AAT3688 查看數據表（PDF） - Advanced Analog Technology, Inc.

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AAT3688

USB Port Lithium-Ion/Polymer Battery Charger

Advanced Analog Technology, Inc. 

AAT3688

USB Port Lithium-Ion/Polymer Battery Charger

Battery Temperature Fault Monitoring

In the event of a battery over-temperature condi-

tion, the charge control will turn off the internal pass

device and report a battery temperature fault on the

DATA pin function. The STAT LEDs will also dis-

play a system fault. After the system recovers

from a temperature fault, the device will resume

charging operation.

The AAT3688 checks battery temperature before

starting the charge cycle, as well as during all

stages of charging. This is accomplished by moni-

toring the voltage at the TS pin. This system is

intended for use negative temperature coefficient

(NTC) thermistors which are typically integrated into

the battery package. Most commonly used NTC

thermistors used in battery packs are approximate-

ly 10kΩ at room temperature (25°C). The TS pin

has been specifically designed to source 80µA of

current to the thermistor. The voltage on the TS pin

that results from the resistive load should stay with-

in a window from 335mV to 2.32V. If the battery

becomes too hot during charging due to an internal

fault, the thermistor will heat up and reduce in value,

thus pulling the TS pin voltage lower than the TS1

threshold, and the AAT3688 will halt charging and

signal the fault condition. If the use of the TS pin

function is not required by the system, it should be

terminated to ground using a 10kΩ resistor.

Battery Charge Status Indication

The AAT3688 indicates the status of the battery

under charge with two different systems. First, the

device has two status LED driver outputs. These

two LEDs can indicate simple functions such as no

battery charge activity, battery charging, charge

complete, and charge fault. The AAT3688 also

provides a bi-directional data reporting function so

that a system microcontroller may interrogate the

DATA pin and read any one of 14 system states.

Status Indicator Display

Simple system charging status may be displayed

using one or two LEDs in conjunction with the

STAT1 and STAT2 pins on the AAT3688. These

two pins are simple switches to connect the display

LED cathodes to ground. It is not necessary to use

both display LEDs if a user simply wants to have a

single lamp to show "charging" or "not charging."

This can be accomplished by just using the STAT1

pin and a single LED. Using two LEDs and both

STAT pins simply gives the user more information

for charging states. Refer to Table 2 for LED dis-

play definitions.

Event Description

Charge Disabled or Low Supply

Charge Enabled Without Battery

Battery Charging

Charge Completed

Fault

STAT1

Off

Flash1

On

Off

On

Table 2: LED Display Status Conditions.

STAT2

Off

Flash1

Off

On

On

1. Flashing rate depends on output capacitance.

3688.2006.10.1.5

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