LT3651-4.X - Monolithic 4A High Voltage 1 Cell Li-Ion Battery Charger


  • Wide Input Voltage Range: Up to 32V (40V Absolute Maximum)
  • Programmable Charge Current Up to 4A
  • Selectable C/10 or Onboard Timer Termination
  • Dynamic Charge Rate Programming/Soft-Start
  • Programmable Input Current Limit
  • 0.5% Float Voltage Accuracy
  • 7.5% Charge Current Accuracy
  • 4% C/10 Detection Accuracy
  • NTC Resistor Temperature Monitor
  • Auto-Recharge at 97.5% Float Voltage
  • Auto-Precondition <70% Float Voltage
  • Bad Battery Detection with Auto-Reset
  • Average Current Mode, Synchronous Switcher
  • User Programmable Frequency
  • Low Profile (0.75mm) 5mm × 6mm 36-Pin QFN Package

Typical Application

LT3651-4.1 Typical Application
LT3651-4.1 Typical Application


The LT®3651 is a 1 cell 4A Li-Ion/Polymer battery charger that operates with input voltages up to 32V. An efficient monolithic average current mode synchronous switching regulator provides constant current, constant voltage charging with programmable maximum charge current. A charging cycle starts with battery insertion or when the battery voltage drops 2.5% below the float voltage. Charger termination is selectable as either charge current or internal safety timer timeout. Charge current termination occurs when the charge current falls to one-tenth the programmed maximum current (C/10). Timer based termination is typically set to three hours and is user programmable (charging continues below C/10 until timeout). Once charging is terminated, the LT3651 supply current drops to 85μA into a standby mode.

The LT3651 offers several safety features. A discharged battery is preconditioned with a small trickle charge and generates a signal if unresponsive. A thermistor monitors battery temperature, halting charging if out of range. Excessive die temperature reduces charge current. Charge current is also reduced to maintain constant input current to prevent excessive input loading.

The LT3651 is available in a 5mm × 6mm 36-pin QFN package.

 Float Voltage
LT3651-4.1 4.1V
LT3651-4.2 4.2V
LT3651-8.2 8.2V
LT3651-8.4 8.4V


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
LT3651EUHE-4.1#PBF 5x6 QFN-36 UHE E 05-08-1753 Yes
LT3651EUHE-4.1#TRPBF 5x6 QFN-36 UHE E 05-08-1753 Yes
LT3651EUHE-4.2#PBF 5x6 QFN-36 UHE E 05-08-1753 Yes
LT3651EUHE-4.2#TRPBF 5x6 QFN-36 UHE E 05-08-1753 Yes
LT3651IUHE-4.1#PBF 5x6 QFN-36 UHE I 05-08-1753 Yes
LT3651IUHE-4.1#TRPBF 5x6 QFN-36 UHE I 05-08-1753 Yes
LT3651IUHE-4.2#PBF 5x6 QFN-36 UHE I 05-08-1753 Yes
LT3651IUHE-4.2#TRPBF 5x6 QFN-36 UHE I 05-08-1753 Yes

LT3651-4.1 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
LT3651EUHE-4.1#PBF 5x6 QFN-36 E $5.90 $4.13 Yes
LT3651EUHE-4.1#TRPBF 5x6 QFN-36 E $4.19 Yes
LT3651EUHE-4.2#PBF 5x6 QFN-36 E $5.90 $4.13 Yes
LT3651EUHE-4.2#TRPBF 5x6 QFN-36 E $4.19 Yes
LT3651IUHE-4.1#PBF 5x6 QFN-36 I $6.79 $4.75 Yes
LT3651IUHE-4.1#TRPBF 5x6 QFN-36 I $4.81 Yes
LT3651IUHE-4.2#PBF 5x6 QFN-36 I $6.79 $4.75 Yes
LT3651IUHE-4.2#TRPBF 5x6 QFN-36 I $4.81 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
DC1362A-A LT3651EUHE-4.2 Demo Board | 6.5V ≤ VIN ≤ 32V, 4A Li-Ion Battery Charger, Vout = 4.2V @ 4A $150.00
DC1362A-B LT3651EUHE-4.1 Demo Board | 6.5V ≤ VIN ≤ 32V, 4A Li-Ion Battery Charger, Vout = 4.1V @ 4A $150.00
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Click here to view our complete list of demo boards


  • Industrial Handheld Instruments
  • 12V to 24V Automotive and Heavy Equipment
  • Desktop Cradle Chargers
  • Notebook Computers

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