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
AEC-Q100 data available for specific packages
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 |
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
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 | |
|---|---|---|---|---|---|---|
| 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 Now • Request Samples | ||||||
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
- For immediate technical assistance, contact your local sales office or distributor or call 1-800-4-LINEAR (US customers only) or 408-432-1900.
- For less urgent requests, please complete our Technical Support Request Form. Please allow 2-3 business days for reply.
