DC/DC controller delivers 97% efficiency

20th February 2014
Nat Bowers

Replacing rectifying boost diodes with high efficiency N-channel MOSFETs, the LTC3784 high power two phase single output synchronous step-up DC/DC controller has been introduced by Linear Technology. It can produce a 24V output at 10A from a 12V input at up to 97% efficiency without a heat sink.

Operating from an input range of 4.5-60V during start-up, the LTC3784 maintains operation down to 2.3V after start-up and can regulate an output voltage as high as 60V. It can be configured for Burst Mode operation, where the device's 28µA quiescent current makes it suitable for “Always-on” automotive applications to extend battery run-time during standby mode while keeping the output voltage in regulation. It also features a powerful 1.2Ω onboard N-channel MOSFET gate drivers which can quickly slew large MOSFETs.

The LTC3784 enables easy paralleling of multiple devices for up to 12-phase operation for very high power applications, thanks to it's current mode architecture, clock output and phase modulation. Featuring adjustable cycle-by-cycle current limit, the LTC3784 has a phase-lockable switching frequency from 75-850kHz or a selectable fixed frequency from 50-900kHz. Additionally, the DC/DC controller can use a sense resistor or the voltage drop across the inductor for current sensing.

The LTC3784 allows the synchronous MOSFET to be kept on continuously for keep alive applications where the input voltage may exceed the regulated output voltage. This means that the that the output voltage follows the input voltage with minimal power loss. Furthermore, the LTC3784 has adjustable soft-start, a power good output and maintains ±1% reference voltage accuracy.

The LTC3784 is available in E, I H and MP grades in SSOP-28 and 4x5mm QFN-28 packages priced from $3.76 (USD) each in 1,000 unit quantities. The LTC3784E and LTC3784I operate over a temperature range from -40 to +125°C, while the LTC3784H is guaranteed to operate from a -40 to +150°C operating junction temperature. The LTC3784MP operates over a temperature range from -55 to +150°C.

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