ETA9185

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7

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Charge Termination

The ETA9185 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 VBAT voltage(4.2V or 4.35V) is reached. When the

ISET pin voltage falls below 100mV for longer than tTERM (typically 180ms), charging is terminated. The charge current

is latched off and the ETA9185 enters standby mode, where the input supply current drops to 2mA. (Note: C/10

termination is disabled in Vhold 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 180ms filter time on the

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

programmed value, the ETA9185 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 ETA9185 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 by removing and

then reapplied the input voltage

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 100°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 500mV. Furthermore, to

protect against reverse current in the power MOSFET, the UVLO circuit keeps the charger in shutdown mode if VIN

falls to within 50mV of the battery voltage for 3mS. If the UVLO comparator is tripped, the charger will not come out of

shutdown mode until VIN rises 100mV above the battery voltage.

Automatic Recharge

After the termination of the charge cycle, the ETA9185 constantly monitors the BAT pin voltage and starts a new charge

cycle when the battery voltage falls below Recharge Voltage, keeping the battery at fully charged condition. ISET pin

output enters a strong pull-down state during recharge cycles.

Battery Temperature Monitoring

ETA9185 continuously monitors temperature by measuring the voltage of NTC pin. A negative or positive temperature

coefficient thermistor and an external voltage divider typically develop this voltage. ETA9185 compares this voltage

against its internal 66%VIN and 35%VIN thresholds to determine if charging is allowed. The temperature sensing circuit