28V Dual Input Linear Li+ Battery Chargers with Battery Detection and Overvoltage-Protected Output

Active: In Production.

The MAX8844Z/MAX8844Y intelligent, stand-alone constant-current, constant-voltage (CCCV), thermally regulated dual input linear chargers are designed for charging a single-cell lithium-ion (Li+) battery. The MAX8844Z/MAX8844Y integrate a current-sense circuit, MOSFET pass element, thermal-regulation circuitry, and eliminate the external reverse-blocking Schottky diode to create the simplest and smallest charging solutions for handheld equipment.

The IC controls the charging sequence from the prequalification state through constant current fast-charge, top-off charge, and full-charge indication. Proprietary thermal-regulation circuitry limits the die temperature during fast-charging or when the IC is exposed to high ambient temperatures, allowing maximum charging current without damaging the IC.

The MAX8844Z/MAX8844Y achieve high flexibility by providing adjustable fast-charge currents (SETI) and an adjustable top-off current threshold (MIN) through external resistors. The IC features a booting assistant circuit that distinguishes input sources and battery connection and provides an enable signal (ABO, active-low ABO) for system booting.

The ICs also integrate two input overvoltage-protected LDO outputs (SAFEOUT, SAFEUSB) for low-voltage-rated USB or charger inputs in system, and a battery pack detection circuit (DETBAT) that disables the charger when the battery pack is absent. Other features include an active-low control input (active-low EN), an active-low input power source detection output (active-low POK), and a fully charged top-off threshold detection output (active-low CHG).

The MAX8844Z/MAX8844Y automatically select between either the USB or IN source. If both sources are present at the same time, highest priority is given to the IN source. The IN source is selected to ensure the shortest charging time for the system since it is able to deliver the highest current.

The MAX8844Z/MAX8844Y accept an input supply range from 4.25V to 28V (IN and USB), but disable charging if the input voltage exceeds +7.5V to protect against unqualified or faulty AC adapters. The ICs operate over the extended temperature range (-40°C to +85°C) and are available in a compact 14-pin, thermally enhanced, lead-free TDFN 3mm x 3mm package (0.8mm max height).

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