Charge Management ICs Play It Cool In PortableProducts

A family of charge-management chips, the bq2420x, claim to reduce heat dissipation in portable systems by up to 70% compared to linear chargers. Integrating the charge control MOSFET and current sensor in a eight-pin MSOP, the devices require only two small external capacitors for operation. They are capable of completing the charge cycle in three phases: conditioning, current limit, and constant voltage. During the conditioning phase, a pre-charge is applied to rejuvinate a nearly depleted battery. After that, the devices rely on an external, current-limited power source to charge the battery. This scheme is said to remove more than 70% of the heat as opposed to a similar linear charger. And a voltage-regulation phase completes the battery charge and the internal reference is trimmed to within ±0.5% across the operating temperature and voltage range. Charge terminates when minimum current is reached or if the battery fails to reach a minimum voltage. Price: $1.48 each/1,000. TEXAS INSTRUMENTS, INC., Dallas, TX. (972) 644-5580.