The LM25574 switching regulator features all of the functions necessary to implement an efficient high voltage buck regulator using a minimum of external components. This easy to use regulator integrates a 42-V N-channel buck switch with an output current capability of 0.5 Amps. The regulator control method is based on current mode control using an emulated current ramp. Peak current mode control provides inherent line voltage feed-forward, cycle-by-cycle current limiting, and ease of loop compensation. The use of an emulated control ramp reduces noise sensitivity of the pulse-width modulation circuit, allowing reliable processing of very small duty cycles necessary in high input voltage applications. The operating frequency is user programmable from 50 kHz to 1 MHz. An oscillator synchronization pin allows multiple LM25574 regulators to self synchronize or be synchronized to an external clock. The output voltage can be set as low as 1.225 V. Fault protection features include, current limiting, thermal shutdown and remote shutdown capability. The device is available in the TSSOP-16 package.

The functional block diagram and typical application of the LM25574 are shown in Section 6.2. The LM25574 can be applied in numerous applications to efficiently step-down a high, unregulated input voltage. The device is an excellent choice for telecom, industrial and automotive power bus voltage ranges.