I'm designing a circuit for a very high precision installation, and I need to regulate a 6VDC supply to 5VDC. I have looked at various regulators, but most seem to require at least 2v above the output. It also needs to be very precise, available in a 500mA package, and have a very low current draw. The less external components required, the better. Voltage dividers won't work as the battery will vary in voltage from full to empty.