AAT3685IWP-4.2-T1 Analogic Tech, AAT3685IWP-4.2-T1 Datasheet - Page 15
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AAT3685IWP-4.2-T1
Manufacturer Part Number
AAT3685IWP-4.2-T1
Description
Battery Management Lithium-Ion/Polymer Battery Charger
Manufacturer
Analogic Tech
Datasheet
1.AAT3685IWP-4.2-T1.pdf
(21 pages)
Specifications of AAT3685IWP-4.2-T1
Package / Case
TDFN33-12
Mounting Style
SMD/SMT
Lead Free Status / Rohs Status
Lead free / RoHS Compliant
Available stocks
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Part Number:
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Part Number:
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BatteryManager
After the system recovers from a temperature fault, the
device will resume charging operation.
The AAT3685 checks battery temperature before starting
the charge cycle, as well as during all stages of charging.
This is accomplished by monitoring the voltage at the TS
pin. This system is intended for use negative temperature
coefficient (NTC) thermistors which are typically inte-
grated into the battery package. Most commonly used
NTC thermistors used in battery packs are approximately
10kΩ at room temperature (25°C). The TS pin has been
specifically designed to source 80μA of current to the
thermistor. The voltage on the TS pin that results from
the resistive load should stay within a window from
335mV to 2.32V. If the battery becomes too hot during
charging due to an internal fault, the thermistor will heat
up and reduce in value, thus pulling the TS pin voltage
lower than the TS1 threshold, and the AAT3685 will halt
charging and signal the fault condition. If the use of the
TS pin function is not required by the system, it should be
terminated to ground using a 10kΩ resistor. Alternatively,
on the AAT3685-1, the TS pin may be left open.
Battery Charge Status Indication
The AAT3685 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
AAT3685 also provides a bi-directional data reporting
function so that a system microcontroller may interrogate
the DATA pin and read any one of 14 system states.
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 AAT3685. 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.
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The LED anodes should be connected to V
LEDs should be biased with as little current as necessary
to create reasonable illumination; therefore, a ballast
resistor should be placed between each of the LED cath-
odes and the STAT1/2 pins. LED current consumption
will add to the over-thermal power budget for the device
package, 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:
Example:
Note: Red LED forward voltage (V
2mA.
Table 2 shows the four status LED display conditions.
Digital Charge Status Reporting
The AAT3685 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.
Charge Enabled Without Battery
Charge Disabled or Low Supply
Lithium-Ion/Polymer Battery Charger
Table 2: LED Display Status Conditions.
Event Description
Charge Completed
Battery Charging
Eq. 2:
R
B(STAT1)
Fault
R
B(STAT1/2)
=
PRODUCT DATASHEET
(5.0V - 2.0 V)
=
2mA
(V
AAT3685
APD/USB
I
LED(STAT1/2)
F
STAT1
) is typically 2.0V @
Flash1
= 1.5kΩ
Off
On
Off
On
- V
F(LED)
ADP/USB
)
STAT2
Flash1
Off
Off
On
On
.
The
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