LT1959 - 4.5A, 500kHz Step-Down Switching Regulator


  • Operates with Input as Low as 4V
  • Output Range Down to 1.21V
  • Constant 500kHz Switching Frequency
  • Uses All Surface Mount Components
  • Inductor Size Reduced to 1.8µH
  • Saturating Switch Design: 0.07 Ohms
  • Shutdown Current: 20µA
  • Easily Synchronizable
  • Cycle-by-Cycle Current Limiting
  • 4.5A Switch
  • Current Mode Control

Typical Application

LT1959 Typical Application
LT1959 Typical Application


The LT1959 is a 500kHz monolithic buck mode switching regulator functionally identical to the LT1506 but optimized for lower output voltage applications. It will operate down to 1.21V output compared to 2.42V for the LT1506. A 4.5A switch is included on the die along with all the necessary oscillator, control and logic circuitry. High switching frequency allows a considerable reduction in the size of external components. The topology is current mode for fast transient response and good loop stability.

A special high speed bipolar process and new design techniques achieve high efficiency at high switching frequency. Efficiency is maintained over a wide output current range by keeping quiescent supply current to 4mA and by utilizing a supply boost capacitor to saturate the power switch.

The LT1959 fits into standard 7-pin DD and fused lead SO-8 packages. Full cycle-by-cycle short-circuit protection and thermal shutdown are provided. Standard surface mount external parts are used, including the inductor and capacitors. There is the optional function of shutdown or synchronization. A shutdown signal reduces supply current to 20µA. Synchronization allows an external logic level signal to increase the internal oscillator from 580kHz to 1MHz.


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
LT1959CR#PBF DDPAK-7 R C 05-08-1462 Yes
LT1959CR#TRPBF DDPAK-7 R C 05-08-1462 Yes
LT1959CS8#PBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1959CS8#TRPBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1959IR#PBF DDPAK-7 R I 05-08-1462 Yes
LT1959IR#TRPBF DDPAK-7 R I 05-08-1462 Yes
LT1959IS8#PBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1959IS8#TRPBF SO-8 S8 I 05-08-1610 (S8) Yes

LT1959 Package Drawing
LT1959 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
LT1959CR#PBF DDPAK-7 C $5.61 $4.74 Yes
LT1959CR#TRPBF DDPAK-7 C $4.86 Yes
LT1959CS8#PBF SO-8 C $5.19 $4.39 Yes
LT1959CS8#TRPBF SO-8 C $4.45 Yes
LT1959IR#PBF DDPAK-7 I $6.39 $5.40 Yes
LT1959IR#TRPBF DDPAK-7 I $5.52 Yes
LT1959IS8#PBF SO-8 I $5.98 $5.05 Yes
LT1959IS8#TRPBF SO-8 I $5.11 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
DC355A LT1959CS8 | 4.5A Switch, 500kHz Step-Down Regulator, 5V to 15Vin, 1.8Vout @ 4A $150.00
DC356A LT1959CR | 4.5A Switch, 500kHz Step-Down Regulator, 5V to 15Vin, 1.8Vout @ 4A $150.00
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  • Portable Computers
  • Battery-Powered Systems
  • Battery Chargers
  • Distributed Power
  • 5V to 3.3V Conversion
  • 5V to 2.5V Conversion
  • 5V to 1.8V Conversion

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