Quad output 42V buck regulator operates from 3V

Quad output 42V buck regulator operates from 3V

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By Nick Flaherty

The ‘Powered by Linear’ LT8603 combines a boost controller with two high voltage 2.5A and 1.5A synchronous step-down channels and a lower voltage 1.8A synchronous step-down channel to provide four independent outputs.

The regulator can be configured with the boost controller to supply the input of the buck converters, enabling it to deliver three regulated outputs. This is the case even when the input falls significantly below the regulated output voltages, such as in automotive cold crank or start-stop scenarios when the battery voltage can drop as low as 3V. Alternatively, the boost controller can be driven from one of the step-down outputs,  providing four precisely regulated outputs with a very compact solution footprint.

The LT8603’s triple buck synchronous rectification topology delivers up to 93% efficiency while Burst Mode operation keeps quiescent current under 28µA (high voltage channels active) in no-load standby conditions, ideal for always-on systems. For noise-sensitive applications, the regulator has a low EMI design that meets the CISPR 25, Class 5 EMI requirements even when switching at 2MHz and the switching frequency can be programmed from 250kHz to 2.2MHz and is synchronizable throughout this range.

The 85ns (max) minimum on-time and cascading topology enables 16V IN to 0.8V OUT step-down conversions while switching at 2MHz, enabling designers to avoid critical noise-sensitive frequency bands such as AM radio. The 3V to 42V input voltage range is aimed at automotive applications that must regulate through cold crank and stop-start scenarios with minimum input voltages as low as 3V and load dump transients in excess of 40V. 

Programmable power-on reset and power good indicators for each channel ensure overall system reliability.

The LT8603 is available in a thermally enhanced 40-lead 6mm x 6mm QFN package. Two temperature grades are available, with operation from –40°C to 125°C (junction) for the extended E- and industrial I-grades. All versions are available from stock from $5.35 in volume.


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