Step-down regulator maintains 400mV dropout voltage

Article By : EE Times India

The LT8609S’s synchronous rectification delivers efficiency as high as 93% with a switching frequency of 2MHz, according to Analog Devices.

A 42V input synchronous step-down switching regulator from Analog Devices features a unique Silent Switcher 2 architecture, which uses two internal input capacitors as well as an internal BST and INTVCC capacitors to minimise the area of the hot loops.

The LT8609S design reduces EMI/EMC emissions due to its controlled switching edges, its internal construction with an integral ground plane and the use of copper pillars in lieu of bond wires. The improved EMI/EMC performance is not sensitive to board layout, simplifying design and reducing risk even when using two-layer PC boards. The LT8609S passes 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 2.5µA of quiescent current, which is well suited for applications such as automotive always-on systems, needed to extend operating battery life.

The LT8609S’s design also maintains a minimum dropout voltage of only 400mV (at 1.5A) under all conditions, which is needed 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, optimising efficiency while avoiding critical noise-sensitive frequency bands.

The LT8609S 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. Its switching frequency is programmable and synchronisable 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.

The LT8609SEV is packaged in a 3mm x 3mm LQFN package. An industrial temperature version, the LT8609SIV, is tested and guaranteed to operate from a -40°C to 125°C operating junction temperature. Pricing starts at ₹186.99 ($2.75) each for 1,000-piece quantities and both versions are available from stock.

Aside from LT8609SEV, Analog Devices has also introduced a 4MHz synchronous dual output buck regulator and a half-duplex transceiver that can withstand up to ±40kV HBM.

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