LTC3811
High Speed Dual,
Multiphase Step-Down DC/DC
Controller
FEATURES
DESCRIPTION
The LTC®3811 is a dual, PolyPhase® synchronous step-
down switching regulator controller optimized for output
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Fixed Frequency, Peak Current Mode Control
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±±0.5 Output ꢀccuracy Oꢁer Temperature
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Optimized for Low V
ꢀpplications (Up to 303V)
voltages up to 3.3V. The LTC3811 includes high bandwidth
error amplifiers as well as a high speed differential remote
sense amplifier. The sense voltage range is programmable
from24mVto85mV,allowingtheuseofeithertheinductor
DCR or a discrete sense resistor. Multiphase operation is
made possible using the MODE/SYNC input, the CLKOUT
output and the PHASEMODE control pin, allowing 1-, 2-,
3-, 4-, 6- or 12-phase operation.
OUT
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Dual or Single Output, Multiphase Operation
Wide V Range: 40.V to 3±V Operation
IN
High Speed Differential Remote Sense ꢀmplifier
Inductor DCR or Sense Resistor Capable
ꢀdjustable Peak Current Sense Voltage:
24mV to 8.mV
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Very Low Duty Cycle Operation: t
Powerful Internal Gate Drivers
Output Voltage Soft-Start, Tracking and Sequencing
Programmable Load Line for Reduced C
= 6.ns (Typ)
ON(MIN)
Large internal gate drivers minimize switching losses and
allow the use of multiple power MOSFETs connected in
parallel for high current applications.
OUT
Clock Input and Output for Up to 12-Phase Operation
Fixed Frequency Operation from 250kHz to 750kHz
PLL Synchronization from 150kHz Up to 900kHz
Selectable CCM or DCM Operation
TheoperatingfrequencyoftheLTC3811canbeprogrammed
from 250kHz to 750kHz and can also be synchronized to
an external clock using the internal PLL.
Available in 5mm × 7mm QFN and G36 Packages
Tracking and sequencing are possible with the LTC3811,
and soft-start is programmed with an external capacitor.
Shutdown reduces supply current to 20μA.
, LT, LTC, LTM and PolyPhase are registered trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 5481178, 6304066, 5929620, 6177787, 6144194,
6580258, 5705919.
APPLICATIONS
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Network Servers
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High Current ASIC Supplies
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Low Voltage Power Distribution
TYPICAL APPLICATION
Dual Output, 2-Phase Tracking Core and I/O Supply
V
IN
Load Step
4.5V TO 14V
V
INTV
DRV
IN
CC
CC
TG2
TG1
V
OUT
100mV/DIV
BOOST1
SW1
BOOST2
SW2
BG1
BG2
RUN1
RUN2
PGND
LTC3811
+
+
SENSE1
SENSE2
I
L
–
–
5A/DIV
SENSE1
RNG1
SENSE2
+
DIFF/IN
–
DIFF/IN
RNG2
FB1
DIFF/OUT
FB2
V
OUT1
2V
15A
3811 TA01b
V
1.5V
15A
OUT2
V
V
= 12V
20μs/DIV
IN
COMP1
COMP2
= 2V
OUT
OUT
SS/TRACK1 SGND SS/TRACK2
I
= 0A to 12.5A
3811 TA01a
3811f
1