42V, 4A synchronous step-down cuts power-rail noise levels

October 22, 2013 // By Graham Prophet
Linear Technology's LT8614 is a 4A, 42V-input-capable synchronous step-down switching regulator with a quiescent current demand of 2.5 µA. Its Silent Switcher architecture reduces EMI/EMC emissions by more than 20 dB, well below the CISPR 25 Class 5 limit.

Even with switching frequencies in excess of 2 MHz, synchronous rectification delivers efficiency as high as 96% while Burst Mode operation keeps quiescent current under 2.5µA in no-load standby conditions. Its 3.4V to 42V input voltage range suits it for for automotive and industrial applications.

The LT8614’s internal high efficiency switches can deliver up to 4A of continuous output current to voltages as low as 0.97V. Its Burst Mode operation provides ultralow quiescent current, making it appropriate for applications such as automotive “always-on” systems, which need to extend operating battery life. The LT8614’s design maintains a minimum dropout voltage of 200mV at 1A under all conditions, including automotive cold-crank. Fast minimum on-time of 30 nsec enables 2 MHz constant frequency switching from a 16V input to a 1.0V output, enabling you to optimise efficiency while avoiding critical noise-sensitive frequency bands. Its 20-lead 3 x 4mm QFN package and high switching frequency keeps external inductors and capacitors small, providing a compact, thermally efficient footprint.

The LT8614 uses 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 10 mVpk-pk. Design techniques and a new high speed process enable high efficiency over a wide input voltage range, and the LT8614’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.

The LT8614EUDC is priced starting at $4.25 (1000). An industrial temperature version, the LT8614IUDC, operates from a -40°C to 125°C operating junction temperature is $4.68 (1000). An automotive temperature version, the LT8614HUDC, operates from a -40°C to 150°C operating junction temperature and is $4.93 (1000).

Linear Technology; www.linear.com/product/LT8614