7805: required input to mantain line regulation

[SounDuke]

Hi, I purchased a 7805CV, looks like this is stopping me from powering MB64 with only a display and a few buttons and pots (ca. 200 mA) with 4 AAs. It is obvious since datasheet says that 7,5 V are required to mantain line regulation. Is there a 7805 which requires at least 6 V? I can't add 2 more AAs due to lacking space on case, I suppose a regulator with low power consumption exist since people who powers their MB with 4 AAs are a lot on this forum, can you give me an hint? Thanks!

[atomsize]

A good way to get around that is to change the 4 AA batteries with a single 9V battery, that way you have enough power to get the machine working. By the way, use a Rechargable battery with more power, so you can always take care of the ambient :)

[jamram]

Hi,

normally voltage regulators are known that they need an input voltage thats about 1.5V for lm317 (up to 3V for 78xx types ) higher than the output voltage.  Maybe the low drop voltage regulator LM2940 is a solution, but there is some extra circuit necessary (there are a lot of examples around in the www) but notice also: 1V difference between input and output is needed,  too. Maybe it's enough to put a dull diode that can handle 200mA directly behind the battery or some z diodes... ... it would cause a drop of 0.6V (and then youre in the working limits for pic...)?

greetinx, jamram

[SounDuke]

I thought about using an lm family regulator, but finally I found space in my case and I added 2 more AAs :D Thanks anyway!