Switching regulator delivers 93% efficiency at 2MHz

20th April 2016
Joe Bush

The new LT8608 from Linear Technology is a 1.5A, 42V input synchronous step-down switching regulator with synchronous rectification topology that delivers 93% efficiency while switching at 2MHz. This enables designers to avoid critical noise sensitive frequency bands, such as AM radio, while using a very compact solution footprint. Burst Mode operation keeps quiescent current under 2.5µA in no-load standby conditions making it well suited for always-on systems.

Its 3.0V to 42V input voltage range makes it well suited for automotive applications which must regulate through cold-crank and stop-start scenarios with minimum input voltages as low as 3.0V and load dump transients in excess of 40V. Its internal 2A switches can deliver up to 1.5A of continuous output current. The LT8608 maintains a minimum drop-out voltage of only 200mV (@500mA) under all conditions, enabling it to excel in scenarios such as automotive cold-crank.

Spread spectrum frequency modulation and special design techniques offer low EMI operation to minimise noise concerns in automotive and industrial environments. Furthermore, a fast minimum on-time of only 45ns enables 2MHz constant frequency switching from a 16V input to a 1.5V output. The LT8608’s ten lead thermally enhanced MSOP package and high switching frequency keeps external inductors and capacitors small - providing a compact, thermally efficient footprint.

The LT8608 utilises 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. The design techniques and a new high speed process enable high efficiency over a wide input voltage range, and the LT8608’s current mode topology enables fast transient response and loop stability. Other features include internal compensation, a power good flag, output soft-start/tracking and thermal protection.

The LT8608EMSE is packaged in a thermally enhanced MSOP-10 package. An industrial temperature version, the LT8608IMSE, is tested and guaranteed to operate from a -40°C to 125°C operating junction temperature.

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