LTC3649 - 60V, 4A Synchronous Step-Down Regulator with Rail-to-Rail Programmable Output


  • Wide VIN Range: 3.1V to 60V
  • Wide VOUT Range: 0V to (VIN – 0.5V)
  • Single Resistor VOUT Programming
  • Integrated 110mΩ Top N-Channel/50mΩ Bottom N-Channel MOSFETs
  • 95% Efficiency with 12VIN and 5VOUT
  • Regulated IQ: 440μA, Shutdown IQ: 18μA
  • Accurate Current Monitoring (±4%) without Sense Resistor
  • Accurate Resistor Programmable Frequency (300kHz to 3MHz) with ±50% Frequency Sync Range
  • Accurate Programmable Output Current
  • Input Voltage Regulation for MPPT Applications
  • ±0.8% Output Voltage Accuracy
  • Peak Current Mode Operation
  • Programmable Wire Drop Compensation
  • Burst Mode® Operation, Forced Continuous Mode
  • Internal Compensation and Programmable Soft-Start
  • Overtemperature Protection
  • Available in Thermally Enhanced 28-Lead (4mm × 5mm) QFN and TSSOP Packages

Typical Application

LTC3649 Typical Application
LTC3649 Typical Application


The LTC®3649 is a high efficiency 60V, 4A synchronous monolithic step-down regulator. The regulator features a single resistor programmable output voltage, internal compensation and high efficiencies over a wide VOUT range.

The step-down regulator operates from an input voltage range of 3.1V to 60V and provides an adjustable rail-to-rail output range from (VIN – 0.5V) to ground while delivering up to 4A of output current. The switching frequency is also adjusted with an external resistor. A user-selectable mode input is provided to allow the user to trade off ripple noise for efficiency at light loads; Burst Mode operation provides the highest efficiency at light loads, while forced continuous mode provides low output ripple. The MODE/ SYNC pin can also be used to allow the user to synchronize the switching frequency to an external clock.

The LTC3649 operates with a peak current mode architecture that allows for fast transient response with inherent cycle-to-cycle current limit protection. It also features programmable output current limit, current monitoring and input voltage regulation.


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
LTC3649EFE#PBF TSSOP-28 FE E 05-08-1663 (EB) Yes
LTC3649EFE#TRPBF TSSOP-28 FE E 05-08-1663 (EB) Yes
LTC3649EUFD#PBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3649EUFD#TRPBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3649IFE#PBF TSSOP-28 FE I 05-08-1663 (EB) Yes
LTC3649IFE#TRPBF TSSOP-28 FE I 05-08-1663 (EB) Yes
LTC3649IUFD#PBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LTC3649IUFD#TRPBF 4x5 QFN-28 UFD I 05-08-1712 Yes

LTC3649 Package Drawing
LTC3649 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
LTC3649EFE#PBF TSSOP-28 E $8.43 $5.90 Yes
LTC3649EFE#TRPBF TSSOP-28 E $5.96 Yes
LTC3649EUFD#PBF 4x5 QFN-28 E $8.07 $5.65 Yes
LTC3649EUFD#TRPBF 4x5 QFN-28 E $5.71 Yes
LTC3649IFE#PBF TSSOP-28 I $9.70 $6.79 Yes
LTC3649IFE#TRPBF TSSOP-28 I $6.85 Yes
LTC3649IUFD#PBF 4x5 QFN-28 I $9.29 $6.50 Yes
LTC3649IUFD#TRPBF 4x5 QFN-28 I $6.56 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
DC2112A LTC3649EUFD Demo Board | 4V ≤ VIN ≤ 60V; VOUT = 3.3V or 5V @ 4A Contact Factory
DC2113A LTC3649 Demo Board | Sync Buck, 3.1V ≤ VIN ≤ 60V, Vout = 3.3V/5V @ 4A $150.00
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Click here to view our complete list of demo boards


  • Industrial Applications
  • Automotive Applications

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