N-Channel MOSFETs Push Synchronous Boost Controller’s Efficiency To 97%
By replacing rectifying boost diodes with N-channel MOSFETs, the LTC3784 two-phase, single-output, synchronous step-up dc-dc controller can produce a 24-V output at 10 A from a 12-V input at up to 97% efficiency without a heatsink. Linear Technology’s controller operates from an input voltage ranging from 4.5 to 60 V during startup, and maintains operation down to 2.3 VIN after startup. It can regulate an output voltage as high as 60 V. In burst-mode operation, the device’s 28-µA quiescent current suits it for “always-on” automotive applications to extend battery run time during standby mode while keeping output voltage in regulation. The 1.2-Ω onboard N-channel MOSFET gate drivers can quickly slew large MOSFETs. A current-mode architecture, clock output, and phase modulation facilitate paralleling of multiple devices for up to 12-phase operation in high-power applications. Phase-lockable switching frequency ranges from 75 to 850 kHz; selectable fixed frequency ranges from 50 to 900 kHz. Other features include RSENSE or inductor DCR current sensing, and current-mode control. The LTC3784 comes in SSOP-28 and 4- by 5-mm QFN-28 packages.