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65 V, 8 A synchronous step-down regulator delivers 94% efficiency at 2 MHz

The LT8645S is an 8-A, 65-V input-capable synchronous step-down switching regulator. It features the Silent Switcher 2 architecture, uses two internal input capacitors as well as internal BST and INTVCC capacitors to minimize the area of the hot loops. Combined with controlled switching edges and internal construction with an integral ground plane and the use of copper pillars in lieu of bond wires, the step-down regulator reduces EMI/EMC emissions. The improved EMI/EMC performance is not sensitive to board layout, simplifies design and reduces risk even when using two layer PC boards. The LT8645S can pass the automotive CISPR25, Class 5 peak EMI limits with a 2 MHz switching frequency over its entire load range. Spread spectrum frequency modulation is also available to lower EMI/EMC levels further.

 

The regulator’s synchronous rectification delivers efficiency as high as 94% and the input voltage range targets dual cell transportation, and 48 V automotive and industrial applications. The internal high efficiency switches can deliver up to 8 A continuous output current to voltages as low as 0.97 V. The regulator’s Burst Mode operation offers 2.5 µA of quiescent current, suitable for automotive/ transportation always-on systems, which need to extend operating battery life.

The regulator maintains a minimum dropout voltage of only 60 mV (at1 A) under all conditions, enabling it to excel in scenarios such as automotive cold-crank. Furthermore, a fast minimum on-time of only 40 ns enables 2 MHz constant frequency switching from a 24-V input to a 2.0 V output, enabling designers to optimize efficiency while avoiding critical noise-sensitive frequency bands. The 32-lead, 4 x 6 mm LQFN package and high switching frequency keeps external inductors and capacitors small.

The LT8645S 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 mVP-P. For applications requiring the lowest noise operation, the LT8645S can be programmed to run in pulse-skipping mode. Its switching frequency is programmable and synchronizable from 200 kHz to 2.2 MHz. For more information on the Analog Devices/Linear Technology: www.linear.com/product/LT8645S

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