NATIONAL Semiconductor, represented by Arrow Electronics , has released two battery charging products for portable electronics, a single-cell USB/ac charger and a charge control and protection circuit for embedded Lithium-Ion and Lithium-polymer batteries.
They are suitable for mobile phones, digital still cameras, MP3 players, personal digital assistants (PDAs) and handheld instrumentation. They require few external components and support up to 1.2A of a full-rated current.
The LP3947 charge management system and LM3655 battery protection IC offer extensive battery over-voltage and over-current protection, battery pre-conditioning and 1% charger voltage accuracy. They are packaged in a small thermally-enhanced leadless leadframe (LP3947) and a very small micro SMD (LM3655) package.
The LP3947 is a complete charge management system that safely charges and maintains a Li-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 (EOC) 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 four modes: pre-qualification, constant current, constant voltage and maintenance. 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 1.2A to the load.
The LP3947 is available in a tiny, thermally enhanced 16-pin LLP package measuring 4mm by 4mm.