DESCRIPTION
Demonstration circuit 3021A shows the LTC®3310S-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.
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
this 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.