AAT2550_08 Datasheet, PDF (19/34 Pages) Advanced Analogic Technologies – Total Power Solution for Portable Applications

SystemPower^TM
PRODUCT DATASHEET
AAT2550178
Total Power Solution for Portable Applications
If the use of the TS pin function is not required by the
system, it should be terminated to ground with a 10kΩ
resistor.
Battery Charge Status Indication
The AAT2550 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 indi-
cate simple functions such as no battery charge activity,
battery charging, charge complete, and charge fault. The
AAT2550 also provides a bi-directional data reporting
function so that a system microcontroller can interrogate
the DATA pin and read any one of 13 system states.
Status Indicator Display
Simple system charging status states can be displayed
using one or two LEDs in conjunction with the STAT1 and
STAT2 pins on the AAT2550. 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 ADP. The LEDs
should be biased with as little current as necessary to
create reasonable illumination; therefore, a ballast resis-
tor should be placed between the LED cathodes 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 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 driv-
ing 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)
R_B(STAT1) =
5.5V - 2.0V
2mA
= 1.75kΩ
Note: Red LED forward voltage (V_F) is typically 2.0V @
2mA. Green LED forward voltage (V_F) is typically 3.2V @
2mA.
The four 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.
Digital Charge Status Reporting
The AAT2550 has a comprehensive digital data reporting
system by use of the DATA pin feature. This function can
provide detailed information regarding the status 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 sin-
gle strobe request protocol will invoke one of 13 possible
return pulse counts which the microcontroller can look up
based on the serial report table shown in Table 4.
Number
1
2
3
4
5
6
7
8
9
10
11
12
23
DATA Report Status
Chip Over-Temperature Shutdown
Battery Temperature Fault
Over-Voltage Turn Off
Not Used
ADP Watchdog Time-Out in
Battery Condition Mode
ADP Battery Condition Mode
ADP Watchdog Time-Out in
Constant Current Mode
ADP Thermal Loop Regulation in
Constant Current Mode
ADP Constant Current Mode
ADP Watchdog Time-Out in
Constant Voltage Mode
ADP Constant Voltage Mode
ADP End of Charging
Data Report Error
Table 4: Serial Data Report Table.
1. Flashing rate depends on output capacitance.
2550.2008.02.1.3
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