I am designing a circuit for a single-cell Li Polymer battery system. The battery is a 1000 mAh unit and has internal protection. The characteristics of the internal sell protection are:
- over-voltage (over-charge) cutoff point is as low as4.250 V (4.250 to 4.300)
- under-voltage (over-discharge) cutoff point about 2.5 V
I am considering use of the BQ24092 charger:
- voltage-regulation at as high as 4.230 V (4.160 to 4.230 V).
I need a protection IC (like the BQ29797 or the MM3511) but both present problems in our application.
The BQ29797 has over-voltage detection at as low as 4.260 V (4.260 to 4.300) which is 30 mV above the charger's maximum regulation voltage -- so far so good.
But the BQ29797 has under-voltage detection at 2.8 V which, because we want long battery life, is lower than we desire.
The MM3511AB6Y has an under-voltage detection point of 3.0 V which is acceptable.
But the MM3511AB6Y has over-voltage detection at as low as 4.200 V (4.200 to 4.250). The problem here is that the MM3511 could trip on over-voltage before the charger even reached the voltage regulated phase of charging.
Does anyone have a suggestion? I'd like (ideally) a protection IC that has an over-voltage point of 4.260 to 4.300 V and an under-voltage cutoff at 3.0 or even better 3.1 V.
One final note -- not related to the above. We are planning to use the BQ27545-G1 fuel gauge.
