| 摘要 |
PURPOSE:To detect accurately the lifetime of a backup cell by providing a power source monitoring circuit which starts an operation of monitoring a voltage value of the backup cell on the basis of making of an external power source and compares the voltage value with a specific voltage, and a data holding circuit which holds and outputs the result of monitoring of the power source monitoring circuit at the time of making of the external power source. CONSTITUTION:When an external power source E1 is made in a memory card 10 wherein a voltage value of a backup cell E2 on the occasion of backup is a specific voltage Vref or below, an output of a comparator 4 becomes a signal of H level showing an alarm state, and this signal is outputted until the voltage value of the backup cell E2 becomes larger than the specific voltage Vref. When a detection signal SG1 generated on the basis of detection of making of the external power source El is outputted by a power-ON detecting circuit 15, in the meantime, an output signal of a latch circuit 16 turns to be of H level. Accordingly, an alarm signal AL of H level of an OR circuit 17 is outputted synchronously with the output of the comparator 4 turning to be of H level and the state of output thereof is held during the time when the external source E1 is made. |
