AAT3690 Datasheet, PDF (15/20 Pages) Advanced Analogic Technologies – 1.0A USB Port/Adapter Lithium-Ion/Polymer Battery Charger

AAT3690
1.0A USB Port/Adapter
Lithium-Ion/Polymer Battery Charger
Battery Charge Status Indication
The AAT3690 has two status LED driver outputs.
These two LEDs can indicate simple functions
such as no battery charge activity, battery charg-
ing, 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 AAT3690. 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 accom-
plished 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 2 for LED display definitions.
The LED anodes should be connected to either
V_USB or V_ADP, depending upon the system design
requirements. The LEDs should be biased with as
little current as necessary to create reasonable illu-
mination; therefore, a ballast resistor 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 recom-
mended 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:
R = ^{VI - V} _B(STAT1/2)
ADP
F(LED)
LED(STAT1/2)
Example:
R_B(STAT1) =
5.5V - 2.0V
2mA
= 1.75kΩ
Note: Red LED forward voltage (V_F) is typically
2.0V @ 2mA.
For connection to the USB supply:
R = ^{VI - V} _B(STAT1/2)
USB
F(LED)
LED(STAT1/2)
Example:
R_B(STAT2) =
5.0V - 3.2V
2mA
= 900Ω
Note: Green LED forward voltage (V_F) is typically
3.2V @ 2mA.
The status LED display conditions are described in
Table 2.
Event Description
Charge Disabled or Low Supply
Charge Enabled Without Battery
Battery Charging
Charge Completed
Fault
STAT1
Off
Flash¹
On
Off
On
Table 2: Status LED Display Conditions.
STAT2
Off
Flash¹
Off
On
On
1. Flashing rate depends on output capacitance.
3690.2007.01.1.2
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