Automotive/industrial dc/dc step-down maintains efficiency at high conversion ratios

August 05, 2014 // By Graham Prophet
Intersil's highly efficient buck controller for high current designs, the 55V ISL78268, provides very high step-down efficiency for industrial and automotive applications

ISL78268 is a 55V synchronous buck controller with 3A integrated high side and low side drivers. Positioned as the most versatile high voltage buck solution available, the ISL78268 buck controller provides very high step-down efficiency for a wide variety of load currents from under 5 to over 25A, enabling it to support virtually every 12, 24, or 48V high current buck requirement for automotive and industrial applications.

For heavy load applications, designers often have to balance power conversion efficiency against size and noise constraints. This requires making trade-offs among component selection, switching frequency, and output ripple and often requires the power stage to be tailored to the load in question. The ISL78268 buck solution was designed specifically to be flexible so that it can be used regardless of the optimisation balance.

The ISL78268 buck controller enables conversion from high primary rails (typically 12, 24 or 48V) to lower secondary rails (typically 3.3, 5.0 or 12V). It fully integrates both a peak current mode synchronous PWM controller and a dedicated constant current control loop as well as high-side and low-side FET drivers that have adaptive dead time control. The device's tolerance of 55V inputs makes it suitable for automotive applications, including support for the 12V clamped load-dump specifications and new 48V power system being adopted by European OEMs. The integrated 3A driver allows the controller to sharply switch small power FETs or parallel combinations of large FETs while minimising dead time to reduce switching losses, improve efficiency and reduce excess heat dissipation. This allows a single buck controller to be used across a wide variety of load requirements.

The part: supports 5-25A loads and can be used in a two-phase, current sharing configuration to support loads up to 50A; has 55V input tolerance (60V abs max), has integrated 3A FET drivers and PWM controller for cycle-by-cycle peak current limiting, provides average current limiting to extend battery life in battery charging applications