LTC3544 - Quad Synchronous Step-Down Regulator: 2.25MHz, 300mA, 200mA, 200mA, 100mA


  • High Efficiency: Up to 95%
  • Four Independent Regulators Provide Up to 300mA, 200mA, 200mA and 100mA Output Current
  • 2.25V to 5.5V Input Voltage Range
  • 2.25MHz Constant-Frequency Operation
  • No Schottky Diodes Required
  • Extremely Low Channel-to-Channel Transient Crosstalk
  • Low Ripple (20mVP-P) Burst Mode Operation:
    IQ = 70µA (All Channels On)
  • 0.8V Reference Allows Low Output Voltages
  • Shutdown Mode Draws <1µA Supply Current
  • Current Mode Operation for Excellent Line and Load Transient Response
  • Overtemperature Protected
  • Low Profile (3mm × 3mm) 16-Lead QFN Package

Typical Application

LTC3544 Typical Application
LTC3544 Typical Application


The LTC3544 is a quad, high efficiency, monolithic synchronous buck regulator using a constant-frequency, current mode architecture. The four regulators operate independently with separate run pins. The 2.25V to 5.5V input voltage range makes the LTC3544 well suited for single Li-Ion/polymer battery-powered applications. 100% duty cycle provides low dropout operation, extending battery runtime in portable systems. Low ripple Burst Mode® operation increases efficiency at light loads, further extending battery runtime with typically only 20mV of ripple.

Switching frequency is internally set to 2.25MHz, allowing the use of small surface mount inductors and capacitors. The internal synchronous switches increase efficiency and eliminate the need for external Schottky diodes. Low output voltages are easily supported with the 0.8V feedback reference voltage.

The LTC3544 is available in a low profile (0.75mm) (3mm × 3mm) QFN package.

  Light Load Operation 
LTC3544 Burst Mode (20mVpp), < 70uA Iq
LTC3544B Pulse Skip Mode


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
LTC3544EUD#PBF 3x3 QFN-16 UD E 05-08-1691 Yes
LTC3544EUD#TRPBF 3x3 QFN-16 UD E 05-08-1691 Yes

LTC3544 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
LTC3544EUD#PBF 3x3 QFN-16 E $4.21 $2.95 Yes
LTC3544EUD#TRPBF 3x3 QFN-16 E $3.01 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
DC1040A-A LTC3544EUD Demo Board | Quad Sync Buck, 2.25V ≤ VIN ≤ 5.5V, Iout = 100mA, 200mA(x2) & 300mA Contact Factory
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Click here to view our complete list of demo boards


  • Cellular Telephones
  • Personal Information Appliances
  • Wireless and DSL Modems
  • Digital Still Cameras
  • Media Players
  • Portable Instruments

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Design Tools


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