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42V, 4A Synchronous Step-Down Silent Switcher Needs Only 2.5µA of Quiescent Current

The LT8614 is a step-down regulator featuring Silent Switcher architecture that is designed to minimize EMI/EMC emissions while delivering high efficiency at frequencies up to 3MHz. Assembled in a 3mm × 4mm QFN, the monolithic construction with integrated power switches and inclusion of all necessary circuitry yields a solution with a minimal PCB footprint. An ultralow 2.5µA quiescent current - with the output in full regulation - enables applications requiring highest efficiency at very small load currents. Its 3.4V to 42V input voltage range makes it ideal for medical, automotive and industrial applications.

In conjunction with Arrow Electronics Ltd.

The LT8614 from Linear Technology is a 4A, 42V input capable synchronous step-down switching regulator with a unique Silent Switcher architecture that reduces EMI/EMC emissions by more than 20dB, well below the CISPR 25 Class 5 limit.

Even with switching frequencies in excess of 2MHz, synchronous rectification delivers efficiency as high as 96% while Burst Mode operation keeps quiescent current under 2.5µA in no-load standby conditions. The 3.4V to 42V input voltage range of this device makes it ideal for medical, 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 well suited for applications such as automotive "always-on" systems, which need to extend operating battery life. The LT8614's unique design maintains a minimum dropout voltage of only 200mV at 1A under all conditions, enabling it to excel in scenarios such as automotive cold-crank.

Furthermore, a fast minimum on-time of only 30ns enables 2MHz constant frequency switching from a 16V input to a 1.0V output, enabling designers to optimize efficiency while avoiding critical noise-sensitive frequency bands. The LT8614's 20-lead 3mm x 4mm QFN package and high switching frequency keeps external inductors and capacitors small, providing a compact, thermally efficient footprint.

The LT8614 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 voltage ripple below 10mVPK-PK at any load, from zero to full current.

Special 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. Operation is safe in overload even with a saturated inductor.

Essential features are included and easy to use: An opendrain PG pin signals when the output is in regulation. The SYNC pin allows clock synchronization and choice of Burst Mode operation or pulse-skipping mode. Soft-start and tracking functionality is accessed via the TR/SS pin. An accurate enable threshold can be set using the EN/UV pin and a resistor at the RT pin programs switch frequency.

The LT8614EUDC is packaged in a 3mm x 4mm QFN package and is priced starting at $4.25 each. An industrial temperature version, the LT8614IUDC, is tested and guaranteed to operate from a -40°C to 125°C operating junction temperature and is priced starting at $4.68 each.

An automotive temperature version, the LT8614HUDC, is tested and guaranteed to operate from a -40°C to 150°C operating junction temperature and is priced starting at $4.93 each. All pricing is for 1,000-piece quantities and all versions are available from stock.

For more information, visit

Linear Technology (UK) Limited
Tel: +44 (0)1628 477066

Web site:

Linear Technology (UK) Limited

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