5V fixed LDO for noise-sensitive analog rails
The LM2931ASX-5.0 is a positive fixed-output low-dropout regulator delivering 5V at up to 100mA. Its 80dB PSRR at 120Hz makes it a natural choice for powering analog front-ends, sensor bias supplies, or microcontroller analog reference rails where ripple rejection matters more than raw output current.
Dropout headroom and protection set
Maximum dropout voltage is 0.3V at the full 100mA load, so the input rail can sit as low as 5.3V and still hold regulation — useful in battery-backed or post-switcher stages where the pre-regulator sags under load. Input voltage tolerance extends to 26V, giving margin for 12V or 24V industrial bus rails without a pre-regulator. On-chip protection includes over-temperature shutdown, reverse polarity blocking, and short-circuit current limiting.
Existing production or repair stock can still be sourced through independent distribution, but new BOMs should qualify an alternative before the last-time-buy window closes.
DDPAK footprint and thermal routing
The DDPAK/TO-263-3 package (3 leads plus exposed tab) is the surface-mount sibling of the TO-220. The tab is the ground path and primary heat sink — the PCB copper area under it sets the junction-to-ambient thermal resistance. For 100mA continuous with a 5V to 5.3V dropout, a 1-inch-square copper pour on the bottom layer keeps the die well below the 85°C operating ceiling.