Dallas Semiconductor introduces the DS2714, a loose-cell NiMH charger that detects and avoids charging primary alkaline cells, Lithium primary cells, and defective NiMH or NiCd cells. Designed to work with a regulated charge source, the DS2714 can charge from one to four NiMH or NiCd battery cells, including the AA or AAA sizes typically found in many consumer electronics.
From RS Components , the DS2714 charge cycle begins with a precharge qualification test that prevents the fast charging of deeply depleted cells or damaged cells. Deeply depleted cells are charged at a reduced rate to protect them from damage and extend the life of the battery. When each cell reaches a safe threshold, fast charging begins. During the fast-charge phase, the DS2714 tests for inappropriate or damaged cells that should not be charged. Fast charging terminates with the negative-delta-V or flat-V method, and is followed by a top-off phase that completely charges the cells. Finally, a maintenance phase continues indefinitely to keep the cells fully charged.
Besides testing for non-rechargeable or damaged cells, the DS2714 has other features that ensure safe and effective charge operation.
Throughout charging, the DS2714 continuously monitors cell voltages and temperature to assure that they remain within proper ranges.
Whenever the measured values are outside preset thresholds, charging is discontinued and a fault condition is issued. The DS2714 includes an adjustable timer for increased safety and secondary termination.
Additionally, four LED outputs can be used to display charge status and fault conditions.
Typical applications for the DS2714 include desktop/stand-alone loose-cell NiMH or NiCd chargers for digital still cameras, portable music players, and portable electronic games and toys. The device is available in a 20-pin TSSOP package.