Dallas - Texas Instruments Inc. says its bqTiny-II series of single-cell lithium-ion and Li-P battery charger ICs is the first single-chip solution for charging PDAs, cell phones, digital cameras and wireless headsets from a Universal Serial Bus port or source derived from an ac wall adapter.
Intended for space-limited portable applications, the bqTiny-II device measures 3 x 3 mm in an MLP package. It's highly integrated and includes a power FET and current sensor for up to 1-amp charging from the ac adapter, along with circuitry for high-accuracy current and voltage regulation and automatic selection of either the USB or ac-adapter source. Depending on the version, it also has provision for temperature monitoring and a charge-termination option. In the USB configuration, the host can select from two preset charge rates: 100 or 500 milliamps. In the ac-adapter configuration, users set charge current with an external resistor.
The bqTiny-II devices charge the battery at 4.2 volts in three phases, as is traditionally specified: precharge conditioning, constant current and constant voltage. Charging restarts when battery voltage falls below an internal threshold and the chip will enter a low-power sleep mode via a reverse-blocking protection scheme if both charge sources are removed.
That deep-sleep feature prevents the battery from being drained during such times. In addition, the chip includes charge-status outputs to LEDs or a microcontroller.
Additional features are provided by the specific version of bqTiny-II selected. The features include a temperature-sensing input for detecting hot or cold battery packs; a power-good output that indicates the presence of input power; and a TTL-level timer and taper-detect enable input that enables or disables the fast-charge timer and charge termination.
The bq24020 includes the temperature-sense feature; the bq24022 includes the input-power-present indicator; and the bq24023 includes the input for enabling the fast-charge timer and charge termination. Each is priced at $2.09 in 1,000-piece units.
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