A buck switching regulator receives an input voltage and provides a
switching output voltage on a switch output node using a minimum on-time,
variable off-time feedback control loop. The buck switching regulator
includes an on-time control circuit for generating a first signal for
turning off the high-side switch at the expiration of a first on-time
duration or at the expiration of a maximum on-time. The first on-time
duration is at least a minimum on-time and is allowed to expand to a
maximum on-time when the feedback voltage remains less than a reference
voltage. The maximum on-time includes a first maximum on-time and a
second, extended maximum on-time. The second maximum on-time is applied
when a minimum off-time was used for the high-side switch during the
previous switching cycle. In another embodiment, the second maximum
on-time is applied only when the switching regulator is not being current
limited.