AAT3689(2007) Ver la hoja de datos (PDF) - Advanced Analogic Technologies

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AAT3689
(Rev.:2007)

0.5A/1.0A USB Port/Adapter Lithium-Ion/Polymer Battery Charger

Advanced Analogic Technologies 

BatteryManagerTM

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AAT3689

0.5A/1.0A USB Port/Adapter Lithium-Ion/Polymer Battery Charger

thermistor will heat up and reduce in value, thus pulling

the TS pin voltage lower than the TS1 threshold and the

AAT3689 will 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 AAT3689 has two status LED driver outputs. These

two LEDs can indicate simple functions such as no bat-

tery charge activity, battery charging, charge complete,

and charge fault.

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 AAT3689. These two pins are simple

switches to connect the 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 using the STAT1

pin and a single LED. Using two LEDs and both STAT pins

simply gives the user more information to the charging

states. Refer to Table 3 for LED display definitions.

The LED anodes should be connected to either VUSB or

VADP, depending upon the system design requirements.

The LEDs should be biased with as little current as nec-

essary to create reasonable illumination; therefore, a

ballast resistor should be placed between the LED cath-

odes and the STAT1/2 pins. LED current consumption

will add to the overall thermal power budget for the

device package, so it is wise to keep the LED drive cur-

rent to a minimum. 2mA should be sufficient to drive

most low-cost green or red LEDs. It is not recommended

to exceed 8mA for driving an individual status LED. The

required ballast resistor value can be estimated using

the following formulas:

For connection to the adapter supply:

Example:

R = VI - V B(STAT1/2)

ADP F(LED)

LED(STAT1/2)

RB(STAT1) =

5.5V - 2.0V

2mA

= 1.75kΩ

Note: Red LED forward voltage (VF) is typically 2.0V @

2mA.

For connection to the USB supply:

R = VI - V B(STAT1/2)

USB

F(LED)

LED(STAT1/2)

Example:

RB(STAT2) =

5.0V - 3.2V

2mA

= 900Ω

Note: Green LED forward voltage (VF) is typically 3.2V @

2mA.

The status LED display conditions are described in Table

3.

Event Description

Charge Disabled or Low Supply

Charge Enabled Without Battery

Battery Charging

Charge Completed

Fault

STAT1

Off

Flash1

On

Off

On

STAT2

Off

Flash1

Off

On

On

Table 3: Status LED Display Conditions.

Capacitor Selection

Input Capacitor

In general, it is good design practice to place a decou-

pling capacitor between the ADP and USB pins and

ground. An input capacitor in the range of 1μF to 22μF

is recommended. If the source supply is unregulated, it

may be necessary to increase the capacitance to keep

the input voltage above the under-voltage lockout

threshold during device enable and when battery charg-

ing is initiated.

If the AAT3689 adapter input is to be used in a system

with an external power supply source, such as a typical

AC-to-DC wall adapter, then a CIN capacitor in the range

of 10μF should be used. A larger input capacitor in this

application will minimize switching or power bounce

effects when the power supply is “hot plugged.” Likewise,

a 10μF or greater input capacitor is recommended for

the USB input to help buffer the effects of USB source

power switching, noise, and input cable impedance.

1. Flashing rate depends on output capacitance.

3689.2007.12.1.1

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