LTC3871
®
Bidirectional PolyPhase
Synchronous Buck or Boost Controller
FEATURES
DESCRIPTION
The LTC®3871 is a high performance bidirectional buck or
boost switching regulator controller that operates in either
buck or boost mode on demand. It regulates in buck mode
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Unique Architecture Allows Dynamic Regulation of
Input Voltage, Output Voltage or Current
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V
V
Voltages Up to 100V
Voltages Up to 30V
HIGH
LOW
from V
-to-V
and boost mode from V
-to-V
HIGH
LOW
LOW HIGH
Synchronous Rectification: Up to 97% Efficiency
LTC-Proprietary Advanced Current Mode Control
1% Voltage Regulation Accuracy Over Temperature
Accurate, Programmable Output Current Monitoring
and Regulation for Both Buck and Boost Operation
Selectable Buck and Boost Current Sense Limits
depending on a control signal, making it ideal for 48V/12V
automotive dual battery systems. An accurate current
programming loop regulates the maximum current that
can be delivered in either direction. The LTC3871 allows
both batteries to supply energy to the load simultaneously
by converting energy from one battery to the other.
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Programmable DRV /EXTV Optimizes Efficiency
CC
CC
Its proprietary constant-frequency current mode
architecture enhances the signal-to-noise ratio enabling
low noise operation and provides excellent current
matching between phases. Additional features include
discontinuous or continuous mode of operation, OV/UV
monitors, independent loop compensation for buck and
boost operation, accurate output current monitoring and
overcurrent protection.
Programmable V
Programmable V
UV and OV Thresholds
OV Threshold
HIGH
LOW
Phase-Lockable Frequency: 60kHz to 460kHz
Multiphase/Multi-ICs Operation Up to 12 Phases
Selectable CCM/DCM Modes
Thermally Enhanced 48-Lead LQFP Package
APPLICATIONS
L, LT, LTC, LTM, Linear Technology, the Linear logo, μModule, PolyPhase and OPTI-LOOP are
registered trademarks of Linear Technology Corporation. All other trademarks are the property
of their respective owners. Protected by U.S. Patents, including 5481178, 5705919, 5929620,
6177787, 6580258, 6100678, 6144154, 6304066.
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Automotive 48V/12V Dual Battery Systems
Backup Power Systems
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TYPICAL APPLICATION
High Efficiency Bidirectional Charger/Power Supply
V
HIGH
26V TO 58V
Buck-to-Boost Transition
OV
HIGH
EXTV
CC
UV
HIGH
VFB
LOW
BUCK
BOOST
BUCK
–
SNS1
ITH
HIGH
+
V
SNSD1
LOW
+
5V/DIV
SNSA1
DRV
BST1
I
CC
ITH
L
LOW
5A/DIV
TG1
SW1
BG1
SS
V
HIGH
V
12V
BATTERY
LOW
LTC3871
10V/DIV
BUCK BOOST
BUCK
SW
50V/DIV
VFB
HIGH
IMON
–
SNS2
3871 TA01b
FREQ
+
50μ/DIV
SNSD2
SNSA2
V
LOW
+
DRV
BST2
CC
OV
LOW
TG2
DRV
CC
SW2
V5
BG2
3871 TA01a
PINS NOT SHOWN IN THIS CIRCUIT:
CLKOUT, DRVSET, FAULT, ILIM, MODE,
PHSMD, RUN, SETCUR AND SYNC.
3871f
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For more information www.linear.com/LTC3871