Negative rail regulator in TO-220-3
The LM79M15CT is a fixed -12 V output linear regulator from Texas Instruments, delivering up to 500 mA. The TO-220-3 through-hole package allows direct mounting to a heatsink or chassis for thermal management — the tab is the output pin, so the heatsink path is electrically live and must be isolated or grounded accordingly. With a maximum dropout voltage of 1.1 V at full load, the input rail must stay below -13.1 V (absolute minimum -35 V) to maintain regulation. The 70 dB PSRR at 120 Hz means this regulator rejects rectified ripple from a line-frequency supply, making it a clean source for analog negative rails in op-amp or ADC circuits.
Protection and temperature range
Built-in over-temperature shutdown and short-circuit protection let the regulator survive output faults without external crowbar circuitry. The operating junction temperature range is 0°C to 125°C — suitable for commercial and industrial environments that stay above freezing. Quiescent current is 1.5 mA typical, which is the regulator's own draw when delivering no load — a consideration for always-on rails where standby power matters.