Arrow Plastic 3M Network Card - Manual (Page 23)

The LTC3853 is a highly efficient, synchronous step-down
switching regulator, DC/DC controller with three outputs
and numerous features that include output voltage tracking,
Burst Mode® operation and pulse skipping, which safely
powers pre-biased loads.
The latest device in Linear Technology’s next generation of step-
down controllers, the LTC3853, complements the LTC3850 dual
output and LTC3851 single output controllers. It has a 4.5V to
24V (28Vmax) input voltage range and can be powered from most
intermediate bus voltages and battery chemistries.
The illustration shows a simplified schematic and the package
of the LTC3853 step-down DC/DC converter. Strong onboard
gate drivers power all N-channel MOSFET stages. Each stage
can produce output currents up to 20A per channel with output
voltages ranging from 0.8V to 13.5V on one channel and from
0.8V to 5.5V on the other two channels, making it ideal for point
of load regulator requirements in medical, datacom, telecom,
industrial, automotive applications, displays and set top boxes.
Its constant frequency, current-mode architecture provides a
selectable fixed or synchronisable frequency from 250kHz to
750kHz using Phase Lock Loop (PLL). Operating the three channels
120º out of phase minimises power loss and supply noise. The
LTC3853 can also be configured with one output channel 180º
out of phase from channels two and three. True current-mode
control enables stable operation over a wide range of output
capacitance and ESR values, including all ceramic capacitors for the
smallest solution size. It has current foldback to limit MOSFET heat
dissipation during short circuit and overload conditions.
Additionally, the LTC3853 can be configured with DCR (inductor)
current sensing to maximise efficiency and has a minimum on time
of only 90ns for applications requiring high step-down ratios. An
onboard regulator develops its own internal IC bias voltage and
an adjustable soft-start controls the turn-on time. A precision 0.8V
reference has ±1% accuracy over a -40ºC to +125ºC operating
temperature range.
With up to 98% duty cycle, the LTC3853 has a very low dropout
voltage, a useful feature for extending run times in battery
powered applications.
The LTC3853 is offered in a thermally enhanced 6mm x 6mm
QFN-40 package.
Features
U
Onboard 5V linear bias voltage regulator
U Safely powers pre-biased loads
U Output voltage tracking
U Burst mode operation
U Pulse skipping
U Input voltage range: 4.5V to 24V, 28Vmax
U Output current: <20A per channel
U Powerful onboard MOSFET gate drivers
U Output voltage: 0.8V to 13.5V on one channel, 0.8V to 5.5V
on two channels
U <98% duty cycle
U Operating temperature range: -40ºC to +125ºC with ±1%
reference voltage accuracy
U Fixed or synchronisable operating frequency from 250kHz to
750kHz using PLL
U QFN-40, 6mm x 6mm package
Applications
U
Point of load regulators
U Medical
U Data and telecom
U Industrial
U Automotive
U Displays
U Set top boxes
For further information, including the LTC3853 Datasheet, please complete the
reply slip or visit
http://www.arrowne.com/innov/in218/f_1455.shtml
Triple Output, Multiphase, Synchronous Step-Down
Controller
23
POWER AND LINEAR IC
SOLUTIONS
Highly efficient, switching step-down DC/DC controller has numerous features
ENQUIRY 1455
Linear
Technology
LTC3853
Datasheet
available!
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