60V Synchronous Boost Controller Reduces Thermal Stress
During this year's Techno Frontier, Linear Technology Corporation announced the LTC3769, a synchronous step-up dc-dc controller that replaces the boost diode with a high-efficiency N-channel MOSFET, increasing efficiency and maximizing output current capability. This controller produces 24V at up to 5A output from a 12V input with up to 98% efficiency, making it suited for automotive, industrial and medical applications where a step-up dc-dc converter must have low heat dissipation in a small solution size.
The LTC3769 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. The low 28µA quiescent current extends the run time in battery-powered applications when in standby mode with the output voltage in regulation. 1.2 Ohm onboard N-channel MOSFET gate drivers are capable of slewing large MOSFET gates quickly, minimizing 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 50kHz to 900kHz or it can be synchronized to an external clock from 75kHz to 850kHz. Furthermore, this device has adjustable soft-start, a power good output signal and maintains ±1% reference voltage accuracy over a -40 to 125 degrees 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 degrees C for the extended and industrial grades, a high-temp automotive range of -40 to 150 degrees C and a military grade of -55 to 150 degrees C. The 1,000-piece price starts at $2.75 each.
