42V, 6A output step-down switcher runs at 95%

42V, 6A output step-down switcher runs at 95%

New Products |
LT8640S is a 6A, 42V input synchronous step-down switching regulator using Linear Technology’s (now Analog Devices) Silent Switcher 2 architecture to delivers 95% efficiency at 2 MHz, with very low EMI/EMC emissions.
By Graham Prophet


The device incorporates two internal input capacitors as well as internal BST and INTVCC capacitors to minimize the area of the “hot” loops. Combined with very well controlled switching edges and an internal construction with an integral ground plane and the use of copper pillars in lieu of bond wires, the LT8640S’s design significantly reduces EMI/EMC emissions. This improved EMI/EMC performance is not sensitive to board layout, simplifying design and reducing risk even when using two-layer PC boards. The LT8640S can easily pass the automotive CISPR 25, 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 LT8640S’s synchronous rectification delivers efficiency as high as 95% with a switching frequency of 2 MHz. Its 3.4V to 42V input voltage range is suitable for automotive and industrial applications. The internal high efficiency switches can deliver up to 6A of continuous output current and peak loads of 7A to voltages as low as 0.97V. The LT8640S’s Burst Mode operation requires only 2.5 µA of quiescent current, for applications such as automotive always-on systems. The LT8640S’s design maintains a minimum dropout voltage of 100 mV (at 1A) under all conditions, enabling it to excel in scenarios such as automotive cold-crank. A fast minimum on-time of 30 nsec enables 2 MHz constant frequency switching from a 16V input to a 1.5V output, enabling designers to optimize efficiency while avoiding critical noise-sensitive frequency bands. The LT8640S’s 24-lead, 4 x 4 mm LQFN package and high switching frequency keeps external inductors and capacitors small, providing a compact, thermally efficient footprint.


The LT8640S 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 10 mVP-P. For applications requiring the lowest noise operation, the LT8640S can be programmed to run in forced continuous mode over the entire load range. Its switching frequency is programmable and synchronizable from 200 kHz to 3 MHz. The device’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 LT8640SEV is packaged in a 4 x 4mm LQFN package. An industrial temperature version, the LT8640SIV, is tested and guaranteed to operate from a –40°C to 125°C operating junction temperature. Pricing starts at $4.65 (1,000).


Analog Devices/Linear Technology; www.linear.com/product/LT8640S



Linked Articles
eeNews Embedded