AAT3688AIWP-4.2-4-T1 AnalogicTech, AAT3688AIWP-4.2-4-T1 Datasheet - Page 14

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

control circuit will automatically reset and resume charg-
ing functions with the appropriate charging mode based
on the battery charge state and measured cell voltage.
Programming Charge Current
The fast charge constant current charge level for the
USB input is programmed with set resistors placed
between the USBH and USBL pins and ground.
accuracy of the fast charge, as well as the precondition-
ing trickle charge current, is dominated by the tolerance
of the set resistors used. For this reason, 1% tolerance
metal film resistors are recommended for programming
the desired constant current level.
The USB input fast charge constant current charge control
provides for two current set levels, USBH and USBL. The
USBSEL pin is used to select the high or low charge cur-
rent levels in the USB charge mode. When the USBSEL
pin is pulled to a voltage level above the V
old, the USBH current level will be selected. Conversely,
this pin should be pulled below the V
USBL charge level. Typically, the two R
the USBH and USBL functions are fixed for 500mA and
100mA USB fast charge levels.
charge levels may be set to any level between 50mA and
500mA, depending upon the system design requirements
for a given USB charge application. Refer to Table 1 and
Figure 3 for recommended R
Protection Circuitry
Over-Voltage Protection
An over-voltage event is defined as a condition where
the voltage on the BAT pin exceeds the maximum bat-
tery charge voltage and is set by the over-voltage pro-
tection threshold (V
14
BatteryManager
10000
1000
100
10
1
Figure 3: I
USBL
OVP
USBH
TM
10
).
FASTCHARGE
R
If an over-voltage condition
SET
SETH
(kΩ Ω )
and R
vs. R
However, these two
100
USBSEL(L)
SETL
SETH
SET
values.
USBSEL(H)
.
to enable the
and R
w w w . a n a l o g i c t e c h . c o m
thresh-
1000
SETL
The
for
USB Port Lithium-Ion/Polymer Battery Charger
occurs, the AAT3688 charge control will shut down the
device until voltage on the BAT pin drops below the over-
voltage protection threshold (V
resume normal charging operation after the over-voltage
condition is removed. During an over-voltage event, the
STAT LEDs will report a system fault; the actual fault
condition may also be read via the DATA pin signal.
Over-Temperature Shutdown
The AAT3688 has a thermal protection control circuit
which will shut down charging functions should the inter-
nal die temperature exceed the preset thermal limit
threshold.
Battery Temperature Fault Monitoring
In the event of a battery over-temperature condition, the
charge control will turn off the internal pass device and
report a battery temperature fault on the DATA pin func-
tion.
After the system recovers from a temperature fault, the
device will resume charging operation.
The AAT3688 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 tempera-
ture coefficient (NTC) thermistors which are typically
integrated into the battery package.
used NTC thermistors used in battery packs are approx-
imately 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 AAT3688 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.
Battery Charge Status Indication
The AAT3688 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 AAT3688 also provides a bi-directional data report-
ing function so that a system microcontroller may inter-
rogate the DATA pin and read any one of 14 system
states.
The STAT LEDs will also display a system fault.
PRODUCT DATASHEET
AAT3688
OVP
).
The AAT3688 will
3688.2007.12.1.6
Most commonly