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Analog Devices LT8708 | Demoboard DC2719A

LT8708/LT8708-1 80V VIN and VOUT Synchronous 4-Switch Buck-Boost DC/DC Controller with Flexible Bidirectional Capability

Overview

TopologyBuck-Boost Converter
Input voltage10.5-25 V
Switching frequency100-400 kHz
Output 114.5 V / 40 A

Description

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.

Features

  • Single Inductor Allows VIN Above, Below, or Equal to VOUT
  • Six Independent Forms of Regulation
  • VIN Current (Forward and Reverse)
  • VOUT Current (Forward and Reverse)
  • VIN and VOUT Voltage
  • Forward and Reverse Discontinuous Conduction Mode Supported
  • Supports MODE and DIR Pin Changes While Switching
  • VINCHIP Range 2.8V (Need EXTVCC > 6.4V) to 80V
  • VOUT Range: 1.3V to 80V
  • Synchronous Rectification: Up to 99% Efficiency
  • Available in 40-Lead (5mm × 8mm) QFN with High Voltage Pin Spacing

Typical applications

  • High Voltage Buck-Boost Converters / Bidirectional Charging System
  • Automotive 48V Systems

More information

Products

Order Code
Data­sheet
Simu­lation
Downloads
Status
Product series
L(mm)
f(mm)
C
Tol. C
VR(V (DC))
Size
Operating Temperature
Q(%)
RISO
Ceramic Type
W(mm)
H(mm)
Fl(mm)
Packaging
Pins
Type
Mount
IR(A)
Working Voltage(V (AC))
Color
Gender
Samples
WCAP-CSGP MLCCs 25 V(DC), 1.6 mm, –
Simu­lation
Status Activei| Production is active. Expected lifetime: >10 years.
Length1.6 mm
Capacitance100 pF
Capacitance±5% 
Rated Voltage25 V (DC)
Size0603 
Operating Temperature -55 °C up to +125 °C
Q-Factor1000 %
Insulation Resistance10 GΩ
Ceramic TypeNP0 Class I 
Width0.8 mm
Height0.8 mm
Pad Dimension0.4 mm
Packaging7" Tape & Reel 
WCAP-CSGP MLCCs 25 V(DC), 1.6 mm, –
Simu­lation
Status Activei| Production is active. Expected lifetime: >10 years.
Length1.6 mm
Capacitance470 pF
Capacitance±5% 
Rated Voltage25 V (DC)
Size0603 
Operating Temperature -55 °C up to +125 °C
Q-Factor1000 %
Insulation Resistance10 GΩ
Ceramic TypeNP0 Class I 
Width0.8 mm
Height0.8 mm
Pad Dimension0.4 mm
Packaging7" Tape & Reel 
WR-PHD Jumper, 2.44 mm, –
Simu­lation
Status Activei| Production is active. Expected lifetime: >10 years.
Product seriesWR-PHD Jumper
Length2.44 mm
Operating Temperature -40 °C up to +125 °C
Insulation Resistance1000 MΩ
PackagingBag 
Pins
Rated Current3 A
Working Voltage250 V (AC)
ColorBlack 
GenderJumper 
WA-SNSR Self-Retaining Spacer, 9.5 mm, 4.8 mm
Simu­lation
Status Activei| Production is active. Expected lifetime: >10 years.
Length9.5 mm
Drilling in Panel4.8 mm
Operating Temperature -30 °C up to +85 °C
ColorNatural 
WR-PHD Pin Header - Dual, 10.16 mm, –
Simu­lation
Status Activei| Production is active. Expected lifetime: >10 years.
Length10.16 mm
Operating Temperature -40 °C up to +105 °C
Insulation Resistance1000 MΩ
PackagingBag 
Pins
TypeStraight 
MountTHT 
Rated Current3 A
Working Voltage250 V (AC)
GenderPin Header 
WR-PHD Pin Header - Dual, 20.32 mm, –
Simu­lation
Status Activei| Production is active. Expected lifetime: >10 years.
Length20.32 mm
Operating Temperature -40 °C up to +105 °C
Insulation Resistance1000 MΩ
PackagingBag 
Pins16 
TypeStraight 
MountTHT 
Rated Current3 A
Working Voltage250 V (AC)
GenderPin Header 
WR-PHD Pin Header - Dual, 33.02 mm, –
Simu­lation
Status Activei| Production is active. Expected lifetime: >10 years.
Length33.02 mm
Operating Temperature -40 °C up to +105 °C
Insulation Resistance1000 MΩ
PackagingBag 
Pins26 
TypeStraight 
MountTHT 
Rated Current3 A
Working Voltage250 V (AC)
GenderPin Header