The BQ24133 employs a 1.6-MHz constant frequency step-down switching regulator. The fixed-frequency oscillator keeps tight control of the switching frequency under all conditions of input voltage, battery voltage, charge current, and temperature, simplifying output filter design and keeping it out of the audible noise region.

A type III compensation network allows using ceramic capacitors at the output of the converter. An internal saw-tooth ramp is compared to the internal error control signal to vary the duty cycle of the converter. The ramp height is proportional to the AVCC voltage to cancel out any loop gain variation due to a change in input voltage, and simplifies the loop compensation. Internal gate drive logic allows achieving 97% duty cycle before pulse skipping starts.