I have a need for a voltage regulator such that I can use it to down-convert 5V USB to about 3.3V in order to charge a lithium battery. Ideally:
- Assuming some users may have a faulty micro USB input voltage, it would be nice if it could support input voltages which range from 4V to 6V.
It would be nice if it was not greatly affected by temperature (so for example, if you're charging it outside at -40 degrees, it would be great if the battery could at least hit 3.1V of charge instead of 3.3V). UPDATE: Users have pointed out that below freezing, lithium ion batteries will start to break down because cells will start to plate, so maybe it would be best if the temperature range of the regulator starts between 0 and -20 degrees, or, that the regulator has some thermal protection on it for sub-freezing conditions, or optionally I can leave it up to the user to break his own battery by doing this. If it has an enable signal and my microcontroller comes on at about 2V, then I can warn the user at the very least that what they are doing is destructive.
No leakage current. So, for example if it is connected to the battery and the micro-USB is disconnected, it should not consume any current at all.
- A small package would be very helpful since this is going into a PCB.
- A feature to be able to shut it down from a microcontroller would be nice (an inverted enable signal would be great bonus, so 0 for on and 1 for off, because the microcontroller and battery could be completely dead).
The battery I am using is FDK America's ML2430-HS1.