LT8705 - 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 and Output Voltage Feedback Loops
  • Clock Output Usable To Monitor Die Temperature
  • Available in 38-Lead (5mm × 7mm) QFN and TSSOP Packages with the TSSOP Modified for Improve Voltage Operation

Typical Application

LT8705 Typical Application
LT8705 Typical Application


The LT®8705 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 LT8705 is compatible with most solar, automotive, telecom and battery-powered systems.

The LT8705 includes servo pins to indicate which feedback loops are active. The MODE pin selects 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, onboard gate drivers, adjustable UVLO, along with input and output current monitoring with programmable maximum levels.


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

Part Number Package Code Temp Package
LT8705EFE#PBF TSSOP-38 FE E 05-08-1865 RoHS
LT8705EFE#TRPBF TSSOP-38 FE E 05-08-1865 RoHS
LT8705EUHF#PBF 5x7 QFN-38 UHF E 05-08-1701 RoHS
LT8705EUHF#TRPBF 5x7 QFN-38 UHF E 05-08-1701 RoHS
LT8705HFE#PBF TSSOP-38 FE H 05-08-1865 RoHS
LT8705HFE#TRPBF TSSOP-38 FE H 05-08-1865 RoHS
LT8705IFE#PBF TSSOP-38 FE I 05-08-1865 RoHS
LT8705IFE#TRPBF TSSOP-38 FE I 05-08-1865 RoHS
LT8705IUHF#PBF 5x7 QFN-38 UHF I 05-08-1701 RoHS
LT8705IUHF#TRPBF 5x7 QFN-38 UHF I 05-08-1701 RoHS
LT8705MPFE#PBF TSSOP-38 FE MP 05-08-1865 RoHS
LT8705MPFE#TRPBF TSSOP-38 FE MP 05-08-1865 RoHS

LT8705 Package Drawing
LT8705 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
LT8705EFE#PBF TSSOP-38 E $8.50 $5.95 Yes
LT8705EFE#TRPBF TSSOP-38 E $6.01 Yes
LT8705EUHF#PBF 5x7 QFN-38 E $8.50 $5.95 Yes
LT8705EUHF#TRPBF 5x7 QFN-38 E $6.01 Yes
LT8705HFE#PBF TSSOP-38 H $9.76 $6.83 Yes
LT8705HFE#TRPBF TSSOP-38 H $6.89 Yes
LT8705IFE#PBF TSSOP-38 I $9.40 $6.58 Yes
LT8705IFE#TRPBF TSSOP-38 I $6.64 Yes
LT8705IUHF#PBF 5x7 QFN-38 I $9.40 $6.58 Yes
LT8705IUHF#TRPBF 5x7 QFN-38 I $6.64 Yes
LT8705MPFE#PBF TSSOP-38 MP $25.37 $17.76 Yes
LT8705MPFE#TRPBF TSSOP-38 MP $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
DC1924A LT8705EUHF Demo Board | 36V ≤ VIN ≤ 80V; Vout = 48V @ 5A $250.00
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  • High Voltage Buck-Boost Converters
  • Input or Output Current Limited Converters

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Design Tools


The LTpowerCAD II 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:


LTspice® IV 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 IV

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Models for the following parts are available in LTspice IV:

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