The device provides the maximum duty cycle limit (D_MAX) / minimum off time to cover the non-ideal factors caused by resistive elements. D_MAX decides the minimum input supply voltage (V_SUPPLY(MIN)), which can achieve the target output voltage (V_LOAD) during CCM operation, but V_SUPPLY(MIN) , which can achieve the target output voltage during DCM operation, is not limited by D_MAX. V_SUPPLY(MIN), which can achieve the target output voltage during CCM operation, can be estimated as follows. See also Figure 7-17.

where

• I_SUPPLY(MAX) is the maximum input current at V_SUPPLY(MIN) .
• R_DCR is the DC resistance of the inductor.
• R_DS(ON) is the turn-on resistance of the MOSFET.

At very light load condition or when V_SUPPLY is close to V_OUT-REG, the device skips the low-side driver pulses if the required on-time is less than t_ON-MIN. This pulse skipping appears as a random behavior. If V_SUPPLY is further increased to the voltage higher than V_OUT-REG, the required on time becomes zero and eventually the device can start bypass operation, which turns on the high-side driver 100% when the VOUT pin voltage is greater than V_OVTH.