Negative rail regulation — what the -12V fixed output means for the BOM
The MC79L12ACD is a fixed -12V negative-output LDO regulator from Texas Instruments, part of the 79Lxx family. It delivers up to 100 mA from a maximum input of -27V, making it the go-to part for generating a clean -12V rail from a -15V or -24V supply in mixed-signal or op-amp bipolar supply chains.
PSRR and protection — the so-what for the supply designer
PSRR is 42 dB at 120 Hz, which is the full-wave rectifier ripple frequency. That means a 1 Vpp ripple on the input at 120 Hz gets attenuated to about 8 mVpp on the output — good enough for most analog front-ends but not for a high-resolution ADC reference rail without additional post-filtering. Built-in over-temperature and short-circuit protection mean the part thermally limits before the die cracks under a sustained output short — a real-world survival feature when a downstream cap or a mis-wired op-amp pin sinks the rail. Operating temperature range is 0°C to 125°C — commercial-grade silicon. Fine for bench supplies, audio gear, and indoor industrial control; not rated for the -40°C cold start an automotive or outdoor telecom design would need.
Package and board-fit — 8-SOIC footprint
The supplier device package is 8-SOIC — no exposed pad, so thermal dissipation goes through the leads and the copper pour on the board. Supplied in tube packaging — not tape-and-reel, so if your pick-and-place line expects reel feed, you will need a tube feeder or a manual-load step for prototype runs.
Active lifecycle and compliance — sourcing posture
Sourced to order against the BOM line.