ETA4056

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resumed to full programmed value. When the final float voltage (4.2V) is reached, the ETA4056 enters constant-voltage

mode and the charge current begins to decrease until it drops to 1/10 of the preset value and ends the charge cycle.

Programming Charge Current

The charge current is programmable by setting the value of a precision resistor connected from the ISET pin to ground.

The charge current is 1000 times of the current out of the ISET pin. The charge current out of the BAT pin can be

determined at any time by monitoring the ISET pin voltage using the following equation:

IBAT=

1

Rset

×1000-(

1

3.6

×

1

Rset

×1000)

2

Charge Termination

The ETA4056 keeps monitoring the ISET pin during the charging process. It terminates the charge cycle when the

charge current falls to 1/10 the programmed value after the final float voltage is reached. When the ISET pin voltage

falls below 100mV for longer than tTERM (typically 1ms), charging is terminated. The charge current is latched off and

the ETA4056 enters standby mode, where the input supply current drops to 200μA. (Note: C/10 termination is disabled

in trickle charging and thermal limiting modes).

During charging, the transient response of the circuit can cause the ISET pin to fall below 100mV temporarily before

the battery is fully charged, thus can cause a premature termination of the charge cycle. A 1ms filter time on the

termination comparator can prevent this from happening. Once the average charge current drops below 1/10 the

programmed value, the ETA4056 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 ETA4056 constantly monitors the BAT pin voltage in standby mode and resume another charge cycle if this voltage

drops below the recharge threshold. User can also manually restart a charge cycle in standby mode either by removing

and then reapplied the input voltage or restart the charger using the ISET pin.

Charge Status Indicator (STAT and STDBY pin)

There are 2 different states of the charge status, one is IN CHRGING, and the other is CHARGING FINISHED. STAT

is the pin to pull low during IN CHARGING status and become high impedance in CHARGING FINISHED status. And

STDBY pin just works the opposite way, pulling low after charge finished, and high impedance when in charging.

Table 1:Charger Status Indication

Charger Status

STAT

STDBY

Charging

Low

Hi-Z

End of charge,ISET disable charger only

Hi-Z

Low

Vin OVP,NTC fault

Hi-Z

Hi-Z

No BAT/w BAT Pin has Cap(NTC Pin float/GND)

Blinking,(depend on Cap) Low

No BAT/w BAT Pin has no Cap(NTC Pin float/GND)

Blinking

Hi-Z