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.
The LT1121 series are micropower low‑dropout (LDO) regulators with shutdown capability, offering up to 150 mA output current and a typical dropout voltage as low as 0.42 V at full load. Features include 30 pA quiescent current, reverse‑battery protection, and the ability to operate with very small output capacitors.
The devices are available in 8‑lead SO, 8‑lead PDIP, 3‑lead SOT‑23, 3‑lead TO‑92, and 3‑lead plastic packages. Typical performance curves, pin functions, and package dimensions are detailed, along with related parts for higher current or different voltage options.
| Maximum Output Current | 150 mA |
|---|---|
| Adjustable Output Voltage Range | 3.75 V to 30 V |
| Fixed Output Voltages | 3.3 V, 5 V |
| Shutdown Pin Input Voltage Range | up to 7 V |
Yes, the device is designed to withstand reverse input voltages and prevents reverse current flow.
The LT1121 is offered with fixed 3.3 V and 5 V output versions.