LTC3550 - Dual Input USB/AC Adapter Li-Ion Battery Charger with 600mA Buck Converter


  • Charges Single-Cell Li-Ion Battery from Wall Adapter and USB Inputs
  • Automatic Input Power Detection and Selection
  • Charge Current Programmable Up to 950mA from Wall Adapter Input
  • Adjustable Output, High Efficiency 600mA Synchronous DC/DC Converter
  • No External MOSFET, Sense Resistor or Blocking Diode Needed
  • Thermal Regulation Maximizes Charge Rate Without Risk of Overheating
  • Preset Charge Voltage with ±0.6% Accuracy
  • Programmable Charge Current Termination
  • 1.5MHz Constant Frequency Operation (Step-Down Converter)
  • 18μA USB Suspend Current in Shutdown
  • “Power Present” Status Output
  • Charge Status Output
  • Automatic Recharge
  • Available in a Thermally Enhanced, Low Profile (0.75mm) 16-Lead (5mm × 3mm) DFN Package

Typical Application

LTC3550 Typical Application
LTC3550 Typical Application


The LTC3550 is a standalone linear charger with a 600mA monolithic synchronous buck converter. It is capable of charging a single-cell Li-Ion battery from both wall adapter and USB inputs. The charger automatically selects the appropriate power source for charging.

Internal thermal feedback regulates the battery charge current to maintain a constant die temperature during high power operation or high ambient temperature conditions. The float voltage is fixed at 4.2V and the charge currents are programmed with external resistors. The LTC3550 terminates the charge cycle when the charge current drops below the programmed termination threshold after the final float voltage is reached. With power applied to both inputs, the LTC3550 can be put into shutdown mode reducing the DCIN supply current to 20μA, the USBIN supply current to 10μA, and the battery drain current to less than 2μA.

The DC/DC converter switching frequency is internally set at 1.5MHz, allowing the use of small surface mount inductors and capacitors.

LTC3550 Adjustable 
LTC3550-1 1.875V


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
LTC3550EDHC#PBF 5x3 DFN-16 DHC E 05-08-1706 Yes
LTC3550EDHC#TRPBF 5x3 DFN-16 DHC E 05-08-1706 Yes

LTC3550 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
LTC3550EDHC#PBF 5x3 DFN-16 E $2.86 $2.00 Yes
LTC3550EDHC#TRPBF 5x3 DFN-16 E $2.06 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
DC1068A LTC3550EDHC | Dual Input USB/AC Adaptor Battery Charger and 600mA Synchronous Step-Down Converter $150.00
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Click here to view our complete list of demo boards


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