Corp.'s LTC3852 is a low/wide
input voltage (2.7 to 5.5V or 4-38V) synchronous step-down dc/dc controller.
The device's onboard charge pump provides 5V bias to drive low RDS(ON) and standard logic-level power MOSFETs
from a 3.3V nominal supply. Since the LTC3852's internal charge pump and dc/dc controller are independent, the charge
pump output can provide 5V to power the internal gate drivers, and the dc/dc
converter power stage can draw power from another source, up to 38V maximum.
Output currents up to 25A can be supplied over an output voltage range from
0.8V to 99 percent of VIN (2.7V-5.5V),
making the LTC3852 useful for 3.3V-powered point-of-load applications.
A constant-frequency current-mode architecture allows a selectable fixed or
phase-lockable (PLL) frequency from 250kHz to 750kHz . Selectable Burst Mode
operation, pulse skip or forced continuous mode is user controlled to optimize
light load efficiency. OPTI-LOOP compensation allows the transient response to
be optimized over a wide range of output capacitance and ESR values, including
all ceramic input and output capacitors. Output current sensing is accomplished
by measuring the voltage drop across the output inductor (DCR) for highest
efficiency, or by using an optional sense resistor in series with the inductor
for highest accuracy. Current foldback limits MOSFET heat dissipation during
short-circuit and overload conditions.
The LTC3852 has adjustable soft-start or tracking to control the turn-on
characteristics of the supply, and features a precision 0.8V reference with an
accuracy of Â±1.25 percent over a -40 to 125C operating temperature range. With
a maximum duty cycle of 99 percent, the LTC3852 has a very low dropout voltage,
a useful feature for extending run times in battery-powered applications.
The LTC3852 is available in a thermally enhanced 3 x 5mm QFN-24 package.
Two different shape-shifting polymers have been announced from two different universities: Wyss Institute at Harvard University and Zhejiang University in eastern China. Both of them change their shapes when immersed in water, and the one from Wyss Institute was made with 3D-printing techniques.
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