferrite core in the 10–20 µH range works without excessive copper loss. The 96% duty cycle ceiling means the controller can stay on for nearly the entire period, useful in a buck converter with a high step-down ratio or a flyback running near the boundary of continuous conduction. The part supports both buck and flyback topologies, with the output configured as a single PWM signal driving an external transistor. Synchronous rectification is built in, so the controller can drive a second MOSFET on the secondary side for better efficiency in low-voltage outputs.
Temperature grade and the automotive thermal envelope
The 8-SOIC package's thermal resistance (junction-to-ambient around 120°C/W in still air) means the die temperature stays within the 150°C absolute maximum as long as the power dissipation is kept under about 200 mW, which is easy for a controller drawing a few mA.
Control features and overcurrent protection
The controller includes cycle-by-cycle overcurrent limiting and a ramp compensation circuit. The overcurrent sense pin monitors the primary-side current through an external sense resistor; when the threshold is exceeded, the PWM pulse terminates immediately. The ramp compensation stabilises the inner current loop at duty cycles above 50%, preventing subharmonic oscillation in continuous-conduction-mode flyback or boost converters.