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Synchronous boost controller reaches 97 percent efficiency, eliminates heat sink

September 28, 2010 | Christoph Hammerschmidt | 222901105
Synchronous boost controller reaches 97 percent efficiency, eliminates heat sink Linear Technology broadens its product spectrum with a two phase single output synchronous step-up DC/DC controller. The device replaces the usual boost diodes with high efficiency -channel MOSFETs, eliminating the heat sink normally required in medium to high power boost converters. Target markets include automotive audio, industrial and medical applications.

The LTC3787 can produce a 24V at 10A output from a 12V input. According to Linear, it reaches an efficiency of up to 97 percent under these operation conditions. The LTC3787's 135uA standby quiescent current when configured for Burst Mode operation makes it ideal for high power automotive audio amplifiers, as well as industrial and medical applications where a step-up DC/DC converter must deliver high power in a small solution size.

The LTC3787 operates from an input voltage ranging from 4.5V to 38V during start-up, maintains operation down to 2.5V after start-up and can regulate an output voltage as high as 60V. The 1.2Ohm onboard N-channel MOSFET gate drivers are capable of slewing large MOSFET gates quickly. The device's current mode architecture, clock output and phase modulation enables easy paralleling of multiple devices for up to 12 phase operation. The LTC3787 has a phase-lockable frequency from 75kHz to 850kHz or a selectable fixed frequency from 50kHz to 900kHz. In applications where the input voltage exceeds the regulated output voltage, the LTC3787 keeps the synchronous MOSFET on continuously so that the output voltage follows the input voltage with minimal power loss. In addition, this device features adjustable cycle-by-cycle current limit and can use a sense resistor or monitor the voltage drop across the inductor (DCR) for current sensing. Furthermore, the LTC3787 has adjustable soft-start, a power good output and maintains +1% reference voltage accuracy over an operating junction temperature range of -40°C to 125°C.

The LTC3787 is available in SSOP-28 and 4mm x 5mm QFN-28 packages. The 1,000-piece price starts at $4.12 each.

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