At higher input voltages the on time of the high-side switch becomes small. When the minimum is reached (see Electrical Characteristics), the switching may become erratic and/or the output voltage may fall out of regulation. To avoid this behavior, the LM53625/35-Q1 automatically reduces the switching frequency at input voltages above about 20 V (see Application Curves). In this way the device avoids the minimum on-time restriction and maintains regulation at abnormally high battery voltages. The SYNC input is ignored during frequency foldback at high input voltages. Frequency foldback patterns are different for the fixed 3.3-V and the 5-V output options. The fixed 3.3-V option has a deeper foldback pattern to accommodate the lower duty cycle. The adjustable option has a fold-back patterns is similar to that of the fixed 3.3-V option.