Step-down switcher offers very high efficiency, handles cold-crank

May 22, 2014 // By Christoph Hammerschmidt
The LT8620 from Linear Technology is a 2A, 65V input capable synchronous step-down switching regulator. Synchronous rectification delivers efficiency as high as 95% while Burst Mode operation keeps quiescent current under 2.5µA in no-load standby conditions. The chip's 3.4V to 65V input voltage range makes it ideal for automotive (single and dual battery) and industrial applications.

Its internal high efficiency switches deliver up to 2A of continuous output current to voltages as low as 0.97V. The LT8620's ultralow quiescent current makes it well suited for applications such as automotive “always-on” systems, which need to extend operating battery life. The LT8620’s unique design maintains a minimum dropout voltage of only 250mV at 1A under all conditions, enabling it to excel in scenarios such as automotive cold-crank.

The device’s fast minimum on-time of only 30ns enables 2MHz constant frequency switching from a 16V input to a 1.5V output, enabling designers to optimize efficiency while avoiding critical noise-sensitive frequency bands. The LT8620’s 24-lead 3mm x 5mm QFN or thermally enhanced MSOP-16E package and a high switching frequency keeps external inductors and capacitors small, providing a compact, thermally efficient footprint.

The LT8620 integrates internal top and bottom high efficiency power switches with the necessary boost diode, oscillator, control and logic circuitry integrated into a single die. Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping output ripple below 10mVPK-PK. Special design techniques and a new high speed process enable high efficiency over a wide input voltage range, and the LT8620’s current-mode topology enables fast transient response and excellent loop stability. Other features include internal compensation, a power good flag, output soft-start/tracking and thermal protection.

For more information, visit www.linear.com/product/LT8620