bq2903

Note: Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Functional operation should be limited to the Recommended DC Operating Conditions detailed in this data sheet. Exposure to conditions beyond the operational limits for extended periods of time may affect device reliability

The bq2903 is a cost-effective charge controller for rechargeable alkaline batteries such as Renewal batteries from Rayovac. The bq2903 combines sensitive, full-charge detection for three to four rechargeable alkaline cells, with a low-battery cut-off for over-discharge protection.

Designed for integration into a threeor four-cell system, the bq2903 can improve the service life of the rechargeable alkaline cells by properly managing the charge and discharge. The bq2903 requires a voltage-limited current source to generate the proper charge pulses for the Renewal cell. Each cell is individually monitored to ensure full charge without a damaging overcharge.

Charge completion is indicated when the average charge rate falls below approximately 6% of the fast charge rate. Status outputs are provided to indicate charge in progress, charge complete, or fault condition.

The bq2903 avoids over-depleting the battery by using the internal end-of-discharge control circuitry. The bq2903 also eliminates the external power switching transistors needed to separately charge individual Renewal cells.

To reduce external component count, the discharge of bq2903 and charge control FETs are internal to the bq2903; however, if the discharge load is greater than 400mA, a DRV pin is  provided to drive an external N-FET, reducing the effective discharge path resistance for the system.

For safety, charging of bq2903 is inhibited if the voltage of any cell is greater than 3.0V during charge or if the voltage of any cell is less than 0.4V when not charging (open-circuit voltage).