The LM557x and LM2557x line of SIMPLE SWITCHER buck regulators feature all of the functions necessary to implement an efficient, high-voltage buck regulator design using minimal external components. These regulators operate with an input voltage range up to 75 V and deliver up to 3 A of continuous output current. The patented emulated-current-mode architecture provides superior load transient response in low duty cycle applications that are not addressable by traditional current mode control. Operating frequency is adjustable from 50 kHz to 1 MHz, providing industry-leading dynamic range. To reduce EMI, a frequency synchronization pin allows multiple ICs from the series to self-synchronize or to synchronize to an external clock. These regulators guarantee robustness with cycle-by-cycle current limit, short-circuit protection, and thermal shut-down.