ETA4054

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5

Powering Minds of the Smart

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 ETA4054 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 ETA4054 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 ETA4054 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 ETA4054 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 pin)

There are 2 different states of the charge status output, namely strong pull-down (~10mA) and high impedance. The

strong pull-down state indicates that the ETA4054 is in a charge cycle. When the charge cycle has terminated, the pin

state is then determined by under-voltage lockout conditions. If VIN meets the UVLO conditions, device is in high-

impedance status and is ready to charge. If the difference between VIN and BAT pin voltage is less than 100mV or

insufficient voltage is applied to the VIN pin, High impedance appears on the charge statues pin.

High Temperature Fold-back

Build-in feedback circuitry mechanism can reduce the value of the programmed charge current once the die

temperature tends to rise above 50°C, hence prevents the temperature from further increase and ensure device safe

operation.

Under-voltage Lockout (UVLO)

Build-in under-voltage lockout circuit monitors the input voltage and keeps the charger in shutdown mode until VIN

rises above the under-voltage lockout threshold. The UVLO circuit has a built-in hysteresis of 200mV. Furthermore, to