Dual input charger IC for handheld devices
04 February 2009
Battery charger IC maximises reliability and reduces product footprint with integrated OVP.
AnalogicTech’s AAT3691 is a dual input battery charger IC designed to provide reliable battery charging from multiple sources. 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. Automatic charge selection circuitry recognises which input source offers minimum charging time in terms of input voltage and modifies the charge path, while the integrated over-voltage protection (OVP) protects the battery and system against faulty input up to 28V. The OVP block offers a response of less than 1 microsecond.
The AAT3691 regulates battery charge voltage and current for 4.2V lithium-ion battery cells. It combines a power device with reverse current blocking and current sensing, and is designed to operate from AC adapter inputs and USB ports across a 3.0V to 6.75V (typical) input voltage range. 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 (600 milliohms max).
Safety features include thermal shutdown protection, power on reset and soft start in addition to charging status monitoring and no battery present input (NOBAT) detection functions. An integrated LDO is available on the AAT3695 (to be available Q2, 2009) which can be used to power a transceiver or housekeeping microcontroller on a cell phone or other portable device during the charge cycle to minimise current drawn from the system and shorten charge time.
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