LT3999 - Low Noise, 1A, 1MHz Push-Pull DC/DC Driver with Duty Cycle Control


  • Wide Input Operating Range: 2.7V to 36V
  • Dual 1A Switches with Programmable Current Limit
  • Programmable Switching Frequency: 50kHz to 1MHz
  • Frequency Synchronization Up to 1MHz
  • ΔVIN Compensation Using Duty Cycle Control
  • Low Noise Topology
  • Programmable Input Over and Undervoltage Lockout
  • Cross Conduction Prevention Circuitry
  • Programmable Soft-Start
  • Low Shutdown Current: <1μA
  • 10-Lead MSOP and DFN Packages

Typical Application

LT3999 Typical Application
LT3999 Typical Application


The LT®3999 is a monolithic, high voltage, high frequency DC/DC transformer driver providing isolated power in a small solution footprint.

The LT3999 has two 1A current limited power switches that switch out of phase. The duty cycle is programmable to adjust the output voltage. The switching frequency is programmed up to 1MHz and can be synchronized to an external clock for more accurate placement of switcher harmonics. The input operating range is programmed with the precision undervoltage and overvoltage lockouts. The supply current is reduced to less than 1μA during shutdown. A user-defined RC time constant provides an adjustable soft-start capability by limiting the inrush current at start-up.

The LT3999 is available in a 10-lead MSOP and 3mm × 3mm DFN package with exposed pad.


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
LT3999EDD#PBF 3x3 DFN-10 DD E 05-08-1699 Yes
LT3999EDD#TRPBF 3x3 DFN-10 DD E 05-08-1699 Yes
LT3999EMSE#PBF MS-10E MSE E 05-08-1664 Yes
LT3999EMSE#TRPBF MS-10E MSE E 05-08-1664 Yes
LT3999HMSE#PBF MS-10E MSE H 05-08-1664 Yes
LT3999HMSE#TRPBF MS-10E MSE H 05-08-1664 Yes
LT3999IDD#PBF 3x3 DFN-10 DD I 05-08-1699 Yes
LT3999IDD#TRPBF 3x3 DFN-10 DD I 05-08-1699 Yes
LT3999IMSE#PBF MS-10E MSE I 05-08-1664 Yes
LT3999IMSE#TRPBF MS-10E MSE I 05-08-1664 Yes
LT3999MPMSE#PBF MS-10E MSE MP 05-08-1664 Yes
LT3999MPMSE#TRPBF MS-10E MSE MP 05-08-1664 Yes

LT3999 Package Drawing
LT3999 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
LT3999EDD#PBF 3x3 DFN-10 E $3.93 $2.75 Yes
LT3999EDD#TRPBF 3x3 DFN-10 E $2.81 Yes
LT3999EMSE#PBF MS-10E E $3.93 $2.75 Yes
LT3999EMSE#TRPBF MS-10E E $2.81 Yes
LT3999HMSE#PBF MS-10E H $4.87 $3.41 Yes
LT3999HMSE#TRPBF MS-10E H $3.47 Yes
LT3999IDD#PBF 3x3 DFN-10 I $4.46 $3.12 Yes
LT3999IDD#TRPBF 3x3 DFN-10 I $3.18 Yes
LT3999IMSE#PBF MS-10E I $4.46 $3.12 Yes
LT3999IMSE#TRPBF MS-10E I $3.18 Yes
LT3999MPMSE#PBF MS-10E MP $12.02 $8.41 Yes
LT3999MPMSE#TRPBF MS-10E MP $8.47 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
DC2049A LT3999EMSE Isolated Demo Board | Dual Output Push-Pull Transformer Driver, 10V ≤ VIN ≤ 15.5V; VOUT = ±12V @ 0.2A $125.00
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Click here to view our complete list of demo boards


  • Low Noise Isolated Supplies
  • Medical Instrument and Safety
  • Distributed Power
  • Multiple Output Supplies
  • Positive-to-Negative Supplies
  • Noise Immunity in Data Acquisition, RS232 and RS485

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