|National Semiconductor's LM34919 step down switching regulator features all of the functions needed to implement a low cost, efficient, buck bias regulator capable of supplying 0.6A to the load. This buck regulator contains an N-channel buck switch and is available in a micro SMD package. The constant on-time feedback regulation scheme requires no loop compensation, resulting in a fast load transient response and simplifying 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 the current limit is detected, reducing the frequency and output voltage without the use of foldback. Additional features include VCC under-voltage lockout, thermal shutdown, gate drive under-voltage lockout, and maximum duty cycle limiter.