STC4054

Application information

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6.5

Programming charge current

1000 times the Prog pin current value. The program resistor and the charge current are

calculated using the following formula:

The charge current out of the BAT pin can be monitored through the PROG pin voltage

using the following equation:

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

device is ready to charge. The last status high impedance indicates an insufficient voltage is

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

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

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.