LTC3861-1
Dual, Multiphase Step-Down
Voltage Mode DC/DC Controller
with Accurate Current Sharing
Fea T Descrip T
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Operates with Power Blocks, DrMOS or External
The LTC 3861-1 is a dual PolyPhase synchronous step-
Gate Drivers and MOSFETs
down switching regulator controller for high current
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Constant-Frequency Voltage Mode Control with distributed power systems, digital signal processors, and
Accurate Current Sharing other telecom and industrial DC/DC power supplies. It uses
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0.75% 0.6V Voltage Reference a constant-frequency voltage mode architecture combined
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with very low offset, high bandwidth error amplifiers and
Differential Remote Output Voltage Sense Amplifier
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a remote output sense differential amplifier for excellent
Multiphase CapabilityUp to 12-Phase Operation
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transient response and output regulation.
Programmable Current Limit
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Safely Powers a Prebiased Load
The controller incorporates lossless inductor DCR current
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Programmable or PLL-Synchronizable Switching
sensing to maintain current balance between phases and to
Frequency Up to 2.25MHz
provide overcurrent protection. The chip operates from a
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Lossless Current Sensing Using Inductor DCR or
V supply between 3V and 5.5V and is designed for step-
CC
Precision Current Sensing with Sense Resistor
down conversion from V between 3V and 24V to output
IN
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V Range: 3V to 5.5V
CC
voltages between 0.6V and V 0.5V.
CC
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V Range: 3V to 24V
IN
Inductor current reversal is disabled during soft-start to
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Power Good Output Voltage Monitor
safely power prebiased loads. The constant operating
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Output Voltage Tracking Capability
frequency can be synchronized to an external clock or
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Programmable Soft-Start
linearly programmed from 250kHz to 2.25MHz. Up to six
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Available in a 32-Pin 5mm 5mm QFN Package
LTC3861-1 controllers can operate in parallel for 1-, 2-, 3-,
4-, 6- or 12-phase operation.
a T
The LTC3861-1 is pin-to-pin compatible with the LTC3860.
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High Current Distributed Power Systems
It is available in a 32-pin 5mm 5mm QFN package. The
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DSP, FPGA and ASIC Supplies
LTC3861is a 36-pin QFN version of the LTC3861-1, which
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Datacom and Telecom Systems
has dual differential output voltage sense amplifiers.
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Industrial Power Supplies
L, LT, LTC, LTM, PolyPhase, Linear Technology and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners. Protected by U.S. Patents, including 6144194, 5055767
Typical a T
V , 7V TO 14V
IN
LTC4449
180F
IN
GND
V , 7V TO 14V
IN
V TG
V
CC LOGIC
V TS
CC
V
CC V VINSNS PWM1
CC
0.47H
BOOST BG
FREQ
1F
FB2
28.7k
LTC3861-1
59k 0.22F
RUN1,2
I
LIM2 2.87k
I
LIM1
VSNSOUT
ISNS1P V
0.22F OUT
V VSNSP
OUT ISNS1N 1.2V
VSNSN 330F 100F
ISNS2N 60A
CONFIG 0.22F 6 4
ISNS2P
V
IN
1nF 2.87k
LTC4449
PWM2 IN GND
20k 221
0.47H
V
FB1 V TG
CC LOGIC
I
AVG
38611 TA01
V TS
CC
COMP1,2 SS1,2 SGND CLKIN
BOOST BG
1nF
20k 13k
220pF 0.1F 100pF
0.22F
38611fb
1
For more information www.linear.com/LTC3861-1
ion pplica
ions pplica
ion uresLTC3861-1
a Te m aximum r a T p in c F T
(Note 1)
V Voltage .................................................. 0.3V to 6V
CC
TOP VIEW
VINSNS Voltage ......................................... 0.3V to 30V
RUN1, RUN2 Voltage ........................0.3V to V + 0.3V
CC
ISNS1P, ISNS1N,
32 31 30 29 28 27 26 25
V 1 24 RUN1
ISNS2P, ISNS2N ........................... 0.3V to (V + 0.1V) CC
CC
FB1 2 23 I
LIM1
All Other Pins ................................0.3V to (V + 0.3V)
CC
COMP1 ISNS1P
3 22
Operating Junction Temperature Range
VSNSOUT 4 21 ISNS1N
33
(Notes 2, 3) ............................................ 40C to 125C
SGND
VSNSN 5 20 ISNS2N
Storage Temperature Range .................. 65C to 150C
VSNSP 6 19 ISNS2P
COMP2 7 18 I
LIM2
FB2 8 17 RUN2
9 10 11 12 13 14 15 16
UH PACKAGE
32-LEAD (5mm 5mm) PLASTIC QFN
T = 125C, = 34C/W
JMAX JA
EXPOSED PAD (PIN 33) IS SGND, MUST BE SOLDERED TO PCB
o r Der i n F T
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3861EUH-1#PBF LTC3861EUH-1#TRPBF 38611 32-Lead (5mm 5mm) Plastic QFN 40C to 125C
LTC3861IUH-1#PBF LTC3861IUH-1#TRPBF 38611 32-Lead (5mm 5mm) Plastic QFN 40C to 125C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: