42V DC/DC combines high efficiency with low quiescent current

March 09, 2016 // By Graham Prophet
LT8601 is a 42V input capable, high efficiency triple output synchronous monolithic step-down switching regulator. Its triple channel design combines two high voltage 2.5A and 1.5A channels with a lower voltage 1.8A channel to deliver three independent voltage outputs as low as 0.8V.

Its synchronous rectification topology delivers up to 93% efficiency while Burst Mode operation keeps quiescent current under 30 µA (all channels) in no-load standby conditions, for always-on systems. For noise sensitive applications, the LT8601 can employ its pulse-skipping mode to minimise switching noise and it meets the CISPR25, Class 5 EMI requirements. Switching frequency can be programmed from 250 kHz to 2.2 MHz and is synchronisable throughout this range.


The converter’s 60 nsec minimum on-time enables 16 V IN to 0.8 V OUT step-down conversions while switching at 2 MHz, enabling designers to avoid critical noise-sensitive frequency bands, such as AM radio, while using a very compact solution footprint. Its 3V to 42V input voltage range is suitable for automotive applications which 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. Each channel of the LT8601 maintains a minimum dropout voltage of 250 mV at 1A under all conditions, for scenarios such as automotive cold-crank. There are programmable power-on reset and power good indicators for each channel. The LT8601’s 40-lead thermally enhanced 6 x 6 mm QFN package and high switching frequency keeps external inductors and capacitors small, providing a compact, thermally efficient footprint.


The LT8601 uses triple internal top and bottom high efficiency power switches with the necessary boost diodes, oscillator, control and logic circuitry integrated into a single die. Channel 1 switches 180° out-of-phase with channels 2 and 3 to reduce output ripple. Each channel has a separate input for added design flexibility, but most applications will run the low voltage channel directly from one of the two high voltage channels to offer a very simple, high frequency triple output design. Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping output ripple below 15 mVP-P. Efficiency is maintained over a wide input voltage range, and the LT8601’s