The LM3940 is a 1-A low-dropout regulator designed to provide 3.3 V from a 5-V supply. The LM3940 is ideally suited for systems which contain both 5-V and 3.3-V logic, with prime power provided from a 5-V bus. Because the LM3940 is a true low dropout regulator, it can hold its 3.3-V output in regulation with input voltages as low as 4.5 V. The TO-220 package of the LM3940 means that in most applications the full 1 A of load current can be delivered without using an additional heatsink. The surface mount DDPAK/TO-263 package uses minimum board space, and gives excellent power dissipation capability when soldered to a copper plane on the PC board.