AAT3688IWP-4.2-T1 查看數據表（PDF） - Advanced Analogic Technologies

零件编号

产品描述 (功能)

生产厂家

AAT3688IWP-4.2-T1

USB Port Lithium-Ion/Polymer Battery Charger

Advanced Analogic Technologies 

BatteryManagerTM

PRODUCT DATASHEET

AAT3688

USB Port Lithium-Ion/Polymer Battery Charger

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 display definitions.

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 2: LED Display Status Conditions.

The LED anodes should be connected to VUSB. The LEDs

should be biased with as little current as necessary to

create reasonable illumination; therefore, a ballast resis-

tor should be placed between each of the LED cathodes

and the STAT1/2 pins. LED current consumption will add

to the over-thermal power budget for the device pack-

age, hence it is recommended to keep the LED drive

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

most low-cost green, red, or multi-color 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:

Eq. 2: RB(STAT1/2) =

(VUSB - VF(LED))

ILED(STAT1/2)

Example:

RB(STAT1) =

(5.0V - 2.0V)

2mA

=

1.5kΩ

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

2mA.

Table 2 shows the four status LED display conditions.

Digital Charge Status Reporting

The AAT3688 has a comprehensive digital data reporting

system by use of the DATA pin feature. This function can

provide detailed information regarding the state of the

charging system. The DATA pin is a bi-directional port

which will read back a series of data pulses when the

system microcontroller asserts a request pulse. This

single strobe request protocol will invoke one of 14 pos-

sible return pulse counts in which the microcontroller can

look up based on the serial report shown in Table 3.

The DATA pin function is active low and should normally

be pulled high to VUSB. This data line may also be pulled

high to the same level as the high state for the logic I/O

port on the system microcontroller. In order for the

DATA pin control circuit to generate clean sharp edges

for the data output and to maintain the integrity of the

data timing for the system, the pull-up resistor on the

data line should be low enough in value so that the DATA

signal returns to the high state without delay. If the

value of the pull-up resistor used is too high, the strobe

pulse from the system microcontroller may exceed the

maximum pulse time and the DATA output control could

issue false status reports. A 1.5kΩ resistor is recom-

mended when pulling the DATA pin high to 5.0V at the

VUSB input. If the data line is pulled high to a voltage

level less than 5.0V, the pull-up resistor may be calcu-

lated based on a recommended minimum pull-up cur-

rent of 3mA. Use the following formula:

Eq. 3: RPULL-UP ≤

VPULL-UP

3mA

1. Flashing rate depends on output capacitance.

3688.2007.12.1.6

www.analogictech.com

15

Share Link: