Features and Benefits
- Slave Chip of LT8708 to Deliver Additional Power
- Good Current Matching to the Average Output Current of LT8708 Through Current Regulation
- Easily Paralleled with LT8708 Through Four Pins
- Synchronized Start-Up with LT8708
- Same Conduction Modes as LT8708
- Synchronous Rectification: Up to 98% Efficiency
- Frequency Range: 100kHz to 400kHz
- Available in 40-Lead (5mm × 8mm) QFN with High Voltage Pin Spacing and 64-Lead (10mm × 10mm) eLQFP
- AEC-Q100 in Progress
The LT8708-1 is a high performance buck-boost switching regulator controller that is paralleled with the LT8708 to add power and phases to an LT8708 system. The LT8708-1 always operates as a slave to the master LT8708 and has the capability of delivering as much current or power as the master. One or more slaves can be connected to a single master, proportionally increasing power and current capability of the system.
The LT8708-1 has the same conduction modes as LT8708, allowing the LT8708-1 to conduct current and power in the same direction(s) as the master. The master controls the overall current and voltage limits for an LT8708 multiphase system, and the slaves comply with these limits.
LT8708-1s can be easily paralleled with the LT8708 by connecting four signals together. Two additional current limits (forward VIN current and reverse VIN current) are available on each slave that can be set independently.
- High Voltage Buck-Boost Converters
- Bidirectional Charging Systems
- Automotive 48V Systems
Product Lifecycle Recommended for New Designs
This product has been released to the market. The data sheet contains all final specifications and operating conditions. For new designs, ADI recommends utilization of these products.
Evaluation Kits (1)
Demonstration circuit 2719A is a high performance bidirectional buck-boost converter featuring the LT8708/ 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.
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
Models for the following parts are available in LTspice:
LTpowerCAD® is a power supply design program which selects power stage components, provides detailed power efficiency, shows quick loop Bode plot stability and load transient analysis, and can export to LTspice for simulation.
Design tools for the following parts are available in LTpowerCAD:
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