Fixed 4.7 V rail for noise-sensitive loads
The LP2980AIM5-4.7 is a single-output positive LDO regulator from Texas Instruments, delivering a fixed 4.7 V output at up to 50 mA.
Maximum dropout voltage is 0.22 V at the full 50 mA load. That means the input must stay above 4.92 V to maintain regulation — a tight margin if the input is a 5 V rail with tolerance. The PSRR of 63 dB at 1 kHz gives about 0.7 mV ripple rejection per millivolt of input ripple, which is adequate for powering analog front-ends or sensor bias circuits where 1 kHz switching noise from a buck converter needs attenuation. For battery-powered designs drawing a few milliamps total, the 95 µA overhead is noticeable but acceptable for a fixed-output LDO with enable capability.
For BOM lines that require this exact fixed 4.7 V output in SOT-23-5, procurement must rely on surplus or broker channels.
The regulator includes an enable pin for on/off control, plus built-in protection against over-current, over-temperature, and short-circuit conditions. These features reduce external component count in designs where a simple enable signal from a microcontroller or supervisor IC gates the rail.