LTC3311S

Demonstration Circuit 3018A features the LTC3311S 12.5A, low voltage, synchronous step-down Silent Switcher^™ 2 operating as a 2MHz 3.3V to 1.2V 12.5A buck regulator. The LTC3311S supports output voltages from 0.5V to V_IN with operating frequencies from 500kHz up to 5MHz. The LTC3311S is a compact, ultralow emission, high efficiency, and high speed synchronous monolithic step-down switching regulator. The integrated bypass capacitors optimize all the fast current loops and make it easier to minimize EMI/EMC emissions by reducing layout sensitivity. Fast minimum on-time of 35ns enables high V_IN to low V_OUT conversion at high frequency.

DC3018A is set up to run in forced continuous mode with a 2MHz switching frequency but can be configured to pulse skip mode or different switching frequencies. RT is connected to V_IN which sets the MODE/SYNC pin as an input and allows the LTC3311S to sync from an external clock. Connecting the MODE/SYNC pin to V_IN sets the mode to pulse skip mode and connecting the MODE/SYNC pin to GND sets the mode to forced continuous mode. The Efficiency vs Load graph shows the efficiency and the power loss of the circuit with a 3.3V input in forced continuous mode operation.

The DC3018A also has an EMI filter to reduce conducted EMI. This EMI filter can be included by applying the input voltage at the VIN EMI terminal. The EMI performance of the board is shown in the EMI Test Results section. The red lines in the EMI performance graphs illustrate the CISPR25 Class 5 peak limits for the conducted and radiated emission tests.

The LTC3311S data sheet gives a complete description of the part, operation and application information. The data sheet must be read in conjunction with the demo manual. The LTC3311S is assembled in a 3mm × 3mm LQFN package with exposed pads for low thermal resistance. The layout recommendations for low EMI operation and maximum thermal performance are available in the data sheet section Low EMI PCB Layout.