LTC3731 - 3-Phase, 600kHz, Synchronous Buck Switching Regulator Controller


  • 3-Phase Current Mode Controller with Onboard MOSFET Drivers
  • ±5% Output Current Matching Optimizes Thermal Performance and Size of Inductors and MOSFETs
  • Differential Amplifier Accurately Senses VOUT
  • ±1% VREF Accuracy Over Temperature
  • VOUT Range: 0.6V to 5.5V without Diffamp
  • VOUT Range: 0.6V to (VCC – 1.2V) with Diffamp
  • 250kHz to 600kHz Per Phase, PLL, Fixed Frequency
  • PWM, Stage Shedding™ or Burst Mode® Operation
  • OPTI-LOOP® Compensation Minimizes COUT
  • Adjustable Soft-Start Current Ramping
  • Short-Circuit Shutdown Timer with Defeat Option
  • Overvoltage Soft Latch
  • Adjustable Undervoltage Lockout Threshold
  • Selectable Phase Output for Up to 12-Phase Operation
  • Available in 5mm × 5mm QFN and 36-Pin Narrow (0.209") SSOP Packages

Typical Application

LTC3731 Typical Application


The LTC3731 is a PolyPhase synchronous step-down switching regulator controller that drives all N-channel external power MOSFET stages in a phase-lockable fixed frequency architecture. The 3-phase controller drives its output stages with 120° phase separation at frequencies of up to 600kHz per phase to minimize the RMS current losses in both the input and output filter capacitors. The 3-phase technique effectively triples the fundamental frequency, improving transient response while operating each controller at an optimal frequency for efficiency and ease of thermal design. Light load efficiency is optimized by using a choice of output Stage Shedding or Burst Mode operation.

A differential amplifier provides true remote sensing of both the high and low side of the output voltage at the point of load. The precision reference supports output voltages from 0.6V to 6V.

Soft-start and a defeatable, timed short-circuit shutdown protect the MOSFETs and the load. Current foldback provides protection for the external MOSFETs under short-circuit or overload conditions.


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
LTC3731CG#PBF SSOP-24 G C 05-08-1640 (G24) Yes
LTC3731CG#TRPBF SSOP-24 G C 05-08-1640 (G24) Yes
LTC3731CUH#PBF 5x5 QFN-32 UH C 05-08-1693 Yes
LTC3731CUH#TRPBF 5x5 QFN-32 UH C 05-08-1693 Yes
LTC3731IG#PBF SSOP-24 G I 05-08-1640 (G24) Yes
LTC3731IG#TRPBF SSOP-24 G I 05-08-1640 (G24) Yes
LTC3731IUH#PBF 5x5 QFN-32 UH I 05-08-1693 Yes
LTC3731IUH#TRPBF 5x5 QFN-32 UH I 05-08-1693 Yes

LTC3731 Package Drawing
LTC3731 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
LTC3731CG#PBF SSOP-24 C $6.16 $4.35 Yes
LTC3731CG#TRPBF SSOP-24 C $4.45 Yes
LTC3731CUH#PBF 5x5 QFN-32 C $6.52 $4.55 Yes
LTC3731CUH#TRPBF 5x5 QFN-32 C $4.65 Yes
LTC3731IG#PBF SSOP-24 I $6.88 $4.80 Yes
LTC3731IG#TRPBF SSOP-24 I $4.90 Yes
LTC3731IUH#PBF 5x5 QFN-32 I $5.89 $4.95 Yes
LTC3731IUH#TRPBF 5x5 QFN-32 I $5.05 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
DC438A LTC3731CG | 3-Phase, Vin = 9V to 14V, Vout = 2.5V/1.8V @ 60A $150.00
DC558A LTC3731CUH Demo Board | 3-Phase, Vin = 5V to 14V, Vout = 1.5V/60A Contact Factory
DC561A-A LTC3731CUH (x4) | 12-Phase, 10V - 14Vin, 1.5Vout @ 180A $175.00
DC561A-B LTC3731CUH (x2) | 6-Phase, 10V - 14Vin, 1.5Vout @ 90A Contact Factory
DC721A-A LTC3738CUHF/LTC3731CUH Demo Board | 6-Phase, 8V ≤ VIN ≤ 14V, Vout = VRM9.X / 10.X @ 120A Contact Factory
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Click here to view our complete list of demo boards


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Design Tools


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