LDL1117S12R

The STMicroelectronics LDL1117S12R is a 1.2A high-PSRR low-dropout linear voltage regulator providing a fixed 1.2V output from an input voltage range of 2.6V to 18V. The 1.2V output is well-suited for modern low-voltage FPGA, CPLD, and microcontroller core supply requirements. With a typical dropout voltage of 350mV at 1.2A, it can regulate efficiently from low input voltages. The high PSRR of 87dB at 120Hz and greater than 40dB at 100kHz makes it ideal for cleaning noisy switch-mode supply outputs. The device includes internal current limit, safe operating area, and thermal shutdown protection. It is stable with ceramic output capacitors from 1uF to 100uF.

The LDL1117S12R operates as a series-pass linear voltage regulator with three key subsystems: 1) Reference and Error Amplifier: A bandgap voltage reference provides the stable reference voltage. The error amplifier compares a fraction of the output with this reference and drives the pass element to maintain regulation at 1.2V. 2) Pass Element: The internal NPN pass transistor provides the current path from VIN to VOUT with low dropout voltage. At 1.2A load, the typical dropout is 350mV. 3) Protection: Current limiting protects against short circuits, SOA protection ensures safe operation during transients, and thermal shutdown disables the output when the junction temperature exceeds the safe limit. The high PSRR is achieved through the internal bias generator and well-compensated error amplifier design.

• Low-voltage FPGA and CPLD core power supply regulation at 1.2V
• SMPS post-regulation for noise-sensitive low-voltage digital circuits
• Point-of-load 1.2V regulation on motherboards and embedded systems
• DC-DC converter secondary regulation with high PSRR requirements