Fixed 15V rail, 1A capacity, DDPAK thermal slug
The LM2940CS-15 is a single-output positive LDO regulator delivering a fixed 15 V output at up to 1 A continuous. The maximum dropout is 0.8 V at full load — at 15 V out, the input rail needs at least 15.8 V to maintain regulation, but the 26 V absolute maximum input gives headroom for unregulated supplies or battery stacks.
Dropout margin and PSRR at line frequency
A 0.8 V maximum dropout at 1 A means the designer must budget at least 800 mV between the input rail and the 15 V output under worst-case load and temperature. The 64 dB PSRR at 120 Hz is measured at the second-harmonic of full-wave rectified line frequency — this part rejects 60/120 Hz ripple well, which is the dominant noise in a post-bridge supply.
Active production, DDPAK thermal management
The DDPAK/TO-263-3 package (also known as D²Pak) has an exposed metal tab on the bottom — the tab is the output pin and the primary thermal path.