Demonstration circuit DC2855A is a triple output synchronous step-up/dual step-down supply featuring the LTC 7818. The demonstration circuit is designed for two buck outputs 5V/10A, 3.3V/10A supplied by a boosted 10V output. Benefiting from this feature, the buck outputs are able to maintain regulation over a wide input voltage range of 4.5V to 36V which is suitable for automotive or other battery fed applications. Also, the demonstration circuit uses a drop-in layout whereas the main buck circuit components fit in an area of ¾” by 1½”, while the main boost circuit area is ¾” by 1¾”. The package style for the LTC7818 is a 40-pin exposed pad QFN.
The main features of the board include rail tracking (Buck channels only), an internal 5V linear regulator for bias, separated RUN pins for each output, a PGOOD signal (CH1 only), an overvoltage indicator for CH3 and a Mode selector that allow the converter to run in CCM, Pulseskipping or Burst Mode operation. Spread Spectrum Mode is availiable for EMI improvement. Synchronization to an external clock is also possible. The LTC7818 datasheet gives a complete description of these parts, operation and application information. The datasheet must be read in conjunction with this quick start guide for demo circuit 2855A.