60V, synchronous 4-switch buck-boost spread spectrum LED driver

April 07, 2016 // By Graham Prophet
LT8391 is a synchronous buck-boost DC/DC LED controller that regulates LED current from input voltages above, below and equal to the output voltage. Its 4V to 60V input voltage range suits it for a wide variety of applications, including automotive, industrial and architectural lighting.

Its output voltage can be set from 0V to 60V, enabling it to drive a wide range of LEDs in a single string. Its internal 4-switch buck-boost controller, combined with four external N-channel MOSFETs, can deliver from 10W to over 100W. Its buck-boost capability suits it for applications such as automotive, where the input voltage can vary dramatically during stop/start, cold crank and load dump scenarios. Transitions between buck, pass-through and boost operating modes are seamless, offering a well-regulated output in spite of wide variations of supply

voltage. The LT8391 provides both internal (128:1) and external (2,000:1) LED current PWM dimming using an external high side PMOS switch. It comes in either a 28-lead 4 x 5 mm QFN or thermally enhanced TSSOP.


The LT8391 uses four external N-channel MOSFETs to deliver up to 100W of continuous LED power with efficiencies up to 98%. LED current accuracy of ±3% ensures constant lighting. The peak-buck, peak-boost current mode control scheme allows adjustable and synchronisable 150 kHz to 650 kHz fixed frequency operation or internal spread spectrum operation for low EMI. Additional features include integrated bootstrap diodes and open and short LED protection with fault reporting.


Pricing starts at $4.65 (1,000)


Linear Technology; www.linear.com/product/LT8391