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→Options #1: supercap
==Options #1: supercap==
First option uses a couple of 2.5V supercap. The circuit is based on a Linear Technology LTC4425 (Linear SuperCap Charger with Current-Limited Ideal Diode and V/I Monitor) for the charge of the supercaps.
The circuit is configurable with some setting jumpers:
- J2 Enable/Disable the IC
- J3 Select Normal or LDO mode
- J4 Select the maximum charge voltage for the supercap stack
- J5 Select the maximum charge current
J1 is a connector for an external supercap. The resistors R2/R3 select the input Vin failure voltage. Led diode DL1 is a power-fail indicator. When Vin il lower then the supercap stack voltage or when the supercaps aren't charge the led is ON.
''Suggested part number for supercaps: COOPER Bussmann B0810-2R5105-R''
See Linear Technologt LTC4425 datasheet for any other information.
==Options #2: bestcap==
==Options #3: NiMH/NiCd battery==