Datasheet

LTC3861-1
1
38611fa
For more information www.linear.com/LTC3861-1
Typical applicaTion
DescripTion
Dual, Multiphase Step-Down
Voltage Mode DC/DC Controller
with Accurate Current Sharing
The LTC
®
3861-1 is a dual PolyPhase
®
synchronous step-
down switching regulator controller for high current
distributed power systems, digital signal processors, and
other telecom and industrial DC/DC power supplies. It uses
a constant-frequency voltage mode architecture combined
with very low offset, high bandwidth error amplifiers and
a remote output sense differential amplifier for excellent
transient response and output regulation.
The controller incorporates lossless inductor DCR current
sensing to maintain current balance between phases and to
provide overcurrent protection. The chip operates from a
V
CC
supply between 3V and 5.5V and is designed for step-
down conversion from V
IN
between 3V and 24V to output
voltages between 0.6V and V
CC
– 0.5V.
Inductor current reversal is disabled during soft-start to
safely power prebiased loads. The constant operating
frequency can be synchronized to an external clock or
linearly programmed from 250kHz to 2.25MHz. Up to six
LTC3861-1 controllers can operate in parallel for 1-, 2-, 3-,
4-, 6- or 12-phase operation.
The LTC3861-1 is pin-to-pin compatible with the LTC3860.
It is available in a 32-pin 5mm × 5mm QFN package. The
LTC3861is a
36-pin QFN version of the LTC3861-1, which
has dual differential output voltage sense amplifiers.
FeaTures
applicaTions
n
Operates with Power Blocks, DrMOS or External
Gate Drivers and MOSFETs
n
Constant-Frequency Voltage Mode Control with
Accurate Current Sharing
n
±0.75% 0.6V Voltage Reference
n
Differential Remote Output Voltage Sense Amplifier
n
Multiphase Capability—Up to 12-Phase Operation
n
Programmable Current Limit
n
Safely Powers a Prebiased Load
n
Programmable or PLL-Synchronizable Switching
Frequency Up to 2.25MHz
n
Lossless Current Sensing Using Inductor DCR or
Precision Current Sensing with Sense Resistor
n
V
CC
Range: 3V to 5.5V
n
V
IN
Range: 3V to 24V
n
Power Good Output Voltage Monitor
n
Output Voltage Tracking Capability
n
Programmable Soft-Start
n
Available in a 32-Pin 5mm × 5mm QFN Package
n
High Current Distributed Power Systems
n
DSP, FPGA and ASIC Supplies
n
Datacom and Telecom Systems
n
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
VSNSOUT
VSNSP
VSNSN
CONFIG
V
CC
FREQ
FB2
I
LIM2
FB1
COMP1,2
SS1,2
VINSNS
IN
V
LOGIC
V
CC
BOOST
GND
TG
TS
BG
RUN1,2
I
LIM1
ISNS1P
ISNS1N
ISNS2N
ISNS2P
LTC3861-1
PWM1
LTC4449
V
IN
, 7V TO 14V
V
IN
0.47µH
SGND CLKIN
PWM2
180µF
1µF
0.22µF
0.22µF
V
CC
V
CC
0.22µF
100pF
1nF
0.1µF
1nF
13k
221Ω
59k
2.87k
2.87k
20k
220pF
V
OUT
V
IN
, 7V TO 14V
V
CC
IN
V
LOGIC
V
CC
BOOST
GND
TG
TS
BG
LTC4449
0.47µH
0.22µF
38611 TA01
330µF
× 6
100µF
× 4
V
OUT
1.2V
60A
I
AVG
20k
28.7k

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