ADVANCE INFORMATION for pre-production products; subject to change without notice.
The duty cycle of a buck converter operated in PWM mode is given as D=VOUT/VIN. The duty cycle increases as the input voltage comes close to the output voltage and the off-time gets smaller. When the minimum off-time of typically 30 ns is reached, TPS6281x-Q1 skips switching cycles while it approaches 100% mode. In 100% mode, it keeps the high-side switch on continuously. The high side switch stays turned on as long as the output voltage is below the target. In 100% mode, the low side switch is turned off. The maximum dropout voltage in 100% mode is the product of the on-resistance of the high side switch plus the series resistance of the inductor and the load current.