AAT3670 データシートの表示（PDF） - Advanced Analogic Technologies

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AAT3670

1.6A Dynamic Battery Charger and Power Manager

Advanced Analogic Technologies 

BatteryManagerTM

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AAT3670

1.6A Dynamic Battery Charger and Power Manager

ADP charging and up to 0.9A for USB charging. During

battery charge, the AAT3670 pre-conditions (trickle

charge) the battery with lower current when the battery

voltage is less than 2.9V, and it charges the battery in a

constant current mode when the battery voltage is above

2.9V. When the battery voltage rises to 4.2V, the charger

will automatically switch to a constant voltage mode until

the charge current is reduced to the programmed charge

termination current threshold. The internal arrangement

of load switches and charge regulation device also pro-

vide dynamic power sourcing to the system load. If the

system load exceeds the input current supply from the

adapter or USB source, additional current can be sourced

from the battery cell. At all times, the device will manage

distribution of power between the source, the battery and

the system simultaneously in order to support system

power needs and charge the battery cell with the maxi-

mum amount of current possible.

The AAT3670 has a unique internal charge current

reduction loop control that will prevent an input source

from overload. In the case of USB charging from a USB

port VBUS supply, there are two events which need to be

guarded against. The first is charging from a defective or

inadequate USB host supply; the second problem could

arise if the programmed USB charge current plus the

system supply demand through the AAT3670 exceeds

the ability of a given USB port. In either case, the

AAT3670 charge reduction (CHR) loop will activate when

the input source to the USB input drops below the VCHR_TH

threshold of 4.5V. The CHR loop will automatically reduce

the charge current to the battery until the supply voltage

recovers to a point above the VCHR_TH threshold. The CHR

loop protection system also operates in the adapter input

mode with a 4.6V VCHR_TH threshold. This protects the

charger, system and source supply in the event an

adapter or power source does not meet the ADP charg-

ing mode specification. In USB or adapter mode charg-

ing, the CHR system will permit the charging of a battery

cell with the maximum possible amount of charge cur-

rent for any given source fault condition.

During battery charging, the device temperature will

rise. In some cases with adapter (ADP) charging, the

power dissipation in the device may cause the junction

temperature to rise to close to its thermal shutdown

threshold. In the event of an internal over-temperature

condition caused by excessive ambient operating tem-

perature or excessive power dissipation condition, the

AAT3670 enables a digitally controlled thermal loop sys-

tem that will reduce the charging current to prevent the

device from thermal shutdown. The digital thermal loop

will maintain the maximum possible battery charging

current for the given set of input to output power dissi-

pation and ambient temperature conditions. The digital

thermal loop control is dynamic in the sense that it will

continue to adjust the battery charging current as oper-

ating conditions change. The digital thermal loop will

reset and resume normal operation when the power dis-

sipation or over-temperature conditions are removed.

Battery temperature and charge state are fully moni-

tored for fault conditions. In the event of an over-volt-

age, over-current, or over-temperature failure, the

device will automatically shut down, thus protecting the

charging device, control system, and the battery under

charge. In addition to internal charge controller thermal

protection, the AAT3670 also provides a temperature

sense feedback function (VTS/TS pins) from the battery

to shut down the device in the event the battery exceeds

its own thermal limit during charging. All fault events are

reported to the user by two simple status LEDs.

Charging Operation

The AAT3670 has four basic modes for the battery

charge cycle regardless of which charge input function is

selected, either the adapter input or USB input: pre-

conditioning/trickle charge, constant current fast charge,

constant voltage, and end of charge/sleep mode.

Battery Preconditioning

Before the start of charging, the AAT3670 checks sev-

eral conditions in order to assure a safe charging envi-

ronment. The input supply must be above the minimum

operating voltage, or under-voltage lockout threshold

(VUVLO), for the charging sequence to begin. Also, the cell

temperature, as reported by a thermistor connected to

the TS pin from the battery, must be within the proper

window for safe charging. When these conditions have

been met and a battery is connected to the BAT pin, the

AAT3670 checks the state of the battery via the battery

voltage sensing (BATS) pin. If the cell voltage is below

the preconditioning voltage threshold (VMIN), the AAT3670

begins preconditioning the cell.

3670.2008.04.1.5

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