LT8391 Synchronous Buck-Boost LED Controllers Analog Devices Inc. LT8391 Controllers are 4-switch synchronous, buck-boost LED controllers. The controllers regulate output voltage, input, or output current from an input voltage above, below, or equal to the output voltage. The peak-buck/peak-boost current mode control scheme enables adjustable and synchronizable 150kHz to 650kHz fixed-frequency operation. The control scheme also allows internal ±15% triangle spread spectrum frequency modulation for low EMI.