Low-Voltage Protection, Constant Brightness
This board uses a Voltage Reset Monitor to provide LVP and an LDO to provide a constant voltage (an in effect, constant current). Everything is on a single side for quick & easy reflow soldering. It’s dual-channel, but includes a Bridge pad for making it single-channel.
- LVP: MAX809SQ293D1T1G, a 2.93V active-low Voltage Reset Monitor with 0.5uA quiescent current
- LDO: NCP553SQ30T1G, a 3V “NoCap” LDO with a 2.8uA quiescent current (typical)
- FET: PFET, size SC-70 / SOT-323 (such as BSS209PWH6327XTSA1) or NTS2101PT1G
- LEDs: 0805 size
- Resistors: 0603 size
So altogether, there should be a total quiescent current of around 3.3uA while the tailcap is lit, going down to 0.5uA after LVP trips. In comparison to the current for the LEDs (typically 0.15mA = 150uA or higher, this is absolutely minimal)
Standard (16mm): Oshpark
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Big Switch (19mm): Oshpark (warning - the 19mm doesn’t have reverse polarity protection!)
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Testing video:
