STC4054 Datasheet, PDF (11/17 Pages) STMicroelectronics – 800mA Standalone linear Li-Ion Battery charger with thermal regulation

STC4054
Application information
6.5
Programming charge current
The R_PROG resistor is used to set the charge current value. The battery charge current is
1000 times the Prog pin current value. The program resistor and the charge current are
calculated using the following formula:
R_PROG=1000*V_PROG/I_BAT;
The charge current out of the BAT pin can be monitored through the PROG pin voltage
using the following equation:
I_BAT=(V_PROG/R_PROG)x1000
6.6
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 indicates that the device is
charging the battery. Weak pull-down indicates that V_CC meets the UVLO conditions and the
device is ready to charge. The last status high impedance indicates an insufficient voltage is
applied to the V_CC pin or the voltage on V_CC is less than 100mV above the BAT pin voltage.
6.7
BAT pin
Charge Current Output pin. It provides charge current to the battery and regulates the final
float voltage to 4.2V. An internal precision resistor is used as a feedback loop to compare
the V_O with the reference.
6.8
Charge termination
A charge cycle is terminated when the final float voltage is reached consequently the charge
current falls to 1/10th of the programmed value. The charge is over when the PROG pin
voltage falls below 100mV for longer time than t_TERM (~1ms). The charge current is latched
off, the device enters in standby mode and the input supply current drops to 200µA.
6.9
Automatic recharge
The device restarts the charge cycle when the battery voltage falls below 4.05V to maintain
the battery capacity value higher than 80%. During the recharge time, the CHRG pin goes
low state.
6.10
Soft start
When a charge cycle starts, a internal soft start circuit minimizes the inrush current. At
starting phase, the charge current ramps from zero to the full scale in a 100µs period time.
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