LTC3634 - 15V Dual 3A Monolithic Step-Down Regulator for DDR Power


  • 3.6V to 15V Input Voltage Range
  • ±3A Output Current per Channel
  • Up to 95% Efficiency
  • Selectable 90°/180° Phase Shift Between Channels
  • Adjustable Switching Frequency: 500kHz to 4MHz
  • VTTR = VDDQ/2 = VTT Reference
  • ±1.6% Accurate VTTR at 0.75V
  • Optimal VOUT Range: 0.6V to 3V
  • ±10mA Buffered Output Supplies VREF Reference Voltage
  • Current Mode Operation for Excellent Line and Load Transient Response
  • External Clock Synchronization
  • Short-Circuit Protected
  • Input Overvoltage and Overtemperature Protection
  • Power Good Status Outputs
  • Available in (4mm × 5mm) QFN-28 and Thermally Enhanced 28-Lead TSSOP Packages

Typical Application

LTC3634 Typical Application
LTC3634 Typical Application


The LTC®3634 is a high efficiency, dual-channel monolithic synchronous step-down regulator which provides power supply and bus termination rails for DDR1, DDR2, and DDR3 SDRAM controllers. The operating input voltage range is 3.6V to 15V, making it suitable for point-of-load power supply applications from a 5V or 12V input, as well as various battery powered systems.

The VTT regulated output voltage is equal to VDDQIN• 0.5. An on-chip buffer capable of driving a 10mA load provides a low noise reference output (VTTR) also equal to VDDQIN• 0.5.

The operating frequency is programmable and synchronizable from 500kHz to 4MHz with an external resistor. The two channels can operate 180° out-of-phase, which relaxes the requirements for input and output capacitance. The unique controlled on-time architecture is ideal for powering DDR applications from a 12V supply at high switching frequencies, allowing the use of smaller external components.

The LTC3634 is offered in both 28-pin 4mm × 5mm QFN and 28-pin exposed pad TSSOP packages.


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
LTC3634EFE#PBF TSSOP-28 FE E 05-08-1663 (EB) Yes
LTC3634EFE#TRPBF TSSOP-28 FE E 05-08-1663 (EB) Yes
LTC3634EUFD#PBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3634EUFD#TRPBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3634HFE#PBF TSSOP-28 FE H 05-08-1663 (EB) Yes
LTC3634HFE#TRPBF TSSOP-28 FE H 05-08-1663 (EB) Yes
LTC3634HUFD#PBF 4x5 QFN-28 UFD H 05-08-1712 Yes
LTC3634HUFD#TRPBF 4x5 QFN-28 UFD H 05-08-1712 Yes
LTC3634IFE#PBF TSSOP-28 FE I 05-08-1663 (EB) Yes
LTC3634IFE#TRPBF TSSOP-28 FE I 05-08-1663 (EB) Yes
LTC3634IUFD#PBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LTC3634IUFD#TRPBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LTC3634MPFE#PBF TSSOP-28 FE MP 05-08-1663 (EB) Yes
LTC3634MPFE#TRPBF TSSOP-28 FE MP 05-08-1663 (EB) Yes
LTC3634MPUFD#PBF 4x5 QFN-28 UFD MP 05-08-1712 Yes
LTC3634MPUFD#TRPBF 4x5 QFN-28 UFD MP 05-08-1712 Yes

LTC3634 Package Drawing
LTC3634 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
LTC3634EFE#PBF TSSOP-28 E $6.29 $4.40 Yes
LTC3634EFE#TRPBF TSSOP-28 E $4.46 Yes
LTC3634EUFD#PBF 4x5 QFN-28 E $6.07 $4.25 Yes
LTC3634EUFD#TRPBF 4x5 QFN-28 E $4.31 Yes
LTC3634HFE#PBF TSSOP-28 H $7.34 $5.14 Yes
LTC3634HFE#TRPBF TSSOP-28 H $5.20 Yes
LTC3634HUFD#PBF 4x5 QFN-28 H $7.10 $4.97 Yes
LTC3634HUFD#TRPBF 4x5 QFN-28 H $5.03 Yes
LTC3634IFE#PBF TSSOP-28 I $6.99 $4.89 Yes
LTC3634IFE#TRPBF TSSOP-28 I $4.95 Yes
LTC3634IUFD#PBF 4x5 QFN-28 I $6.74 $4.72 Yes
LTC3634IUFD#TRPBF 4x5 QFN-28 I $4.78 Yes
LTC3634MPFE#PBF TSSOP-28 MP $18.86 $13.20 Yes
LTC3634MPFE#TRPBF TSSOP-28 MP $13.26 Yes
LTC3634MPUFD#PBF 4x5 QFN-28 MP $18.22 $12.75 Yes
LTC3634MPUFD#TRPBF 4x5 QFN-28 MP $12.81 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
DC1708A LTC3634EUFD Demo Board (QFN) | VIN= 3.6V to 15V, VOUT1 =1.5V/1.8V/2.5V@±3A, VOUT2 = 0.5VIN (VTT)@±3A, VOUT3 = 0.5VIN (VTTR)@±10mA $150.00
DC1839A LTC3634EFE Demo Board (TSSOP) | VIN= 3.6V to 15V, VOUT1 =1.5V/1.8V/2.5V @ ±3A, VOUT2 =0.5VIN (VTT) @ ±3A, VOUT3 = 0.5VIN (VTTR) @ ±10mA $150.00
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  • DDR Memory Power Supplies

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Design Tools


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Models for the following parts are available in LTspice:


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