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Charger IC offers up to 28V overvoltage protection

Posted: 20 Jan 2009 ?? ?Print Version ?Bookmark and Share

Keywords:charger IC? overvoltage protection feature? Li-ion battery?


Advanced Analogic Technologies Inc. has developed the AAT3691, a dual input battery charger IC with integrated overvoltage protection (OVP) up to 28V.

Designed to meet industry requirements for highly flexible and reliable battery charging from multiple sources, the new battery charger supports inputs from both AC adapters and USB ports in applications such as mobile phones, digital still cameras and other handheld devices. The charger assesses which input source offers minimum charging time and modifies the charge path, while the integrated OVP protects the battery and system against faulty input.

"Today's portable system designers need a battery charging solution that not only supports input from both AC adapters and USB ports, but also protects the battery, the charger and the system," says Siamak Bastani, AnalogicTech product line director. "By integrating OVP protection up to 28V for both inputs, the AAT3691 helps designers maximize charging flexibility and reliability while reducing parts count and end product footprint."

Integrated OVP
The AAT3691 is designed to regulate battery charge voltage and current for 4.2V Li-ion battery cells used in a wide variety of portable systems. As an integrated battery charger IC which combines a power device, reverse current blocking and current sensing, the device is designed to operate from AC adapter inputs and USB ports across a 3.0V to 6.75V (typical) input voltage range.

To maximize safety, the AAT3691 adds integrated OVP up to 28V. The OVP block offers an extremely fast response of Charge current can be programmed up to 1.6A for charging via an ADP and up to 0.5A for charging via a USB port using external resistors. When ADP or USB input power exceeds 6.75V typical, an internal series switch opens preventing damage to the battery or charging circuit. Charging and OVP total ON resistance (RDS(ON)) for the AAT3691 is a very low 600m? (max). Automatic charge selection circuitry recognizes the best charging source in terms of input voltage and other criteria and modifies the charge path to minimize charge time.

The AAT3691 also features a no battery present input detection function which prevents input power from passing through the OVP block and suspends charging when no battery is present or a battery trace or connector is defective.

Additionally, the new charger IC offers a variety of other protection features to protect the charging device, the control system and the battery. Battery charging status is continually monitored for fault conditions. Safety features include thermal shutdown protection, power on reset and soft start.

Modified version
AnalogicTech is also offering a slightly modified version of the AAT3691 which provides all the features described above and adds an integrated LDO. The LDO on the AAT3695 (to be available Q2 09) can be used to power a transceiver or housekeeping microcontroller on a cellphone or other portable device during the charge cycle, minimize current draw from the system and shorten charge time.

The AAT3691 is qualified across the -40C to +85C temperature range. It is available in a 16-pin 3mm x 4mm TDFN package for $1.12 in 1,000 quantities.

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