What this -5 V regulator does for your rail
The L7905ACV-DG is a single-output negative linear regulator delivering a fixed -5 V at up to 1.5 A from a -35 V maximum input. Its 60 dB PSRR at 120 Hz makes it a natural choice for post-regulating a negative rail after a rectifier — the ripple rejection at line frequency is where it matters most for analog supplies. The 1.4 V typical dropout at 1 A means the input must sit at least -6.4 V to maintain regulation at that load; plan the input headroom accordingly.
Package, temperature, and protection
Housed in a TO-220-3 through-hole package, it suits point-of-load regulation on a main board or a separate heatsink — the tab is the output pin, so the heatsink carries the -5 V potential. Built-in over-temperature and short-circuit protection let the regulator survive a sustained output short without external foldback circuitry.
STMicroelectronics lists the L7905ACV-DG as Obsolete. The quiescent current is 3 mA, which is modest for a 1.5 A regulator but not low enough for always-on battery applications.