Features and Benefits
- 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
- 16µA Quiescent Current in Shutdown
- Stable with 0.33µF Output Capacitor
- Reverse Battery Protection
- No Reverse Current with Input Low
- Thermal Limiting
- Available in the 8-Lead SO, 8-Lead PDIP, 3-Lead SOT-23 and 3-Lead TO-92 Packages
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.
- Low Current Regulator
- Regulator for Battery-Powered Systems
- Post Regulator for Switching Supplies
Markets and Technologies
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Documentation & Resources
R086 Reliability Data3/22/2018
AN67 - Linear Technology Magazine Circuit Collection, Volume III8/20/2007
AN60 - PCMCIA Card and Card Socket Power Management:8/20/2007
AN58 - 5V to 3.3V Converters for Microprocessor Systems8/20/2007
AN54 - Power Conversion from Milliamps to Amps at Ultra-High Efficiency (Up to 95%)8/20/2007
AN53 - Micropower High Side MOSFET Drivers8/20/2007
AN51 - Power Conditioning for Notebook and Palmtop Systems8/20/2007
AN-105: Current Sense Circuit Collection Making Sense of Current12/1/2005
DN96 - 12-Bit Rail-to-Rail Micropower DACs in an SO-87/8/2014
DN76 - PC Card Power Management Techniques4/1/2014
DN82 - 5V to 3.3V Regulator with Fail-Safe Switchover3/26/2014
DN210 - 2-Phase, Dual Switching Regulator Fits in Tight Places3/21/2014
DN78 - Triple Output 3.3V, 5V, and 12V High Efficiency Notebook Power Supply3/21/2014
DN91 - 5V to 3.3V Circuit Collection3/21/2014
Design Note 97: Flash Memory VPP Generator Reference Design2/1/1995
Design Note 74: Techniques for Deriving 3.3V from 5V Supplies9/1/1993
Three-Terminal Linear Regulator Evolution Continues Unabated2/19/2015
Wide Input Range, High Efficiency Step-Down Switching Regulators11/1/1998 LT Journal
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