Single-inductor, 60V input DC/DC controller

April 02, 2013 // By Graham Prophet
Linear Technology's LTC3863 is a high voltage inverting DC/DC controller that simplifies design by using a single inductor to produce a negative voltage from a positive input voltage. Most low to medium power inverters utilise a coupled inductor topology, or transformer which increases the circuit size and complexity.

The LTC3863 simplifies the design further with all of its interface signals being positive ground referenced. None of the LTC3863 pins are connected to a negative voltage allowing the output voltage to be limited only by the selection of external components.

The LTC3863, operating over a 3.5V to 60V input supply range, is designed to protect against high voltage transients, to operate continuously during automotive cold crank and cover a broad range of input sources and battery chemistries. This device helps increase the run-time in battery-powered applications with its low 70µA quiescent current in standby mode with the output enabled in Burst Mode operation. The LTC3863’s output voltage can be set from -0.4V to -150V or lower at up to 3A typical; making it suited to 12V or 24V automotive, heavy equipment, industrial control, robotic and telecom applications.

The LTC3863 drives an external P-channel MOSFET, operates with a selectable fixed frequency between 50kHz and 850kHz and is synchronisable to an external clock from 75kHz to 750kHz. Its current-mode architecture provides easy loop compensation, fast transient response, cycle-by-cycle over current protection and good line regulation. Output current sensing is accomplished by measuring the voltage drop across a sense resistor. Additional features include programmable soft start or tracking, overvoltage protection, overcurrent and short-circuit protection, a power good output signal and FMEA (failure mode and effects analysis) verified for adjacent pin opens and shorts. It occupies a 12-pin thermally enhanced MSOP or 3 x 4mm QFN package. LTC3863E and LTC3863I versions operate from a -40°C to 125°C junction temperature. LTC3863H grade is guaranteed to operate from a -40°C to 150°C operating junction temperature. LTC3863MP is guaranteed to operate from a -55°C to 150°C operating junction temperature. Pricing is from $2.06 (1,000). More;