60V synchronous boost controller reaches 98% efficiency

July 24, 2014 // By Graham Prophet
LTC3769 is a synchronous step-up DC/DC controller that replaces the boost diode with a high efficiency N-channel MOSFET, increasing efficiency and maximising output current capability.

This controller produces 24V at up to 5A (120W) output from a 12V input with up to 98% efficiency, suiting it for automotive, industrial and medical applications where a step-up DC/DC converter must have low heat dissipation in a small solution size.

The device operates over an input voltage range of 4.5V to 60V during start-up, maintains operation down to 2.3VIN after start-up and can regulate an output as high as 60V. Its 28 µA quiescent current extends the run time in battery-powered applications when in standby mode with the output voltage in regulation. 1.2-Ω onboard N-channel MOSFET gate drivers are capable of slewing large MOSFET gates quickly, minimising transition losses and enabling up to 10A output current.

The LTC3769 has adjustable cycle-by-cycle current limit protection and uses either a sense resistor or monitors the voltage drop across the inductor (DCR) for current sensing. In applications where the input voltage may exceed the regulated output voltage, the LTC3769 keeps the synchronous MOSFET on continuously so that the output voltage follows the input voltage with minimal power loss. The LTC3769's current-mode architecture enables a selectable frequency from 50 kHz to 900 kHz or it can be synchronised to an external clock from 75 kHz to 850 kHz. It has adjustable soft-start, a power-good output signal and maintains ±1% reference voltage accuracy over a -40°C to 125°C operating temperature range.

The LTC3769 is available in 20-lead TSSOP and 24-pin 4mm x 4mm QFN packages. Four temperature grades are available, with operation from -40 to 125°C for the extended and industrial grades, a high temp automotive range of -40°C to 150°C and a military grade of -55°C to 150°C. Pricing starts at $2.75 (1000).

Linear Technology; www.linear.com/product/LTC3769