AAT3691 charger IC provides charging flexibility

By integrating over-voltage protection (OVP) up to 28V for both inputs, AnalogicTech's AAT3691 helps designers maximise charging flexibility and reliability while reducing parts count and end-product footprint.

The 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.

The AAT3691 is designed to regulate battery charge voltage and current for 4.2V lithium-ion battery cells used in a variety of portable systems.

As an integrated battery charger IC that 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 maximise safety, the AAT3691 adds integrated OVP up to 28V.

The OVP block offers a fast response of less than one microsecond.

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 for the AAT3691 is 600 milliohms maximum.

Automatic charge selection circuitry recognises the best charging source in terms of input voltage and other criteria and modifies the charge path to minimise charge time.

The AAT3691 also features a no-battery-present input detection function that 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.

The charger IC also offers a variety of other 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.

AnalogicTech is also offering a slightly modified version of the AAT3691 that provides all the features described above and adds an integrated LDO.

The LDO on the AAT3695 (to be available in quarter two 2009) can be used to power a transceiver or housekeeping microcontroller on a cell phone or other portable device during the charge cycle, minimise 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 3 x 4 mm TDFN package.