LM34917A,pdf datasheet (Regula

The LM34917A Step-Down Switching Regulator features all
the functions needed to implement a low cost, efficient, buck
bias regulator capable of supplying at least 1.25A to the load.
To reduce excessive switch current due to the possibility of a
saturating inductor the valley current limit threshold changes
with input and output voltages, and the on-time is reduced
when current limit is detected. This buck regulator contains
an N-Channel Buck Switch, and is available in the 12 pin micro
SMD package. The constant on-time feedback regulation
scheme requires no loop compensation, results in fast load
transient response, and simplifies circuit implementation. The
operating frequency remains constant with line and load variations
due to the inverse relationship between the input voltage
and the on-time. The valley current limit results in a
smooth transition from constant voltage to constant current
mode when current limit is detected, reducing the frequency
and output voltage, without the use of foldback. Additional
features include: VCC under-voltage lock-out, input over-voltage
shutdown, thermal shutdown, gate drive under-voltage
lock-out, and maximum duty cycle limit.