LT1129 - Micropower Low Dropout Regulators with Shutdown

Features

  • 400mV Dropout Voltage
  • 700mA Output Current
  • 50μA Quiescent Current
  • No Protection Diodes Needed
  • Adjustable Output from 3.8V to 30V
  • 3.3V and 5V Fixed Output Voltages
  • Controlled Quiescent Current in Dropout
  • Shutdown
  • 16μA Quiescent Current in Shutdown
  • Stable with 3.3μF Output Capacitor
  • Reverse Battery Protection
  • No Reverse Output Current
  • Thermal Limiting
  • Surface Mount SOT-223 and DD-Pak Packages
Designed for Automotive and Transportation Applications
AEC-Q100 data available for specific packages


Typical Application

LT1129 Typical Application
LT1129 Typical Application

Description

The LT1129/LT1129-3.3/LT1129-5 are micropower low dropout regulators with shutdown. The devices are capable of supplying 700mA of output current with a dropout voltage of 400mV at maximum output. Designed for use in battery-powered systems, the low quiescent current, 50μA operating and 16μA in shutdown, make them an ideal choice. The quiescent current does not rise in dropout as it does with many other low dropout PNP regulators.

Other features of the LT1129 /LT1129-3.3/LT1129-5 include the ability to operate with small output capacitors. They are stable with only 3.3μF on the output while most older devices require between 10μF and 100μF for stability. Also the input may be connected to ground or a reverse voltage without reverse current flow from output to input. This makes the LT1129/LT1129-3.3/LT1129-5 ideal for backup power situations where the output is held high and the input is at ground or reversed. Under these conditions, only 16μA will flow from the output pin to ground. The devices are available in 5-lead TO-220, 5-lead DD-Pak and 3-lead SOT-223 packages.

Packaging

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
Drawing
RoHS
LT1129CQ-3.3#PBF DDPAK-5 Q C 05-08-1461 Yes
LT1129CQ-3.3#TRPBF DDPAK-5 Q C 05-08-1461 Yes
LT1129CQ-5#PBF DDPAK-5 Q C 05-08-1461 Yes
LT1129CQ-5#TRPBF DDPAK-5 Q C 05-08-1461 Yes
LT1129CQ#PBF DDPAK-5 Q C 05-08-1461 Yes
LT1129CQ#TRPBF DDPAK-5 Q C 05-08-1461 Yes
LT1129CS8-3.3#PBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1129CS8-3.3#TRPBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1129CS8-5#PBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1129CS8-5#TRPBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1129CS8#PBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1129CS8#TRPBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1129CST-3.3#PBF SOT-223 ST C 05-08-1630 Yes
LT1129CST-3.3#TRPBF SOT-223 ST C 05-08-1630 Yes
LT1129CST-5#PBF SOT-223 ST C 05-08-1630 Yes
LT1129CST-5#TRPBF SOT-223 ST C 05-08-1630 Yes
LT1129CT-3.3#06PBF TO-220 T C 05-08-1421 (Flow 06) Yes
LT1129CT-3.3#PBF TO-220 T C 05-08-1421 (Standard) Yes
LT1129CT-5#06PBF TO-220 T C 05-08-1421 (Flow 06) Yes
LT1129CT-5#PBF TO-220 T C 05-08-1421 (Standard) Yes
LT1129CT#PBF TO-220 T C 05-08-1421 (Standard) Yes
LT1129IQ-3.3#PBF DDPAK-5 Q I 05-08-1461 Yes
LT1129IQ-3.3#TRPBF DDPAK-5 Q I 05-08-1461 Yes
LT1129IQ-5#PBF DDPAK-5 Q I 05-08-1461 Yes
LT1129IQ-5#TRPBF DDPAK-5 Q I 05-08-1461 Yes
LT1129IQ#PBF DDPAK-5 Q I 05-08-1461 Yes
LT1129IQ#TRPBF DDPAK-5 Q I 05-08-1461 Yes
LT1129IS8-3.3#PBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1129IS8-3.3#TRPBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1129IS8-5#PBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1129IS8-5#TRPBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1129IS8#PBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1129IS8#TRPBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1129IST-3.3#PBF SOT-223 ST I 05-08-1630 Yes
LT1129IST-3.3#TRPBF SOT-223 ST I 05-08-1630 Yes
LT1129IST-5#PBF SOT-223 ST I 05-08-1630 Yes
LT1129IST-5#TRPBF SOT-223 ST I 05-08-1630 Yes
LT1129IT-3.3#PBF TO-220 T I 05-08-1421 (Standard) Yes
LT1129IT-5#06PBF TO-220 T I 05-08-1421 (Standard) Yes
LT1129IT-5#PBF TO-220 T I 05-08-1421 (Standard) Yes
LT1129IT#06PBF TO-220 T I 05-08-1421 (Flow 06) Yes
LT1129IT#PBF TO-220 T I 05-08-1421 (Standard) Yes
LT1129MPST-3.3 SOT-223 ST MP 05-08-1630 No
LT1129MPST-3.3#PBF SOT-223 ST MP 05-08-1630 Yes
LT1129MPST-3.3#TR SOT-223 ST MP 05-08-1630 No
LT1129MPST-3.3#TRPBF SOT-223 ST MP 05-08-1630 Yes


LT1129 Package Drawing
LT1129 Package Drawing
LT1129 Package Drawing
LT1129 Package Drawing
LT1129 Package Drawing
LT1129 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
(1-99)
Price
(1k)*
RoHS
LT1129CQ-3.3#PBF DDPAK-5 C $3.08 $2.45 Yes
LT1129CQ-3.3#TRPBF DDPAK-5 C $2.57 Yes
LT1129CQ-5#PBF DDPAK-5 C $3.08 $2.45 Yes
LT1129CQ-5#TRPBF DDPAK-5 C $2.57 Yes
LT1129CQ#PBF DDPAK-5 C $3.08 $2.45 Yes
LT1129CQ#TRPBF DDPAK-5 C $2.57 Yes
LT1129CS8-3.3#PBF SO-8 C $3.17 $2.50 Yes
LT1129CS8-3.3#TRPBF SO-8 C $2.56 Yes
LT1129CS8-5#PBF SO-8 C $3.17 $2.50 Yes
LT1129CS8-5#TRPBF SO-8 C $2.56 Yes
LT1129CS8#PBF SO-8 C $3.17 $2.50 Yes
LT1129CS8#TRPBF SO-8 C $2.56 Yes
LT1129CST-3.3#PBF SOT-223 C $2.83 $2.30 Yes
LT1129CST-3.3#TRPBF SOT-223 C $2.36 Yes
LT1129CST-5#PBF SOT-223 C $2.83 $2.30 Yes
LT1129CST-5#TRPBF SOT-223 C $2.36 Yes
LT1129CT-3.3#06PBF TO-220 C $2.67 $2.15 Yes
LT1129CT-3.3#PBF TO-220 C $2.67 $2.15 Yes
LT1129CT-5#06PBF TO-220 C $2.67 $2.15 Yes
LT1129CT-5#PBF TO-220 C $2.67 $2.15 Yes
LT1129CT#PBF TO-220 C $2.67 $2.15 Yes
LT1129IQ-3.3#PBF DDPAK-5 I $3.67 $2.95 Yes
LT1129IQ-3.3#TRPBF DDPAK-5 I $3.07 Yes
LT1129IQ-5#PBF DDPAK-5 I $3.67 $2.95 Yes
LT1129IQ-5#TRPBF DDPAK-5 I $3.07 Yes
LT1129IQ#PBF DDPAK-5 I $3.67 $2.95 Yes
LT1129IQ#TRPBF DDPAK-5 I $3.07 Yes
LT1129IS8-3.3#PBF SO-8 I $3.75 $2.95 Yes
LT1129IS8-3.3#TRPBF SO-8 I $3.01 Yes
LT1129IS8-5#PBF SO-8 I $3.75 $2.95 Yes
LT1129IS8-5#TRPBF SO-8 I $3.01 Yes
LT1129IS8#PBF SO-8 I $3.75 $2.95 Yes
LT1129IS8#TRPBF SO-8 I $3.01 Yes
LT1129IST-3.3#PBF SOT-223 I $3.17 $2.60 Yes
LT1129IST-3.3#TRPBF SOT-223 I $2.66 Yes
LT1129IST-5#PBF SOT-223 I $3.17 $2.60 Yes
LT1129IST-5#TRPBF SOT-223 I $2.66 Yes
LT1129IT-3.3#PBF TO-220 I $3.17 $2.60 Yes
LT1129IT-5#06PBF TO-220 I $3.17 $2.60 Yes
LT1129IT-5#PBF TO-220 I $3.17 $2.60 Yes
LT1129IT#06PBF TO-220 I $3.17 $2.60 Yes
LT1129IT#PBF TO-220 I $3.17 $2.60 Yes
LT1129MPST-3.3 SOT-223 MP $10.03 $7.02 No
LT1129MPST-3.3#PBF SOT-223 MP $10.03 $7.02 Yes
LT1129MPST-3.3#TR SOT-223 MP $7.08 No
LT1129MPST-3.3#TRPBF SOT-223 MP $7.08 Yes
Buy NowRequest Samples
* 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.

Click here to view our complete list of demo boards

Designed for Automotive and Transportation Applications

AEC-Q100 data is available for these specific part numbers. Please contact your local sales representative for more information regarding reliability reports or to inquire about parts that are not included. For more information, view our Automotive and Transportation page

Part Number Package Temp Price
(1-99)
Price
(1k)*
RoHS
LT1129IST-3.3#PBF SOT-223 I $3.17 $2.60 Yes
LT1129IST-3.3#TRPBF SOT-223 I $2.66 Yes
LT1129IST-5#PBF SOT-223 I $3.17 $2.60 Yes
LT1129IST-5#TRPBF SOT-223 I $2.66 Yes
LT1129MPST-3.3#PBF SOT-223 MP $10.03 $7.02 Yes
LT1129MPST-3.3#TRPBF SOT-223 MP $7.08 Yes
Buy NowRequest Samples
* 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.

Applications

  • Low Current Regulator
  • Regulator for Battery-Powered Systems
  • Post Regulator for Switching Supplies
  • 5V to 3.3V Logic Regulator

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Design Tools

LTspice

LTspice® software is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. Click here to download LTspice

To launch a ready to run LTspice demonstration circuit for this part:

  • Step 1: If you have not installed LTspice on this computer, download and install LTspice
  • Step 2: Once LTspice is installed, click on the link(s) below to launch the simulation
  • Step 3: If LTspice does not automatically open after clicking the link above, you can instead run the simulation by right clicking on the link and selecting "Save Target As." After saving the file to your computer, start LTspice and open the demonstration circuit by selecting 'Open' from the 'File' menu

To explore other ready to run LTspice demonstration circuits, please visit our Demo Circuits Collection.

Models for the following parts are available in LTspice:
LT1129
LT1129-3.3
LT1129-5

Technical Support