AAT3685IWP-4.2-1-T1 データシートの表示（PDF） - Analog Technology Inc

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AAT3685IWP-4.2-1-T1

Lithium-Ion/Polymer Battery Charger

Analog Technology Inc 

BatteryManagerTM

within the operating voltage limits as specified in the

Electrical Characteristics section of this datasheet. This

makes the AAT3685 perfect for applications that only

have one input path, but may access either a line adapt-

er source or a USB port supply.

In order to fully utilize the power capacity from a line

adapter or USB port supply, program the SETH charge

rate according to the highest charging current capacity of

the two possible sources, providing that neither supply

exceeds 1A. A lower charge level may be set with the

SETL charge rate and selection of the higher or lower

charge rate is controlled via the PWRSEL function. If the

programmed charge rate is greater than the current

source capacity, there is little danger of system failure

because the AAT3685 charge reduction loop will activate

to automatically reduce the charging current and maintain

a supply voltage set by the CHR threshold. If the input

supply is incapable of maintaining an input voltage great-

er than the under-voltage lockout level of the AAT3685,

the charge control will suspend charging until the source

supply is capable of supplying the minimum input current

to charge. At this point, the AAT3685 will automatically

resume charging in the appropriate mode based on the

battery cell voltage. In case of an over-temperature con-

dition with a high charge current and large input-to-bat-

tery voltage difference, the device will cycle from charging

to thermal shutdown and re-charge after temperature

drops sufficiently, until the battery is charged to 4.2V.

Enable / Disable

The AAT3685 provides an enable function to control the

charger IC on and off. The enable (EN) pin is an active

high. When pulled to a logic low level, the AAT3685 will

be shut down and forced into the sleep state. Charging

will be halted regardless of the battery voltage or charg-

ing state. When the device is re-enabled, the charge

control circuit will automatically reset and resume charg-

ing functions with the appropriate charging mode based

on the battery charge state and measured cell voltage.

Programming Charge Current

The fast charge constant current charge level for the

ADP/USB input is programmed with set resistors placed

between the SETH and SETL pins and ground. The accu-

racy of the fast charge, as well as the preconditioning

trickle charge current, is dominated by the tolerance of

the set resistors used. For this reason, 1% tolerance

metal film resistors are recommended for programming

the desired constant current level.

PRODUCT DATASHEET

AAT3685

Lithium-Ion/Polymer Battery Charger

The fast charge constant current charge control provides

for two current set levels, SETH and SETL. The PWRSEL

pin is used to select the high or low charge current lev-

els. When the PWRSEL pin is pulled to a voltage level

above the VPWRSEL(H) threshold, the SETH current level will

be selected. Conversely, this pin should be pulled below

the VPWRSEL(L) to enable the SETL charge level. These two

charge levels may be set to any level between 50mA and

1A, depending upon the system design requirements for

a given charge application. Refer to Table 1 and Figure 3

for recommended RSETH and RSETL values.

10000

1000

USBL

100

USBH

10

1

10

100

1000

RSET (kΩ)

Figure 3: IFASTCHARGE vs. RSET.

Protection Circuitry

Over-Voltage Protection

An over-voltage event is defined as a condition where

the voltage on the BAT pin exceeds the maximum bat-

tery charge voltage and is set by the over-voltage pro-

tection threshold (VOVP). If an over-voltage condition

occurs, the AAT3685 charge control will shut down the

device until voltage on the BAT pin drops below the over-

voltage protection threshold (VOVP). The AAT3685 will

resume normal charging operation after the over-voltage

condition is removed. During an over-voltage event, the

STAT LEDs will report a system fault; the actual fault

condition may also be read via the DATA pin signal.

Over-Temperature Shutdown

The AAT3685 has a thermal protection control circuit

which will shut down charging functions should the inter-

nal die temperature exceed the preset thermal limit

threshold.

Battery Temperature Fault Monitoring

In the event of a battery over-temperature condition, the

charge control will turn off the internal pass device and

report a battery temperature fault on the DATA pin func-

tion. The STAT LEDs will also display a system fault.

14

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3685.2007.12.1.4

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