80V Synchronous 4-Switch Buck-Boost DC/DC
Controller with Flexible Bidirectional Capability
nn Single Inductor Allows VIN Above, Below, or
Equal to VOUT
nn Six Independent Forms of Regulation
nn VIN Current (Forward and Reverse)
nn VOUT Current (Forward and Reverse)
nn VIN and VOUT Voltage
nn Forward and Reverse Discontinuous Conduction
nn Supports MODE and DIR Pin Changes While Switching
nn VINCHIP Range 2.8V (Need EXTVCC > 6.4V) to 80V
nn VOUT Range: 1.3V to 80V
nn Synchronous Rectification: Up to 99% Efficiency
nn Available in 40-Lead (5mm × 8mm) QFN with High
Voltage Pin Spacing
nn High Voltage Buck-Boost Converters
nn Bidirectional Charging System
nn Automotive 48V Systems
The LT®8708 is a high performance buck-boost switching
regulator controller that operates from an input voltage
that can be above, below or equal to the output voltage.
Features are included to simplify bidirectional power
conversion in battery/capacitor backup systems and other
applications that may need regulation of VOUT, VIN, IOUT,
and/or IIN. Forward and reverse current can be monitored
and limited for the input and output sides of the converter.
All four current limits (forward input, reverse input, forward
output and reverse output) can be set independently using
four resistors on the PCB.
The MODE pin can select between discontinuous conduc-
tion mode (DCM), continuous conduction mode (CCM),
hybrid conduction mode (HCM) and Burst Mode® operation.
In combination with the DIR (direction) pin, the chip can be
configured to process power only from VIN to VOUT or only
from VOUT to VIN. With a wide 2.8V to 80V input and 1.3V
to 80V output range, the LT8708 is compatible with most
solar, automotive, telecom and battery-powered systems.
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RVS (0V) FWD (3V)
12V Bidirectional Dual Battery System with FHCM and RHCM
TG1 BOOST1 SW1 BG1 CSP CSN
GND BG2 SW2 BOOST2 TG2
SS SYNC CLKOUT
VBAT2 = 13.5V
IOUT = 15A
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