Demonstration Circuit DC2629A features the LTC3310S 10A, Low Voltage, Synchronous Step-Down Silent Switcher® 2 operating as a 2MHz 3.3V to 1.2V 10A buck regulator. The LTC3310S supports output voltages from 0.5V to VIN with operating frequencies from 500kHz up to 5MHz. The LTC3310S 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 VIN to low VOUT conversion at high frequency.
DC2629A is set up to run in Forced Continuous Mode with a 2MHz switching frequency but can be configured to Pulse Skip Mode and different switching frequencies. RT is connected to VIN which sets the MODE/SYNC pin as an input and allows the LTC3310S to sync from an external clock. Connecting the MODE/SYNC pin to VIN sets the mode to Forced Continuous Mode and connecting the MODE/SYNC pin to GND sets the mode to Pulse Skip 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 DC2629A 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 LTC3310S data sheet gives a complete description of the part, operation and application information. The data sheet must be read in conjunction with this demo. The LTC3310S is assembled in a 3mm x 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.