The TPS61377 operates at a quasi-constant frequency pulse width modulation (PWM) in moderate-to-heavy load condition. Based on the VIN to VOUT ratio, a circuit predicts the required off-time of the switching cycle. At the beginning of each switching cycle, the low-side N-MOSFET switch is turned on, and the inductor current ramps up to a peak current that is determined by the output of the internal error amplifier. After the peak current is reached, the current comparator trips. It turns off the low-side N-MOSFET switch and the inductor current goes through the body diode of the high-side N-MOSFET in a dead-time duration. After the dead-time duration, the high-side N-MOSFET switch is turned on. Since the output voltage is higher than the input voltage, the inductor current decreases. The high-side switch is not turned off until the off-time is reached. After a short dead-time duration, the low-side switch turns on again and the switching cycle is repeated. At light load, the TPS61377 implements two operating modes, PFM mode and forced PWM mode, to meet different application requirements. The operating mode is set by the status of the MODE pin. When the MODE pin is logic high, the device operates in forced PWM mode. When the MODE pin is logic low, the device operates in PFM mode.