LT3641 - Dual Monolithic Buck Regulator with Power-On Reset and Watchdog Timer


  • High Voltage Buck Regulator:
    4V to 42V Operating Range
    1.3A Output Current
  • Input Transient Protection to 55V
  • Low Voltage Synchronous Buck Regulator:
    2.5V to 5.5V Input Voltage Range
    1.1A Output Current
  • Synchronizable, Adjustable 350kHz to 2.5MHz Switching Frequency
  • Programmable Power-On Reset Timer
  • Programmable Window Mode Watchdog Timer
  • Typical Quiescent Current: 290μA
  • Short-Circuit Robust
  • Programmable Soft-Start
  • Low Shutdown Current: IQ < 1μA
  • Thermal Shutdown
  • Available in Thermally Enhanced 28-Lead (4mm × 5mm) QFN and 28-Lead TSSOP Packages

Typical Application

LT3641 Typical Application
LT3641 Typical Application
LT3641 Typical Application


The LT®3641 is a dual channel, current mode monolithic buck switching regulator with a power-on reset and a watchdog timer. Both regulators are synchronized to a single oscillator with an adjustable frequency (350kHz to 2.5MHz). At light loads, both regulators operate in low ripple Burst Mode® to maintain high effi ciency and low output ripple.

The high voltage channel is a nonsynchronous buck with an internal 2.4A top switch that operates from an input of 4V to 42V and input transient protection to 55V. The low voltage channel operates from an input of 2.5V to 5.5V. Internal synchronous power switches provide high effi ciency without the need of external Schottky diode. Both channels have cycle-by-cycle current limit, providing protection against shorted outputs.

The power-on reset and watchdog timeout periods are both adjustable using external capacitors. The window mode watchdog timer fl ags when the μP pulses group too close together or too far apart.

The LT3641 is available in a 28-pin 4mm × 5mm QFN package and 28-pin TSSOP package. Both packages have an exposed pad for low thermal resistance.


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

Part Number Package Code Temp Package
LT3641EFE#PBF TSSOP-28 FE E 05-08-1663 (EB) RoHS
LT3641EFE#TRPBF TSSOP-28 FE E 05-08-1663 (EB) RoHS
LT3641EUFD#PBF 4x5 QFN-28 UFD E 05-08-1712 RoHS
LT3641EUFD#TRPBF 4x5 QFN-28 UFD E 05-08-1712 RoHS
LT3641HFE#PBF TSSOP-28 FE H 05-08-1663 (EB) RoHS
LT3641HFE#TRPBF TSSOP-28 FE H 05-08-1663 (EB) RoHS
LT3641IFE#PBF TSSOP-28 FE I 05-08-1663 (EB) RoHS
LT3641IFE#TRPBF TSSOP-28 FE I 05-08-1663 (EB) RoHS
LT3641IUFD#PBF 4x5 QFN-28 UFD I 05-08-1712 RoHS
LT3641IUFD#TRPBF 4x5 QFN-28 UFD I 05-08-1712 RoHS

LT3641 Package Drawing
LT3641 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
LT3641EFE#PBF TSSOP-28 E $5.43 $3.80 Yes
LT3641EFE#TRPBF TSSOP-28 E $3.86 Yes
LT3641EUFD#PBF 4x5 QFN-28 E $5.22 $3.65 Yes
LT3641EUFD#TRPBF 4x5 QFN-28 E $3.71 Yes
LT3641HFE#PBF TSSOP-28 H $6.33 $4.43 Yes
LT3641HFE#TRPBF TSSOP-28 H $4.49 Yes
LT3641IFE#PBF TSSOP-28 I $5.97 $4.18 Yes
LT3641IFE#TRPBF TSSOP-28 I $4.24 Yes
LT3641IUFD#PBF 4x5 QFN-28 I $5.74 $4.02 Yes
LT3641IUFD#TRPBF 4x5 QFN-28 I $4.08 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
DC1727A LT3641EFE Demo Board I Power-On Reset and Watchdog Timer, 7V ≤ VIN ≤ 42V (55V Transients), Vout1 = 5V @ 1A, Vout2 = 1.8V @ 0.8A $125.00
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