LT1121 - Micropower Low Dropout Regulators with Shutdown

Features

  • 0.4V Dropout Voltage
  • 150mA Output Current
  • 30µA Quiescent Current
  • No Protection Diodes Needed
  • Adjustable Output from 3.75V to 30V
  • 3.3V and 5V Fixed Output Voltages
  • Controlled Quiescent Current in Dropout
  • Shutdown
  • 16µA Quiescent Current in Shutdown
  • Stable with 0.33µF Output Capacitor
  • Reverse Battery Protection
  • No Reverse Current with Input Low
  • Thermal Limiting
Designed for Automotive and Transportation Applications
AEC-Q100 generic family data available for specific packages


Typical Application

LT1121 Typical Application
LT1121 Typical Application

Description

The LT1121/LT1121-3.3/LT1121-5 are micropower low dropout regulators with shutdown. These devices are capable of supplying 150mA of output current with a dropout voltage of 0.4V. Designed for use in battery-powered systems, the low quiescent current, 30µA operating and 16µA in shutdown, makes them an ideal choice. The quiescent current is well-controlled; it does not rise in dropout as it does with many other low dropout PNP regulators.

Other features of the LT1121/LT1121-3.3/LT1121-5 include the ability to operate with very small output capacitors. They are stable with only 0.33µF on the output while most older devices require between 1µF and 100µF for stability. Small ceramic capacitors can be used, enhancing manufacturability. Also the input may be connected to ground or a reverse voltage without reverse current flow from output to input. This makes the LT1121 series 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.

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
LT1121ACS8-3.3#PBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1121ACS8-3.3#TRPBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1121ACS8-5#PBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1121ACS8-5#TRPBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1121ACS8#PBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1121ACS8#TRPBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1121AHVCS8#PBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1121AHVCS8#TRPBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1121AHVIS8#PBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1121AHVIS8#TRPBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1121AIS8-3.3#PBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1121AIS8-3.3#TRPBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1121AIS8-5#PBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1121AIS8-5#TRPBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1121AIS8#PBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1121AIS8#TRPBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1121CN8-3.3#PBF N-8 N C 05-08-1510 (N8) Yes
LT1121CN8-5#PBF N-8 N C 05-08-1510 (N8) Yes
LT1121CN8#PBF N-8 N C 05-08-1510 (N8) Yes
LT1121CS8-3.3#PBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1121CS8-3.3#TRPBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1121CS8-5#PBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1121CS8-5#TRPBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1121CS8#PBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1121CS8#TRPBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1121CST-3.3#PBF SOT-223 ST C 05-08-1630 Yes
LT1121CST-3.3#TRPBF SOT-223 ST C 05-08-1630 Yes
LT1121CST-5#PBF SOT-223 ST C 05-08-1630 Yes
LT1121CST-5#TRPBF SOT-223 ST C 05-08-1630 Yes
LT1121CZ-3.3#PBF TO-92 Z C 05-08-1410 Yes
LT1121CZ-3.3#TRPBF TO-92 Z C 05-08-1410 Yes
LT1121CZ-5#PBF TO-92 Z C 05-08-1410 Yes
LT1121CZ-5#TRPBF TO-92 Z C 05-08-1410 Yes
LT1121HVCS8#PBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1121HVCS8#TRPBF SO-8 S8 C 05-08-1610 (S8) Yes
LT1121HVIS8#PBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1121HVIS8#TRPBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1121IN8-3.3#PBF N-8 N I 05-08-1510 (N8) Yes
LT1121IN8-5#PBF N-8 N I 05-08-1510 (N8) Yes
LT1121IN8#PBF N-8 N I 05-08-1510 (N8) Yes
LT1121IS8-3.3#PBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1121IS8-3.3#TRPBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1121IS8-5#PBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1121IS8-5#TRPBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1121IS8#PBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1121IS8#TRPBF SO-8 S8 I 05-08-1610 (S8) Yes
LT1121IST-3.3#PBF SOT-223 ST I 05-08-1630 Yes
LT1121IST-3.3#TRPBF SOT-223 ST I 05-08-1630 Yes
LT1121IST-5#PBF SOT-223 ST I 05-08-1630 Yes
LT1121IST-5#TRPBF SOT-223 ST I 05-08-1630 Yes
LT1121IZ-3.3#PBF TO-92 Z I 05-08-1410 Yes
LT1121IZ-3.3#TRPBF TO-92 Z I 05-08-1410 Yes
LT1121IZ-5#PBF TO-92 Z I 05-08-1410 Yes
LT1121IZ-5#TRPBF TO-92 Z I 05-08-1410 Yes


LT1121 Package Drawing
LT1121 Package Drawing
LT1121 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
LT1121ACS8-3.3#PBF SO-8 C $2.50 $1.95 Yes
LT1121ACS8-3.3#TRPBF SO-8 C $2.01 Yes
LT1121ACS8-5#PBF SO-8 C $2.50 $1.95 Yes
LT1121ACS8-5#TRPBF SO-8 C $2.01 Yes
LT1121ACS8#PBF SO-8 C $2.50 $1.95 Yes
LT1121ACS8#TRPBF SO-8 C $2.01 Yes
LT1121AHVCS8#PBF SO-8 C $2.78 $2.35 Yes
LT1121AHVCS8#TRPBF SO-8 C $2.42 Yes
LT1121AHVIS8#PBF SO-8 I $3.26 $2.75 Yes
LT1121AHVIS8#TRPBF SO-8 I $2.81 Yes
LT1121AIS8-3.3#PBF SO-8 I $2.92 $2.30 Yes
LT1121AIS8-3.3#TRPBF SO-8 I $2.36 Yes
LT1121AIS8-5#PBF SO-8 I $2.92 $2.30 Yes
LT1121AIS8-5#TRPBF SO-8 I $2.36 Yes
LT1121AIS8#PBF SO-8 I $2.92 $2.30 Yes
LT1121AIS8#TRPBF SO-8 I $2.36 Yes
LT1121CN8-3.3#PBF N-8 C $1.83 $1.50 Yes
LT1121CN8-5#PBF N-8 C $1.83 $1.50 Yes
LT1121CN8#PBF N-8 C $1.83 $1.50 Yes
LT1121CS8-3.3#PBF SO-8 C $2.00 $1.60 Yes
LT1121CS8-3.3#TRPBF SO-8 C $1.66 Yes
LT1121CS8-5#PBF SO-8 C $2.00 $1.60 Yes
LT1121CS8-5#TRPBF SO-8 C $1.66 Yes
LT1121CS8#PBF SO-8 C $2.00 $1.60 Yes
LT1121CS8#TRPBF SO-8 C $1.66 Yes
LT1121CST-3.3#PBF SOT-223 C $2.17 $1.70 Yes
LT1121CST-3.3#TRPBF SOT-223 C $1.76 Yes
LT1121CST-5#PBF SOT-223 C $2.17 $1.70 Yes
LT1121CST-5#TRPBF SOT-223 C $1.76 Yes
LT1121CZ-3.3#PBF TO-92 C $1.58 $1.30 Yes
LT1121CZ-3.3#TRPBF TO-92 C $1.36 Yes
LT1121CZ-5#PBF TO-92 C $1.58 $1.30 Yes
LT1121CZ-5#TRPBF TO-92 C $1.36 Yes
LT1121HVCS8#PBF SO-8 C $2.25 $1.90 Yes
LT1121HVCS8#TRPBF SO-8 C $1.96 Yes
LT1121HVIS8#PBF SO-8 I $2.78 $2.35 Yes
LT1121HVIS8#TRPBF SO-8 I $2.41 Yes
LT1121IN8-3.3#PBF N-8 I $2.17 $1.80 Yes
LT1121IN8-5#PBF N-8 I $2.17 $1.80 Yes
LT1121IN8#PBF N-8 I $2.17 $1.80 Yes
LT1121IS8-3.3#PBF SO-8 I $2.42 $1.95 Yes
LT1121IS8-3.3#TRPBF SO-8 I $2.01 Yes
LT1121IS8-5#PBF SO-8 I $2.42 $1.95 Yes
LT1121IS8-5#TRPBF SO-8 I $2.01 Yes
LT1121IS8#PBF SO-8 I $2.42 $1.95 Yes
LT1121IS8#TRPBF SO-8 I $2.01 Yes
LT1121IST-3.3#PBF SOT-223 I $2.58 $2.05 Yes
LT1121IST-3.3#TRPBF SOT-223 I $2.11 Yes
LT1121IST-5#PBF SOT-223 I $2.58 $2.05 Yes
LT1121IST-5#TRPBF SOT-223 I $2.11 Yes
LT1121IZ-3.3#PBF TO-92 I $1.92 $1.55 Yes
LT1121IZ-3.3#TRPBF TO-92 I $1.61 Yes
LT1121IZ-5#PBF TO-92 I $1.92 $1.55 Yes
LT1121IZ-5#TRPBF TO-92 I $1.61 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

Please contact your local sales representative for more information regarding reliability reports and AEC-Q100 data 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
LT1121HVIS8#PBF SO-8 I $2.78 $2.35 Yes
LT1121HVIS8#TRPBF SO-8 I $2.41 Yes
LT1121IST-3.3#PBF SOT-223 I $2.58 $2.05 Yes
LT1121IST-3.3#TRPBF SOT-223 I $2.11 Yes
LT1121IST-5#PBF SOT-223 I $2.58 $2.05 Yes
LT1121IST-5#TRPBF SOT-223 I $2.11 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

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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:
LT1121
LT1121-3.3
LT1121-5

Technical Support