UB2016 Datasheet, PDF (6/13 Pages) Unisonic Technologies – ONE-CELL STANDALONE LINEAR LITHIUM BATTERY CHARGER

UB2016
Preliminary
CMOS IC
„ OPERATION
The UTC UB2016 is a single cell lithium-ion battery charger using a constant-current/constant-voltage algorithm. It
can deliver up to 500mA of charge current (using a good thermal PCB layout) with a final float voltage accuracy of
±1.2%. The UTC UB2016 includes an internal P-channel power MOSFET and thermal regulation circuitry. No
blocking diode or external current sense resistor is required; thus, the basic charger circuit requires only two external
components. Furthermore, the UTC UB2016 is capable of operating from a USB power source.
1. Normal Charge Cycle
A charge cycle begins when the voltage at the V_CC pin rises above the UVLO threshold level and a 1% program
resistor is connected from the PROG pin to ground or when a battery is connected to the charger output. If the BAT
pin is less than 2.9V, the charger enters trickle charge mode. In this mode, the UTC UB2016 supplies approximately
1/10 the programmed charge current to bring the battery voltage up to a safe level for full current charging. When the
BAT pin voltage rises above 2.9V, the charger enters constant-current mode, where the programmed charge current
is supplied to the battery. When the BAT pin approaches the final float voltage (4.2V), the UTC UB2016 enters
constant-voltage mode and the charge current begins to decrease. The charge cycle ends when the charge current
drops to 1/10 of the programmed value.
2. 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:
R_PROG
=
1000V
I_CHG
,
I_CHG
=
1000V
R_PROG
The charge current out of the BAT pin can be determined at any time by monitoring the PROG pin voltage using the
following equation:
I_BAT
=
V_PROG
R_PROG
× 1000
This actual current will vary from IC to IC. The typical variation is within ±20%.
3. 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 t_TERM (typically 1ms), charging is terminated. The
charge current is latched off and the UTC UB2016 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 (t_TERM) 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 UTC UB2016
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 UTC UB2016 constantly monitors the BAT pin voltage in standby
mode. If this voltage drops below the 4.1V recharge threshold (V_RECHRG), another charge cycle begins and current is
once again supplied to the battery. To manually restart a charge cycle in standby mode, the input voltage must be
removed and reapplied, or the charger must be shut down and restarted using the PROG pin.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
6 of 13
QW-R502-869.a