YB1880
Standalone Linear Lithium Battery Charger
Programming Charge Current
The charge current is programmed using a single resistor from the PROG pin to ground. The battery charge
current is 1100 times the current out of the PROG pin. The program resistor and the charge current are
calculated using the following equations:
The charge current out of the BAT pin can be determined at any time by monitoring the PROG pin voltage
using the following equation:
Charge Termination
A charge cycle is terminated when the charge current falls to 1/10th the programmed value after the final float
voltage is reached. This condition is detected by using an internal, filtered comparator to monitor the PROG
pin. When the PROG pin voltage falls below 100mV for longer than tTERM (typically 1ms), charging is
terminated. The charge current is latched off and the YB1880 enters standby mode, where the input supply
current drops to 200mA. (Note: C/10 termination is disabled in trickle charging and thermal limiting
modes).When charging, transient loads on the BAT pin can cause the PROG pin to fall below 100mV for short
periods of time before the DC charge current has dropped to 1/10th the programmed value. The 1ms filter
time (tTERM) on the termination comparator ensures that transient loads of this nature do not result in
premature charge cycle termination. Once the average charge current drops below 1/10th the programmed
value, the YB1880 terminates the charge cycle and ceases to provide any current through the BAT pin. In this
state, all loads on the BAT pin must be supplied by the battery. The YB1880 constantly monitors the BAT pin
voltage in standby mode. If this voltage drops below the 4.05V recharge threshold (VRECHRG), another charge
cycle begins and current is once again supplied to the battery. To manually restart a charge cycle when in
standby mode, the input voltage must be removed and reapplied, or the charger must be shut down and
restarted using the PROG pin.
Charge Status Indicator (CHRG)
The charge status output has three different states: strong pull-down (~10mA), weak pull-down (~20μA) and
high impedance. The strong pull-down state indicates that the YB1880 is in a charge cycle. Once the charge
cycle has terminated, the pin state is determined by under voltage lockout conditions. A weak pull-down
indicates that VCC meets the UVLO conditions and the YB1880 is ready to charge. High impedance indicates
that the YB1880 is in under voltage lockout mode: either VCC is less than 100mV above the BAT pin voltage or
insufficient voltage is applied to the VCC pin
YB1880 Rev.1.0
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YOBON [ YOBON TECHNOLOGIES,INC. ]
