42V, 2A/3A Peak (IOUT), Synchronous Step-Down Silent Switcher® 2 Delivers 93% Efficiency at 2MHz & Ultralow EMI/EMC Emissions

Analog Devices, Inc., which recently acquired Linear Technology Corporation, announces the LT8609S, a 2A (3A Peak), 42V input synchronous step-down switching regulator. Its unique 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. The LT8609S design dramatically reduces EMI/EMC emissions due to very well controlled switching edges, it’s internal construction with an integral ground plane and the use of copper pillars in lieu of bond wires. This improved EMI/EMC performance is not sensitive to board layout, simplifying design and reducing risk even when using two-layer PC boards. The LT8609S easily pass the automotive CISPR 25, Class 5 peak EMI limits with a 2MHz switching frequency over its entire load range. Spread spectrum frequency modulation is available to lower EMI/EMC levels further.

The LT8609S’s synchronous rectification delivers efficiency as high as 93% with a switching frequency of 2MHz. Its 3.0V to 42V input voltage range is ideal for automotive and industrial applications. The internal high efficiency switches deliver up to 2A of continuous output current and peak loads of 3A to voltages as low as 0.774V. The LT8609S’s Burst Mode® operation offers only 2.5µA of quiescent current, well suited for applications such as automotive always-on systems, needed to extend operating battery life. The LT8609S’s unique design maintains a minimum dropout voltage of only 400mV (at 1.5A) under all conditions, enabling it to excel in scenarios such as automotive cold crank. Furthermore, a fast minimum on-time of only 45ns enables 2MHz constant frequency, switching from a 16V input to a 1.5V output, optimizing efficiency while avoiding critical noise-sensitive frequency bands. The LT8609S’s 16-lead, 3mm x 3mm LQFN package and high switching frequency, which keeps the external inductor and capacitors small, providing a compact, thermally efficient footprint.

The LT8609S 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 ripple below 10mVP-P. Its switching frequency is programmable and synchronizable from 200kHz to 2.2MHz. Special design techniques and a new high speed process enable high efficiency over a wide input voltage range, and the LT8609S’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.