Patent ID: 8148944

Claim:
A secondary battery protection semiconductor device for protecting a secondary battery, wherein the secondary battery protection semiconductor device protects the secondary battery by detecting values of at least plural detection items corresponding to the secondary battery including the detection items of overcharge, overdischarge, charge overcurrent, discharge overcurrent, short-circuit current, and overheat; comparing the detected values with corresponding detection levels that are determined beforehand for each of the detection items; and based on the comparison results, turning on/off a discharge control transistor and a charge control transistor that are series-connected to the secondary battery, wherein: among the plural detection items, a first value of a first detection item is detected, and a detection level of a second detection item is changed in accordance with the first value, wherein the secondary battery protection semiconductor device comprises a comparator that compares an input voltage with a reference voltage and outputs an overcharge detection signal, a hysteresis voltage being provided at the input voltage; wherein the secondary battery protection semiconductor device further comprises: an overcharge detection circuit configured to output an overcharge detection signal in response to detecting that a voltage of the secondary battery undergoing a charging operation is at least higher than or equal to a first voltage that is determined beforehand; a control circuit configured to stop the charging operation of the secondary battery in response to the overcharge detection signal; and a temperature detection circuit configured to detect at least one of a temperature of the secondary battery and temperatures of the discharge control transistor and the charge control transistor, wherein: in the event that the temperature detected by the temperature detection circuit is higher than or equal to a predetermined temperature, the overcharge detection circuit outputs the overcharge detection signal in response to detecting that the voltage of the secondary battery undergoing the charging operation is higher than or equal to a second voltage which is lower than the first voltage; and wherein the temperatures detected by the temperature detection circuit are given hysteresis.