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Tiny Li-ion chargers enable safe fast-charging

Posted: 12 Jul 2007 ?? ?Print Version ?Bookmark and Share

Keywords:tiny chargers? Li-ion chargers? safe fast-charging?

Maxim Integrated Products introduces the MAX8804Y/MAX8804Z devices, said to be the industry's smallest, fully integrated, dual-input, standalone, USB/AC-adapter chargers for one-cell Li-ion (Li+) batteries. Capable of shutting off an input voltage higher than 7.5V (typ), as well as withstanding a 30Vdc or 16V USB input, the MAX8804Y/MAX8804Z devices protect against loosely regulated power sources.

Requiring only 6mm? of board space, these chargers also integrate proprietary thermal-regulation and constant-current, constant-voltage (CCCV) circuitry to eliminate overheating during fast-charging and simplify hardware design. The robustness and integration of these tiny chargers make them well suited for use in cellphones, smartphones and other handheld devices in which safety, charging speed and size are of significant concern.

Achieving the performance of two Li+ battery chargers in a tiny, 2-by-3mm footprint, the MAX8804Y/MAX8804Z feature intelligent USB/DC-input circuitry that automatically selects between either a USB or an AC-adapter input source. Additionally, each charger integrates two high-voltage, low-Rds(on) charging FETs, a reverse-current-blocking diode, a current-sensing resistor (RSENSE) and input overvoltage-protection circuitry. To further ensure superior performance, they feature a flexible single-wire interface that enables programming of the charge-current level, they deliver up to 700mA of fast-charging current and they offer a low 2?A battery-leakage current when no input current is attached. The high integration of the MAX8804Y/MAX8804Z significantly simplifies solution implementation, while saving both space and cost.

The main difference between these devices is that they use different charging sequences: before initiating fast charging, MAX8804Z utilizes a prequalification charging stage to bring the battery voltage to 2.5V, whereas the MAX8804Y starts fast-charging without a precharging stage.

The MAX8804Y/MAX8804Z are available in a tiny, thermally enhanced, 8-pin TDFN package that is fully specified over the extended temperature range (-40C to 85C). Prices start at $1.40 each in 2,500-unit pieces).

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