5/8
XC6802
Series
■
OPERATIONAL DESCRIPTION (Continued)
<Charge Cycle>
If the BAT pin voltage is less than 2.9V, the charger enters trickle charge mode. In this mode, a safe charge to a battery is
possible because approximately 1/10 of charge current which was set by the I
SEN
pin is supplied to the battery. When the BAT
pin voltage rises more than 2.9V, the charger enters constant-current mode (CC mode) and the battery is charged by the
programmed charge current. When the BAT pin voltage comes to 4.2V, the charger enters constant-voltage mode (CV mode)
automatically. After this, the charge current drops to 1/10 of the programmed charge current and the charge terminates.
<Setting Charge Current>
The charge current can be set by connecting a resistor between the I
SEN
pin and the V
SS
pin. The battery charge current, I
BAT
,
is 1000 times the current out of the I
SEN
pin current, therefore, the charge current, I
BAT
, is calculated by the following equations:
I
BAT
= (V
ISEN
/ R
SEN
) x 1000 (V
ISEN
= 1.0V: Current sense pin voltage)
Use of external components with high accuracy and good temperature characteristics is recommended.
<Charge Termination>
The battery charge is terminated when the charge current decreases to 1/10
of the full charging level after the battery pin
voltage reaches a float voltage. An internal comparator monitors the I
SEN
pin voltage to detect the charge termination. When
the comparator monitors the I
SEN
pin voltage is less than 100mV (charge termination detect) for 1ms (charge termination detect
time), the IC enters stand-by mode. A driver transistor turns off during the stand-by mode. In this state, a failure detection
circuit and a monitoring circuit of the battery pin voltage operates and supply current is reduced to 10
μ
A.
<Automatic Recharge>
The charge cycle resumes when the battery voltage falls and the battery pin voltage becomes less than 4.05V again during the
stand-by mode with 2ms recharge time. For this, the battery does not need any external activation control.