LTC3633A/LTC3633A-1 - Dual Channel 3A, 20V Monolithic Synchronous Step-Down Regulator


  • 3.6V to 20V Input Voltage Range
  • 3A Output Current per Channel
  • Up to 95% Efficiency
  • Low Duty Cycle Operation: 5% at 2.25MHz
  • Selectable 0°/180° Phase Shift Between Channels
  • Adjustable Switching Frequency: 500kHz to 4MHz
  • External Frequency Synchronization
  • Current Mode Operation for Excellent Line and Load Transient Response
  • 0.6V Reference Allows Low Output Voltages
  • User Selectable Burst Mode® Operation or Forced Continuous Mode Operation
  • Output Voltage Tracking and Soft-Start Capability
  • Short-Circuit Protected
  • Overvoltage Input and Overtemperature Protection
  • Power Good Status Outputs
  • LTC3633: 16V Absolute Maximum VIN
  • LTC3633A: 20V Absolute Maximum VIN, Pin Compatible with LTC3633
  • Low Profile (4mm × 5mm) QFN-28 and 28-Lead TSSOP Packages

Typical Application

LTC3633A Typical Application
LTC3633A Typical Application


The LTC®3633A is a high efficiency, dual-channel monolithic synchronous buck regulator using a controlled on-time, current mode architecture, with phase lockable switching frequency. The two channels can run 180° out of phase to relax the requirements for input and output capacitance. The operating supply voltage range is from 3.6V to 20V, making it suitable for lithium-ion battery stacks as well as point of load power supply applications from a 12V or 5V supply.

The operating frequency is programmable from 500kHz to 4MHz with an external resistor and may be synchronized to an external clock signal. The high frequency capability allows the use of small surface mount inductors and capacitors. The unique constant frequency/controlled ontime architecture is ideal for high step-down ratio applications that operate at high frequency while demanding fast transient response. An internal phase locked loop servos the on-time of the internal one-shot timer to match the frequency of the internal clock or an applied external clock.

The LTC3633A can select between forced continuous mode and high efficiency Burst Mode operation. The LTC3633A and LTC3633A-1 differ in their output voltage sense range (refer to Table 1 in the Operation section for a description of the entire LTC3633A product family).

Part NumberOutput Voltage Sense RangeSVin InputV2P5 OutputLTC3633 Pin Compatible
LTC3633A 0.6V TO 6V No Yes Yes
LTC3633A-1 1.5V TO 12V No Yes Yes
LTC3633A-2 0.6V TO 6V Yes No No
LTC3633A-3 1.5V TO 12V Yes No No


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
LTC3633AEFE-1#PBF TSSOP-28 FE E 05-08-1663 (EB) Yes
LTC3633AEFE-1#TRPBF TSSOP-28 FE E 05-08-1663 (EB) Yes
LTC3633AEFE#PBF TSSOP-28 FE E 05-08-1663 (EB) Yes
LTC3633AEFE#TRPBF TSSOP-28 FE E 05-08-1663 (EB) Yes
LTC3633AEUFD-1#PBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3633AEUFD-1#TRPBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3633AEUFD#PBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3633AEUFD#TRPBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3633AIFE-1#PBF TSSOP-28 FE I 05-08-1663 (EB) Yes
LTC3633AIFE-1#TRPBF TSSOP-28 FE I 05-08-1663 (EB) Yes
LTC3633AIFE#PBF TSSOP-28 FE I 05-08-1663 (EB) Yes
LTC3633AIFE#TRPBF TSSOP-28 FE I 05-08-1663 (EB) Yes
LTC3633AIUFD-1#PBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LTC3633AIUFD-1#TRPBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LTC3633AIUFD#PBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LTC3633AIUFD#TRPBF 4x5 QFN-28 UFD I 05-08-1712 Yes

LTC3633A Package Drawing
LTC3633A 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
LTC3633AEFE-1#PBF TSSOP-28 E $6.29 $4.40 Yes
LTC3633AEFE-1#TRPBF TSSOP-28 E $4.46 Yes
LTC3633AEFE#PBF TSSOP-28 E $6.29 $4.40 Yes
LTC3633AEFE#TRPBF TSSOP-28 E $4.46 Yes
LTC3633AEUFD-1#PBF 4x5 QFN-28 E $6.07 $4.25 Yes
LTC3633AEUFD-1#TRPBF 4x5 QFN-28 E $4.31 Yes
LTC3633AEUFD#PBF 4x5 QFN-28 E $6.07 $4.25 Yes
LTC3633AEUFD#TRPBF 4x5 QFN-28 E $4.31 Yes
LTC3633AIFE-1#PBF TSSOP-28 I $6.99 $4.89 Yes
LTC3633AIFE-1#TRPBF TSSOP-28 I $4.95 Yes
LTC3633AIFE#PBF TSSOP-28 I $6.99 $4.89 Yes
LTC3633AIFE#TRPBF TSSOP-28 I $4.95 Yes
LTC3633AIUFD-1#PBF 4x5 QFN-28 I $6.74 $4.72 Yes
LTC3633AIUFD-1#TRPBF 4x5 QFN-28 I $4.78 Yes
LTC3633AIUFD#PBF 4x5 QFN-28 I $6.74 $4.72 Yes
LTC3633AIUFD#TRPBF 4x5 QFN-28 I $4.78 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
DC1895A LTC3633AEUFD Demo Board | Dual Buck, 3.6V ≤ VIN ≤ 20V, Vout1 = 1.2V/1.5V1.8V @ 3A, Vout2 = 2.5V/3.3V/5V @ 3A $150.00
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  • Distributed Power Systems
  • Battery Powered Instruments
  • Point of Load Power Supplies

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