ETA4056

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7

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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 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 30mV of the battery voltage. If the UVLO comparator is tripped, the charger will not come out of shutdown

mode until VIN rises 100mV above the battery voltage.

Manual Shutdown

There are two methods can disable the IC charger:

1. Driver the EN pin to low.

2. Floating the ISET pin by removing the resistor from ISET pin to ground.

Once one of above conditions happen can put the device in shutdown mode. The battery drain current is thus reduced

to 250nA and the supply current to <50μA. Reconnecting the resistor back or driver EN pin high will restart a new

charge cycle.

Automatic Recharge

After the termination of the charge cycle, the ETA4056 constantly monitors the BAT pin voltage and starts a new charge

cycle when the battery voltage falls below 4.08V, keeping the battery at fully charged condition. ISET pin output enters

a strong pull-down state during recharge cycles.

Battery Temperature Monitoring

ETA4056 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. ETA4056 compares this voltage

against its internal 80%VIN and 45%VIN thresholds to determine if charging is allowed. The temperature sensing circuit

is immune to any fluctuation in VIN, since both the external voltage divider and the internal thresholds 80%VIN and

45%VIN are referenced to VIN. If the NTC pin is connected to GND will disable the temperature-sensing feature.