Linear's 20V, synchronous 4-switch buck-boost LED driver with spread spectrum suits a variety of lighting applications



LT8391 synchronous buck-boost DC/DC LED controller

Linear Technology announced the LT8391, 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 makes it ideal for a wide variety of applications, including automotive, industrial and architectural lighting. Similarly, 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 of LED power.

Its buck-boost capability makes it well suited 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 is offered in either a 28-lead 4mm x 5mm QFN or thermally enhanced TSSOP to provide a very compact solution footprint.

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 proprietary peak-buck, peak-boost current mode control scheme allows adjustable and synchronizable 150kHz to 650kHz 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.

The LT8391EFE is available in 28-lead thermally enhanced TSSOP package, and the LT8391EUFD is offered in a 28-lead 4mm x 5mm QFN package. Industrial grade versions, the LT8391IFE and LT8391IUFD, are also available. Pricing starts at $4.65 each in 1,000-piece quantities. All versions are available from stock. For more information, visit

Summary of Features: LT8391
4-Switch Single Inductor Architecture Allows VIN Above, Below or Equal to VOUT
Synchronous Switching:
Up to 98% Efficiency
Proprietary Peak-Buck Peak-Boost Current Mode
Wide VIN Range: 4V to 60V
Wide VOUT Range: 0V to 60V (51V LED)
±3% LED Current Accuracy
2000:1 External & 128:1 Internal PWM Dimming
High Side PMOS PWM Switch Driver
Integrated Bootstrap Diodes
No Top MOSFET Refresh Noise in Buck or Boost
Adjustable & Synchronizable:
150kHz to 650kHz
Flicker-Free Spread Spectrum for Low EMI
Open & Short LED Protection with Fault Reporting
Available in 28-Lead TSSOP with Exposed Pad & 28-Lead QFN 4mm x 5mm Packages 

Linear Technology