AAT3682 データシートの表示（PDF） - Skyworks Solutions

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AAT3682

Li-Ion/Polymer Linear Battery Charger

Skyworks Solutions 

Resuming Charge and the VRCH Threshold

The AAT3682 will automatically resume charging under

most conditions when a battery charge cycle is inter-

rupted. Events such as an input supply interruption or

under voltage, removal and replacement of the battery

under charge, or charging a partially drained battery are

all possible. The AAT3682 will monitor the battery volt-

age and automatically resume charging in the appropri-

ate mode based upon the measured battery cell voltage.

This feature is useful for systems with an unstable input

supply, which could be the case when powering a char-

ger from a USB bus supply. It is also beneficial for charg-

ing or “topping off” partially discharged batteries. The

only restriction on resuming charge of a battery is that

the battery cell voltage must be below the battery

recharge voltage threshold (VRCH) specification. There is

VRCH threshold hysteresis built into the charge control

system. This is done to prevent the charger from errone-

ously turning on and off once a battery charge cycle is

complete.

For example, the AAT3682 has a typical VRCH threshold of

4.1V. A battery under charge is above 4.1V, but is still in

the constant voltage mode because it has not yet

reached 4.2V to complete the charge cycle. If the battery

is removed and then placed back on the charger, the

charge cycle will not resume until the battery voltage

drops below the VRCH threshold. In another case, a bat-

tery under charge is in the constant current mode and

the cell voltage is 3.7V when the input supply is inadver-

tently removed and then restored. The battery is below

the VRCH threshold and the charge cycle will immediately

resume where it left off.

DATA SHEET

AAT3682

Li-Ion/Polymer Linear Battery Charger

LED Display Charge Status Output

The AAT3682 provides a battery charge status output via

the STAT pin. STAT is an open-drain serial data output

capable of displaying five distinct status functions with

one LED connected between the STAT pin and VP. There

are four periods which determine a status word. Under

default conditions, each output period is one second

long; thus one status word will take four seconds to dis-

play through an LED. The five modes include:

1. Sleep/Charge Complete: The IC goes into Sleep

mode when no battery is present -OR- when the

charge cycle is complete.

2. Fault: When an over-current (OC) condition is

detected by the current sense and control circuit

-OR- when an over-voltage (OV) condition is detect-

ed at the BAT pin -OR- when a battery over-temper-

ature fault is detected on the TEMP pin.

3. Battery Conditioning: When the charge system is in

1X or 2X trickle charge mode.

4. Constant Current (CC) Mode: When the system is in

constant current charge mode.

5. Constant Voltage (CV) Mode: When the system is in

constant voltage charge mode.

An additional feature of the LED status display is for a

Battery Not Detected state. When the AAT3682 senses

there is no battery connected to the BAT pin, the STAT

output will turn the LED on and off at a rate dependent

on the size of the output capacitor being used. The LED

cycles on for two periods then remains off for two peri-

ods. See Figure 3 below.

Charge Status

Sleep / Charge Complete

Temp., OC, OV Fault

Battery Conditioning

Constant Current Mode

Constant Voltage Mode

Output Status

off / off / off / off

on / on / off / off

on / on / on / on

on / on / on / off

on / off / off / off

on/off

ON

OFF

ON

OFF

ON

OFF

ON

OFF

ON

OFF

LED Display

on/off on/off

on/off

Figure 3: LED Display Output.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012

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