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Switching regulator targets automotive 'always-on' systems

Posted: 29 Feb 2016     Print Version  Bookmark and Share

Keywords:Linear Technology  regulator  industrial  automotive  oscillator 

Linear Technology Corp. has uncloaked a 65V input capable synchronous step-down switching regulator that can deliver up to 3.5A of continuous output current and peak loads of 5A to voltages as low as 0.81V. The LT8641 features a unique Silent Switcher architecture, which when combined with spread spectrum frequency modulation, cuts 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, indicated the company.

Synchronous rectification delivers efficiency as high as 94 per cent 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 company added.

The LT8641'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 optimise efficiency while avoiding critical noise sensitive frequency bands. The LT8641's 18-lead 3mm x 4mm QFN package and high switching frequency keep external inductors and capacitors small, providing a compact, thermally efficient footprint, Linear Tech stated.

LT8641 block diagram

Figure 1: LT8641 block diagram

The LT8641 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 10mVP-P. Special design techniques and a novel 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, continued the company. Other features include internal compensation, a power good flag, output soft-start/tracking and thermal shutdown.

An industrial temperature version of the LT8641EUDC, 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.





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