Step-Down Controllers Provide 75V Input Range

With an input-voltage range up to 75V, the LM5085, LM25085, LM5088, and LM25088 buck controllers can regulate output voltages as low as 1.2V at load currents in excess of 5A. Each offers a programmable switching frequency up to 1 MHz using a single resistor. The LM5085 and LM5088 operate from input voltages up to 75V and the LM25085 and LM25088 have a maximum input voltage of 42V. Available in 16-pin TSSOPs, the LM5088 and LM25088 N-channel MOSFET controllers feature an emulated current-mode, PWM control topology to regulate output voltages as low as 1.2V when operating from high input voltages. They employ a unique frequency dithering function that varies the switching frequency by ±5% around the nominal switching frequency, reducing EMI peak amplitude by 10 dB or more in typical applications. Synchronization to an external clock further controls EMI. Both devices can operate as a slave to an external master supply for applications requiring multiple supply rails that track each other during the start-up and power-down. Options include programmable cycle-by-cycle current limiting and a hiccup mode. Prices range from $0.85 to $1.60 each/1,000. NATIONAL SEMICONDUCTOR CORP., Santa Clara, CA. (800) 272-9959.