Using four external N-channel MOSFETs, the LT8391 synchronous buck-boost DC/DC controller from Linear Technology drives a wide range of LEDs in a single string. It regulates LED current from input voltages above, below, or equal to the output voltage. The part’s input voltage range of 4 V to 60 V and output voltage range of 0 V to 60 V make it well-suited for automotive, industrial, and architectural lighting.
The LT8391’s internal four-switch buck-boost controller, along with the four external MOSFETs, delivers 10 W to over 100 W of continuous LED power with efficiencies of up to 98%. LED current accuracy of ±3% ensures constant lighting. The device also provides both internal (128:1) and external (2000:1) LED current PWM dimming using an external high-side PMOS switch.
The peak-buck, peak-boost current-mode control employed by the LT8391 allows adjustable and synchronizable fixed-frequency operation from 150 kHz to 650 kHz. To improve EMI performance, internal ±15% triangle spread-spectrum frequency modulation can be enabled.