LT8705A - 80V VIN and VOUT Synchronous 4-Switch Buck- Boost DC/DC Controller


  • Single Inductor Allows VIN Above, Below, or Equal to Regulated VOUT
  • VIN Range 2.8V (Need EXTVCC > 6.4V) to 80V
  • VOUT Range: 1.3V to 80V
  • Quad N-Channel MOSFET Gate Drivers
  • Synchronous Rectification: Up to 98% Efficiency
  • Input and Output Current Monitor Pins
  • Synchronizable Fixed Frequency: 100kHz to 400kHz
  • Integrated Input Current, Input Voltage, Output Current and Output Voltage Feedback Loops
  • Improved Light Load Transition from DCM to FCM
  • Improved IMON_OUT, IMON_IN Offset When Cold
  • Clock Output Usable To Monitor Die Temperature

Typical Application

LT8705A Typical Application
LT8705A Typical Application


The LT®8705A is a high performance buck-boost switching regulator controller that operates from input voltages above, below or equal to the output voltage. The part has integrated input current, input voltage, output current and output voltage feedback loops. With a wide 2.8V to 80V input and 1.3V to 80V output range, the LT8705A is compatible with most solar, automotive, telecom and battery-powered systems. The LT8705A is an improved pin compatible version of the LT8705 and is recommended for new designs. See LT8705A vs LT8705 in the Applications Information section for more information.

The LT8705A includes a MODE pin to select among Burst Mode® operation, discontinuous or continuous conduction mode at light loads. Additional features include a 3.3V/12mA LDO, a synchronizable fixed operating frequency, and onboard gate drivers.

LT8705A Improved, pin-to-pin compatible version of LT8705.  Recommended for all new designs


CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.

For complete and up to date package information and drawings, please refer to our packaging page

Part Number Package Code Temp Package
LT8705AEFE#PBF TSSOP-38 FE E 05-08-1865 Yes
LT8705AEFE#TRPBF TSSOP-38 FE E 05-08-1865 Yes
LT8705AEUHF#PBF 5x7 QFN-38 UHF E 05-08-1701 Yes
LT8705AEUHF#TRPBF 5x7 QFN-38 UHF E 05-08-1701 Yes
LT8705AHFE#PBF TSSOP-38 FE H 05-08-1865 Yes
LT8705AHFE#TRPBF TSSOP-38 FE H 05-08-1865 Yes
LT8705AIFE#PBF TSSOP-38 FE I 05-08-1865 Yes
LT8705AIFE#TRPBF TSSOP-38 FE I 05-08-1865 Yes
LT8705AIUHF#PBF 5x7 QFN-38 UHF I 05-08-1701 Yes
LT8705AIUHF#TRPBF 5x7 QFN-38 UHF I 05-08-1701 Yes
LT8705AMPFE#PBF TSSOP-38 FE MP 05-08-1865 Yes
LT8705AMPFE#TRPBF TSSOP-38 FE MP 05-08-1865 Yes

LT8705A Package Drawing
LT8705A Package Drawing

Order Info

  • Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
  • Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
  • Please refer to our general ordering information or the product datasheet for more details

Package Variations and Pricing

Part Number Package Temp Price
LT8705AEFE#PBF TSSOP-38 E $8.50 $5.95 Yes
LT8705AEFE#TRPBF TSSOP-38 E $8.56 $6.01 Yes
LT8705AEUHF#PBF 5x7 QFN-38 E $8.50 $5.95 Yes
LT8705AEUHF#TRPBF 5x7 QFN-38 E $8.56 $6.01 Yes
LT8705AHFE#PBF TSSOP-38 H $9.76 $6.83 Yes
LT8705AHFE#TRPBF TSSOP-38 H $9.82 $6.89 Yes
LT8705AIFE#PBF TSSOP-38 I $9.40 $6.58 Yes
LT8705AIFE#TRPBF TSSOP-38 I $9.46 $6.64 Yes
LT8705AIUHF#PBF 5x7 QFN-38 I $9.40 $6.58 Yes
LT8705AIUHF#TRPBF 5x7 QFN-38 I $9.46 $6.64 Yes
LT8705AMPFE#PBF TSSOP-38 MP $25.37 $17.76 Yes
LT8705AMPFE#TRPBF TSSOP-38 MP $25.43 $17.82 Yes
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* The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Linear Technology sales office or authorized distributor.

Demo Boards

Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Part Number Description Price Documentation
DC2285A LT8705AEUHF Demo Board | VIN = 36V to 75V, VOUT = 48V @18A $349.00
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Click here to view our complete list of demo boards


  • High Voltage Buck-Boost Converters
  • Input or Output Current Limited Converters

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Design Tools


LTspice® software is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. Click here to download LTspice

To launch a ready to run LTspice demonstration circuit for this part:

To explore other ready to run LTspice demonstration circuits, please visit our Demo Circuits Collection.

Models for the following parts are available in LTspice:


The LTpowerCAD design tool is a complete power supply design tool program that can significantly ease the tasks of power supply design. It guides users to a solution, selects power stage components, provides detailed power efficiency, shows quick loop bode plot stability and load transient analysis, and can export a final design to LTspice for simulation. Click here to download LTpowerCAD

Design tools for the following parts are available in LTpowerCAD:

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