Fixed 1.2V rail with 75dB ripple rejection
The LD1117DT12CTR is a 1.2V fixed-output LDO from STMicroelectronics, rated for 800mA continuous output current. Its 75dB PSRR at 120Hz means the output ripple is attenuated by a factor of ~5600 relative to the input — useful for powering analog front-ends, ADC/DAC reference buffers, or sensor rails where switching-regulator noise would corrupt the signal.
Dropout and thermal headroom at 800mA
Maximum dropout voltage is 1.3V at 800mA load. For a 1.2V output, the input rail must stay above 2.5V worst-case — a 3.3V rail with 5% tolerance (3.135V min) leaves 0.635V of headroom, which is tight but workable if the input is clean. The 5 mA quiescent current is typical for a low-dropout regulator of this output class; it adds 6 mW to the dissipation budget at 1.2V output.