AAT3688AIWP-4.2-4-T1 AnalogicTech, AAT3688AIWP-4.2-4-T1 Datasheet - Page 15

• Manufacturer Part Number: AAT3688AIWP-4.2-4-T1
• Description: USB Port Lithium-Ion/Polymer Battery Charger
• Manufacturer: AnalogicTech

1. Flashing rate depends on output capacitance.
BatteryManager
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.
The LED anodes should be connected to V
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:
3688.2007.12.1.6
Charge Enabled Without Battery
Charge Disabled or Low Supply
Table 2: LED Display Status Conditions.
Event Description
Charge Completed
Battery Charging
Eq. 2:
Fault
R
B(STAT1/2)
TM
=
(V
I
USB
LED(STAT1/2)
- V
STAT1
Flash
F(LED)
Off
On
Off
On
USB
1
)
. The LEDs
w w w . a n a l o g i c t e c h . c o m
STAT2
Flash
Off
Off
On
On
1
USB Port Lithium-Ion/Polymer Battery Charger
Example:
Note: Red LED forward voltage (V
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 V
high to the same level as the high state for the logic I/O
port on the system microcontroller.
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.
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
V
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:
USB
input. If the data line is pulled high to a voltage
R
B(STAT1)
Eq. 3:
USB
=
PRODUCT DATASHEET
. This data line may also be pulled
(5.0V - 2.0 V)
R
PULL-UP
2mA
AAT3688
≤
V
F
PULL-UP
3mA
) is typically 2.0V @
= 1.5kΩ
In order for the
If the
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