Linear's latest synchronous step-down Silent Switcher delivers 94% efficiency at 2MHz & ultralow EMI



The LT8641 3.5A, 65V input capable synchronous step-down switching regulator

Linear Technology announced the LT8641, a 3.5A, 65V input capable synchronous step-down switching regulator. A unique Silent Switcher architecture, combined with spread spectrum frequency modulation, reduces EMI/EMC emissions by more than 25dB even with switching frequencies in excess of 2MHz, enabling it to easily pass the automotive CISPR25 class 5 peak and average limits. Synchronous rectification delivers efficiency as high as 94% with a switching frequency of 2MHz. Its 3V to 65V input voltage range makes it ideal for single or dual cell automotive/transportation and industrial applications.

The LT8641's internal high efficiency switches deliver up to 3.5A of continuous output current and peak loads of 5A to voltages as low as 0.81V. The device's Burst Mode operation keeps quiescent current under 2.5µA in no load standby conditions, making it well suited for applications such as automotive "always-on" systems, which need to extend operating battery life.

The LT8641's unique design maintains a minimum dropout voltage of only 130mV at 1A under all conditions, enabling it to excel in scenarios such as automotive cold crank. Furthermore, a fast minimum on-time of only 35ns enables 2MHz constant frequency switching from a 24V input to a 3.3V output, equipping designers to optimize efficiency while avoiding critical noise sensitive frequency bands. The LT8641's 18­lead 3mm x 4mm QFN package and high switching frequency keep external inductors and capacitors small, providing a compact, thermally efficient footprint.

The LT8641 utilizes 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 10mVP-P. Special design techniques and a new high speed process enable high efficiency over a wide input voltage range, and the LT8641’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 shutdown.

The LT8641EUDC is packaged in a 3mm x 4mm QFN package. An industrial temperature version, the LT8641IUDC, is tested and guaranteed to operate from a -40°C to 125°C operating junction temperature. Pricing starts $4.35 each in 1,000-piece quantities and both versions are available from stock. 


Linear Technology