Quote:
Originally Posted by Mark1960
One thing to watch out for is that the chip enable will be held low when 5v supply is off. Some ram chips will lock out the chip enable when their supply is below a threshold. I’m not sure if the M5M5117 does that. If it doesn’t then the chip is enabled on battery supply and can run the battery down a bit quicker than it should.
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Good point. Maybe I need to look at the enable logic, or put a pullup on /S so that when power is taken off U1 the chip is not enabled, although I'd have to check that won't cause problems if U1 is not powered. As I said, the battery backup was a kind of "nice to have".