National Semi Intros LP3947 Single-Cell USB/AC Charger
National Semiconductor Corp. (Santa Clara, CA) introduced a single-cell USB/ac charger, the LP3947, which is suitable for cellular phones, digital still cameras, MP3 players, personal digital assistants and hand-held instrumentation. The LP3947 charge management system offer extensive battery over-voltage and over-current protection, battery pre-conditioning, and 1% charger voltage accuracy.
The LP3947 is a complete charge management system that safely charges and maintains a lithium-ion battery from either a USB power source or an ac adaptor. Using the USB power source, the LP3947 supports both low-power or high-power charging. Alternatively, the LP3947 can take a charge from the ac adaptor. For the USB power source or ac adaptor, the charge current, battery regulation voltage and end-of-charge point can be selected via an I²C-compatible interface.
The LP3947 also can operate on default values that are pre-programmed in manufacturing. The battery temperature is monitored continuously at the temperature sensor pin to safeguard against hazardous charging conditions. The charger also has under-voltage and over-voltage protection, as well as an internal 5.6 hour timer to protect the battery. The pass transistor and charge current-sensing resistor are all integrated inside the LP3947.
The LP3947 operates in a pre-qualification, constant current, constant voltage and maintenance mode. There are two open drain outputs for status indication. An internal amplifier readily converts the charge current into a voltage. The charger also can operate as a linear regulator, providing a maximum of 1.2 A to the load.
The LP3947 is packaged in a small, thermally enhanced, 16-pin, lead-less lead frame package (LLP®) measuring 4 mm x 4 mm. Available now and priced in 1,000-unit quantities, the LP3947 is $1.05. An evaluation board for the LP3947 is also available.
