Demonstration circuit 1060 features two LT3508 step-down DC/DC switching converters. One circuit uses the LT3508EFE and the other circuit has the LT3508EUF. The LT3508 dual output step-down switching regulator has two internal power switches, a wide input voltage range, adjustable switching frequency synchronizable over the frequency range, programmable soft-start, tracking, power-good, and channel sequencing. The anti-phase switching reduces the input capacitor. The wide VIN range of the LT3508 allows step-down configurations with up to 36V input. The high power internal switches have current limit that allows for up to 1.4A output on each output.
The demonstration circuit has two circuits. The top is optimized for high efficiency, wide input range and maximum output current; the bottom is optimized for the size. The top circuit is rated for 3.3V at 1.4A and 5V at 1.4A output from a 6V–36V input using the FE package. The frequency is set to 700kHz to allow for the high VIN to VOUT ratio and provides high efficiency throughout the range. The bottom circuit generates 1.8V at 1A and 3.3V at 1A from a 5V to 16V DC input using the QFN package and shows off the compact size with 1.6MHz switching frequency.