Demonstration circuit 3021A shows the LTC3310S-1 10A, 1V fixed output, synchronous step-down Silent Switcher®2 operating as a 2MHz 3.3V to 1.0V 10A buck regulator. The LTC3310S-1 supports operating frequencies from 500kHz up to 5MHz. The LTC3310S-1 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. The LTC3310S-1 has Active Voltage Positioning (AVP) where the output voltage is dependent on load current. At light loads, the output voltage is regulated above the nominal value. At full load, the output voltage is regulated below the nominal value. The DC load regulation is adjusted to improve transient performance and reduce output capacitor requirements.
DC3021A is set up to run in forced continuous mode with a 2MHz switching frequency but can be configured to pulse-skipping mode and different switching frequencies. RT is connected to VIN which sets the MODE/SYNC pin as an input and allows the LTC3310S-1 to sync from an external clock. Connecting the MODE/SYNC pin to VIN sets the mode to pulse-skipping mode and connecting the MODE/SYNC pin to GND sets the mode to forced continuous mode.
The DC3021A 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 of the demo manual. The red lines in the EMI performance graphs illustrate the CISPR25 Class 5 peak limits for the conducted and radiated emission tests.
The LTC3310S/LTC3310S-1 data sheet gives a complete description of the part, operation and application information. The data sheet must be read in conjunction with the DC3021A demo manual. The LTC3310S-1 is assembled in a 3mm × 3mm LQFN package with exposed pad 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.