DESCRIPTION
Demonstration circuit 2719A is a high performance bidirectional
buck-boost converter featuring the LT®8708/
LT8708-1 that can operate from input voltages above,
below or equal to the output voltage. The demo board
input range is 10.5V to 14.5V (25VMAX). The output voltage
is set at 14.5V and the output current limit at 40A.
The board can operate in both forward and reverse mode.
The controller has integrated input voltage and output
voltage regulators and two sets of input and output current
regulators that control current flow in forward or
reverse direction. Features are included that simplify bidirectional
power conversion in battery/capacitor backup
systems and other applications that may need regulation
of VIN, VOUT, IIN and/or IOUT.
While the current mode control limits the inductor current
both in normal and in reverse direction these current limits
have some variation as input/output voltage changes.
The forward and reverse input and output current regulators
offer four accurate current limits that can be set
individually.
The input voltage regulator is often used in applications
with high impedance power sources and will reduce the
forward current if the input voltage drops below the set
point. When operating with reverse current flow, the input
voltage regulator regulates the voltage at the input side.
The operating mode of the controller is determined
through the MODE pin (jumper JP9 Pins 5 to 12) and
can be set to discontinuous mode, hybrid discontinuous
mode, forced continuous mode and Burst Mode®
operation.
The LT8708 is capable of bidirectional operation when
operating in the continuous conduction mode (CCM).
DCM, HCM and Burst Mode operation only allow power to
flow in one direction. Additional circuitry may be needed
depending on the application.