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Input Overvoltage Protection

Input Overcurrent Protection

Battery Overvoltage Protection

Thermal Protection

Enable Function

Fault Indication

bq24315

SLUS817 – MARCH 2008

removing power to the output. The response is rapid, with the FET turning off in less than a microsecond. The

monitored all over again. Each time an OCP fault occurs, an internal counter is incremented. If 15 OCP faults

occur in one charge cycle, the FET is turned off permanently. The counter is cleared either by removing and

re-applying input power, or by disabling and re-enabling the device with the CE pin.

To prevent the input voltage from spiking up due to the inductance of the input cable, Q1 is turned off slowly,

resulting in a “soft-stop”.

threshold, the FET Q1 is turned off, and the FAULT pin is driven low. The FET is turned back on once the battery

incremented. If 15 such faults occur in one charge cycle, the FET is turned off permanently. The counter is

cleared either by removing and re-applying input power, or by disabling and re-enabling the device with the CE

pin. For a battery overvoltage fault, Q1 is gradually switched OFF.

The IC has an enable pin which can be used to enable or disable the device. When the CE pin is driven high, the

internal FET is turned off. When the CE pin is low, the FET is turned on if other conditions are safe. The OCP

counter and the Bat-OVP counter are both reset when the device is disabled and re-enabled. The CE pin has an

internal pulldown resistor and can be left floating. Note that the FAULT pin functionality is also disabled when the

CE pin is high.

The FAULT pin is an active-low open-drain output. It is in a high-impedance state when operating conditions are

safe, or when the device is disabled by setting CE high. With CE low, the FAULT pin goes low whenever any of

these events occurs:

• Input overvoltage

• Input overcurrent

• Battery overvoltage

• IC Overtemperature

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