LDL1117S33R

Product Overview

The LDL1117S33R from STMicroelectronics is a positive, fixed-output linear voltage regulator designed to provide a 3.3 V rail at up to 1.2 A. It is supplied in a surface-mount SOT-223 package, also identified as TO-261-4 or TO-261AA, and is intended for single-output power conversion in compact circuit boards. The device accepts a maximum input voltage of 18 V and specifies a maximum dropout voltage of 0.6 V at 1.2 A, making it suitable for applications where the regulator input must remain close to the regulated output. Its quiescent current is 500 µA, and its power supply rejection ratio is specified as 87 dB to 65 dB over 120 Hz to 100 kHz. Built-in protection features include over-current, over-temperature, and under-voltage lockout, while the junction temperature range is -40°C to 125°C.

Key Features

• Positive fixed single-output linear regulator providing a 3.3 V regulated output.
• Output current of 1.2 A with maximum dropout of 0.6 V at 1.2 A.
• Maximum input voltage of 18 V supports regulation from higher voltage supplies.
• Quiescent current of 500 µA and PSRR of 87 dB to 65 dB from 120 Hz to 100 kHz.
• Protection features include over-current, over-temperature, and under-voltage lockout (UVLO).
• Surface-mount SOT-223 package, TO-261-4 / TO-261AA, with junction temperature range of -40°C to 125°C.

Applications

• 3.3 V fixed-rail generation for digital logic, microcontroller boards, and embedded system power domains.
• Low-dropout regulation from intermediate or battery-derived supplies where input-to-output headroom is limited.
• Compact surface-mount power conversion in space-constrained boards using the SOT-223 package.

Design & Procurement Notes

Design the input network to stay below the 18 V maximum input rating while providing sufficient headroom above the 3.3 V output for the 0.6 V dropout at 1.2 A. The PSRR range, 87 dB to 65 dB over 120 Hz to 100 kHz, can guide input filtering when ripple is present at those frequencies. The 500 µA quiescent current should be considered in low-power rail calculations. Because the device includes over-current, over-temperature, and under-voltage lockout protection, verify that system start-up and fault handling are compatible with these functions. The SOT-223 package and junction temperature range of -40°C to 125°C require board layout and thermal design that keep the junction within this range. For procurement and bill-of-material consistency, specify the part number LDL1117S33R and the SOT-223 / TO-261-4 / TO-261AA package designation.