Diodes AUR9807 - Manual (Page 18)

Data Sheet
Single-cell Li-Ion Charger IC with System Power Management AUR9807
Nov. 2011 Rev. 1. 0 BCD Semiconductor Manufacturing Limited
18
Charge Function Descriptions (Continued)
The AUR9807 interrupts the charging process when the
battery temperature is out of normal range. It provides a
100µA sensing current to the negative-temperature
coefficient resistor (on the battery side) through the TS
pin. The battery protection is achieved by constantly
monitoring the voltage at the TS pin. When this voltage
is higher than V
LTF
(nominally 2.5V) or lower than
V
HTF
(nominally 0.5V), an under-temperature or
over-temperature condition is detected. For an usual
103AT-type NTC resistor, the corresponding
temperature range is between 0°C and 45°C. The
normal battery temperature range can be modified by
adjusting the NTC resistor or by adding extra resistor
network between the TS pin and the
negative-temperature coefficient resistor. The charging
process would resume after the battery temperature
goes back within the normal range.
Charge Timeout Setting
The charge timeout setting is programmed by the
resistor R
TMR
connected between the TMR and ground
pin. The timeout setting is given by:
t
CHG
= K
TMR
× R
TMR
A suggested 36kΩ R
TMR
gives a 3.6 hrs timeout setting
because the nominal value of K
TMR
is 0.36 sec/Ω. In the
actual charging process, the charging duration is
elongated if the charging current can not reach the
maximum current setting (again this relates to system
loading and environment temperature); therefore, it is
possible that the charging process is still on progress
while the 3.6 hrs timeout limit has been reached. To
circumvent this problem, the actual charging current is
monitored and the clock rate of the timer counter is
halved if the charging current is less than 50% of the
maximum fast charging current. This is equivalent to
modify the timeout setting temporarily by the following
equation:
t
CHG
= K
EXT1
x K
TMR
× R
TMR
, where K
EXT1
=2
If the actual charging current is less than one fourth the
maximum fast charging current, the time out counter
rate is reduced to 25%. The temporary timeout setting
is given by:
t
CHG
= K
EXT2
x K
TMR
× R
TMR
, where K
EXT2
=4
Once the abnormal condition is removed (high
temperature or heavy loading), the charging current
resumes the maximum values (set by R
SET
), and the
time out counter will operate in normal rate.
Charge Status Indicator
Status STAT1 STAT2
Pre-charge ON ON
Constant current and constant
voltage charge
ON OFF
Charge done OFF ON
Fault condition (time out,
sleep mode, or OTP)
OFF OFF
The open drain pins STAT1 and STAT2 provides the
information about the charger status when the CE pin
(chip enable) is set to high. The various charger status
and the corresponding STAT1 and STAT2 levels are
given in the above Table. Connect these pins to the host
processor or LEDS to indicate the charger status.
Short Circuit Protection
AUR9807 provides short circuit protection for both the
input and the battery. When V
IN
is larger than V
BAT
, AC
adapter (or USB port) is chosen as the power source. If
the output voltage is lower than 1V (V
OUT(SC1)
) for more
than t
DGL(SC)
, a short circuit condition is detected; the
power path between the input and the output will be cut
off. The charging process will be interrupted. A 500Ω
resistor is used to pull up the output voltage; if the load
at the output is removed, the output voltage can be
pulled up and the short circuit condition is dissolved.
Similarly, when the battery is chosen as the power
source, an output voltage lower than the battery voltage
by 200mV (V
OUT(SC2)
) longer than t
DGL(SC)
will trigger
the short circuit protection mechanism (this
corresponds to a 5A loading current). A 10mA current
source is used to pull up the output and detect the
removal of the short condition. The power consumption
is less than 5µA under the battery supply mode;
however, AUR9807 is still able to monitor the output
voltage and detect a short circuit condition with this
limiting current budget.
SYSOFF Function
The SYSOFF function is used to cut off the power path
between the battery and the output. This means the