Regulator reduces EMI/EMC emissions by over 25dB

11th December 2014

Siobhan O'Gorman

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Datasheet

A 5A, 42V input capable synchronous step-down switching regulator has been introduced by Linear Technology. Featuring Silent Switcher architecture and providing spread spectrum frequency modulation, the LT8640 reduces EMI/EMC emissions by more than 25dB. This is possible even with switching frequencies greater than 2MHz, enabling the device to pass the automotive CISPR25, Class 5 peak limits.

Synchronous rectification delivers efficiency as high as 95%, with a switching frequency of 2MHz. The regulator has an input voltage range of 3.4-42V, making it suitable for automotive and industrial applications.

Offering a low quiescent current of 2.5µA in no-load standby conditions through Burst Mode operation, the LT8640 is suitable for automotive ‘always-on’ systems, which need to extend operating battery life. Allowing it to excel in conditions such as automotive cold-crank, the regulator’s design maintains a minimum dropout voltage of only 100mV at 1A under all conditions. 2MHz constant frequency switching from a 16V input to a 1.5V output is enabled by a fast minimum on-time of only 40ns, optimising efficiency while avoiding critical noise-sensitive frequency bands.

The LT8640, which integrates a boost diode, oscillator, control and logic circuitry into a single die, utilises internal top and bottom high efficiency power switches. While keeping output ripple below 10mV_pk-pk, low ripple Burst Mode operation maintains high efficiency at low output currents. Fast transient response and loop stability is enabled by the device’s current-mode topology. Internal compensation, a power good flag, output soft start/tracking and thermal protection are also provided with the regulator.

The device’s 20-lead 3x4mm QFN package combined with its high switching frequency allows for small external inductors and capacitors and, therefore, a compact, thermally efficient footprint.

The LT8640EUDC is available and priced at $4.35 each. Linear Technology also offers an industrial temperature version of the regulator. The LT8640IUDC, which is tested and guaranteed to operate from a junction temperature range of -40 to 125°C, is priced at $4.79 each. An automotive temperature version, the LT8640HUDC, is also available. This version is tested and guaranteed to operate from a junction temperature of -40 to 150°C and priced at $5.04 each. All versions are sold in 1,000 unit quantities.