Due to some fairly tight physical constraints, I need to use a fairly small battery for my RTC. 20mm, 12mm and even 10mm are all too large and I'm looking at using a 6.8mm ML621 which is a rechargeable 5mah. Rough calculations suggest this should last around 100 days for the RTC, which is fine as this will rarely go 100 days without use, but means I need to ensure that I can charge it when the unit powers on.
Panasonics recommended charging circuit is fairly straight forward, just a Schottky to drop the voltage (Max charge voltage on the battery is 3.2v) and a resistor of specified value, so I was hoping to use something like this
I know there is a diode already on the 3v3 -> VBat line though and just wanted to make this wasn't going to interfere with anything that's already happening on that circuit. Does this setup seem reasonable?
Panasonics recommended charging circuit is fairly straight forward, just a Schottky to drop the voltage (Max charge voltage on the battery is 3.2v) and a resistor of specified value, so I was hoping to use something like this
I know there is a diode already on the 3v3 -> VBat line though and just wanted to make this wasn't going to interfere with anything that's already happening on that circuit. Does this setup seem reasonable?