Overview

Product Details

Demonstration Circuit 3113A features the LTC3311-1, fixed 1V, 12.5A synchronous step-down Silent Switcher® operating as a 2MHz, 3V to 3.6V input, 1V/12.5A output buck regulator. The LTC3311-1 supports fixed 1V output voltage with operating frequencies from 500kHz up to 5MHz. The LTC3311-1 is a compact, ultralow emission, high efficiency, and high speed synchronous monolithic step-down switching regulator. The LTC3311-1 has Active Voltage Positioning (AVP) where the output voltage is dependent on load current. At light load, 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 required output capacitance.

DC3113A is set up to run in forced continuous mode with a 2MHz switching frequency but can be configured to run at different switching frequencies, or in pulse-skipping mode. The LTC3311-1 oscillator can also synchronize to an external clock using MODE/SYNC turret, with the DC3113A default setup. Figure 7 shows the efficiency and power loss of the DC3113A with a 3.3V input in both operation modes.

The DC3113A is optimized for a 4A to 12A, 8A/μs load step transient. A fast load step transient circuit is placed on the back of the demo board to measure the load step response of the converter.

The DC3113A 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 LTC3311-1 data sheet gives a complete description of the part and its application information. The data sheet must be read in conjunction with this demo manual. The LTC3311-1 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.

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