Chips make charging portables safer

Texas InstrumentsInc. offers battery charger front-end ICsthat increase protection when charging portable electronic devices. The 2mm x 2mm bq243xx safety circuits protect a system from input overvoltage, overcurrent and battery overvoltage conditions that may result from a power spike during charging or from a defective or incorrect wall adapter.

The first member of the family, the bq24314, adds extra protection to a lithium batterywhen a charger circuit fails. The IC can report the fault status to the host processorsuch as TI's DM355 processor (based on its DaVinci technology) or an application processor from TI's Omap3 product family, letting the host processor take corrective action. Under input overvoltage conditions, the bq24314 detects the overvoltage level and disconnects the input to the charger. The device features an input overvoltage threshold of 5.85V. Another version of the circuit, the bq24316, supports a threshold of up to 6.8V. Response time is less than 1µs.

The programmable devicesalso sense and regulate an integrated MOSFET to ensure that the system does not pull an excessive amount of current. The integrated power FET and current sensor support up to 1.5A input current.

Potentially hazardous events may occur if single-cell, Li-ion and Li-polymer batteries are overcharged beyond their float voltage, typically around 4.2 V. Thus, the TI devices offer a second level of protection that helps monitor the battery's voltage.