LTC3520 - Synchronous 1A Buck-Boost and 600mA Buck Converters


  • Dual High Efficiency DC/DC Converters:
    Buck-Boost (VOUT: 2.2V to 5.25V, IOUT = 1A at
    VOUT = 3.3V, VIN ≥ 3V)
    Buck (VOUT: 0.8V to VIN, IOUT = 600mA)
  • 2.2V to 5.5V Input Voltage Range
  • Pin-Selectable Burst Mode® Operation
  • Uncommitted Gain Block for LDO Controller, Battery Good Indication or Sequencing
  • Programmable 100kHz to 2MHz Switching Frequency
  • 55μA Total Quiescent Current for Both Converters in Burst Mode Operation
  • Thermal and Overcurrent Protection
  • <1μA Quiescent Current in Shutdown
  • 24-Lead 4mm × 4mm QFN Package

Typical Application

LTC3520 Typical Application
LTC3520 Typical Application


The LTC3520 combines 1A buck-boost and 600mA synchronous buck DC/DC converters in a tiny 4mm x 4mm package. A programmable switching frequency allows the efficiency to be optimized while minimizing the solution footprint. Both converters feature soft-start and current limit protection. The uncommitted gain block can be configured as an LDO or utilized as a battery-good comparator.

The buck converter is current mode controlled with internal synchronous rectification to improve efficiency. Pin-select- able Burst Mode operation can be enabled to improve light load efficiency, or the buck converter can be operated in low noise PWM mode for sensitive applications.

The buck-boost converter provides continuous conduction operation to maximize efficiency and minimize noise. At light loads, use of Burst Mode operation will improve efficiency.

The LTC3520 provides a <1µA shutdown mode and over- temperature shutdown on both converters. The LTC3520 is available in a low profile (0.75mm) 24-lead 4mm x 4mm QFN package.


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
LTC3520EUF#PBF 4x4 QFN-24 UF E 05-08-1697 Yes
LTC3520EUF#TRPBF 4x4 QFN-24 UF E 05-08-1697 Yes
LTC3520IUF#PBF 4x4 QFN-24 UF I 05-08-1697 Yes
LTC3520IUF#TRPBF 4x4 QFN-24 UF I 05-08-1697 Yes

LTC3520 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
LTC3520EUF#PBF 4x4 QFN-24 E $5.00 $3.50 Yes
LTC3520EUF#TRPBF 4x4 QFN-24 E $3.56 Yes
LTC3520IUF#PBF 4x4 QFN-24 I $5.76 $4.03 Yes
LTC3520IUF#TRPBF 4x4 QFN-24 I $4.09 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
DC1062A LTC3520EUF| Buck-Boost w/ 400mA Buck, Vin = 2.2V to 5.5V, Vout1 = 3.3V @ 1A (BB), Vout2 = 1.8V @ 0.6A, Vout3 (LDO Post Regulator) = 1.5V @ 200mA $125.00
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