AAT3697IWP-4.2-T1 データシートの表示（PDF） - Analog Technology Inc

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AAT3697IWP-4.2-T1

2A Lithium-Ion/Polymer Battery Charger

Analog Technology Inc 

AAT3697

2A Lithium-Ion/Polymer Battery Charger

RT1 and RT2 for use with PTC Thermistor

Eq. 3:

RT1 =

5 ⋅ RTH ⋅ RTC

3 ⋅ (RTH - RTC)

RT2 =

5 ⋅ RTH ⋅ RTC

(2 ⋅ RTH) - (7 ⋅ RTC)

Where RTC is the thermistor's cold temperature

resistance and RTH is the thermistor's hot tempera-

ture resistance. See thermistor specifications for

information. To ensure there is no dependence on

the input supply changes, connect the divider

between VADP and GND. Disabling the tempera-

ture-monitoring function is achieved by applying a

voltage between VTS1 and VTS2 on the TS pin.

Battery Charge Status Indication

The AAT3697 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 AAT3697 also

provides a bi-directional data reporting function so

that a system microcontroller can interrogate the

DATA pin and read any one of 12 system states.

Status Indicator Display

Simple system charging status states can be dis-

played using one or two LEDs in conjunction with

the STAT1 and STAT2 pins on the AAT3697.

These two pins are simple open drain switches

used 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 "charg-

ing" 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 VADP.

The LEDs should be biased with as little current as

necessary to create reasonable illumination; there-

fore, a ballast resistor should be placed between

the LED cathodes and the STAT1/2 pins. LED cur-

rent consumption will add to the overall thermal

power budget for the device package, hence it is

good to keep the LED drive current 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 values can be esti-

mated using the following formulas:

Eq. 4:

R = B(STAT1/2)

(VADP - VF(LED))

ILED(STAT1/2)

Example:

Eq. 5:

RB(STAT1) =

(5.5V - 2.0V)

2mA

=

1.75kΩ

Note: Red LED forward voltage (VF) is typically

2.0V @ 2mA

Event Description

Charge Disabled or Low Supply

Charge Enabled Without Battery

Battery Charging

Charge Completed

Fault

STAT1

Off

Flash1

On

Off

On

Table 3: LED Status Indicator.

STAT2

Off

Flash1

Off

On

On

1. Flashing rate depends on output capacitance.

14

3697.2007.02.1.1

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