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Power manager allows system operation while charging

Posted: 26 Mar 2007 ?? ?Print Version ?Bookmark and Share

Keywords:power management? battery charger? AnalogicTech? power manager?

AnalogicTech's AAT3670 power-management IC

AnalogicTech claims its AAT3670 power-management IC and intelligent battery charger continuously monitors system power needs during operation and automatically adjusts charge current accordingly, enabling it to deliver the highest possible charge current to the battery. This feature minimizes battery charge time while reducing parts count, BOM and PCB space requirements.

Highly integrated solution
The AAT3670 is a highly integrated 1.6A solution for portable systems powered by single-cell Li-ion/polymer batteries. Integrating a battery charger, current-limited load switches and control circuitry, this intelligent device allows users to simultaneously charge their battery and run their system from an AC adapter or USB port without compromising the battery's charge cycle life and without adding external load switches. The AAT3670 delivers the highest possible charge current to the battery, enabling consumers to experience the fastest possible battery charge time.

The AAT3670 provides dynamic power sourcing to the system load by managing the distribution of power between the source, the battery and the system simultaneously. If the system load exceeds the input supply current capability from the AC adapter or the USB port, the AAT3670 can source additional current from the battery.

A voltage-sensing charge reduction loop monitors the AC adapter input and USB input voltages and automatically prevents voltage sags by throttling back the charge current on the battery depending upon how much current the system load requires. By automatically adjusting charge current only to the extent necessary to maintain input source voltage integrity, this feature helps to simultaneously ensure continuous system operation and minimize battery charge time.

Thermal protection
Under heavy load conditions, depending on PCB layout, the internal IC temperature may increase. Traditional thermal protection is a simple thermal shutdown. Since the AAT3670 supplies power to operate the system, such a shutdown is considered a fault condition and cannot be tolerated. Therefore the AAT3670 contains a digital thermal loop that measures the internal die temperature and reduces charge current if the die temperature exceeds the threshold. Since the battery charger does not get shut down, the digital thermal loop maximizes charge current, given the set of operating conditions.

Battery charge levels on the AAT3670 can be programmed up to 1.6A for AC adapter charger, 0.9A for USB high and 0.1A for USB low charging. Low battery-to-system on resistance minimizes power dissipation and voltage headroom.

The AAT3670 monitors battery temperature and charge states for a variety of fault conditions including overvoltage, shortcircuit and over-temperature. In the event of a fault, the charger will automatically shut down to protect the charging device, the control system and the battery. A battery charger timer also protects the battery and system by terminating charging if the user-programmed charge time is exceeded. Two status monitor output pins are provided to indicate battery charge status via external LEDs.

AnalogicTech's AAT3670 is available in a Pb-free, thermally enhanced 24-pin 4-by-4mm QFN package.

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