| 摘要 |
<p>PURPOSE:To reduce the loss of a regulator by providing the portable information machine with a voltage detecting circuit for switching a main battery and a backup secondary battery, a voltage switching means for dropping a power supply voltage when a CPU generates a fault and a backup means for supplying backup power only to a memory. CONSTITUTION:In a dormant state, a HALT signal is in a LO level, an analog switch 106 is turned off and an analog switch 107 is turned on. Thereby, a resistor 104 is validated, the voltage of a point (a) is turned to the ground level and the output of the regulator 102 is set up to the charging voltage of the secondary battery 114 to start charging. In a backup state, the state is detected by a voltage monitoring IC 103, a transistor(TR) 110 is turned off, a signal line (b) is turned to a HI level, the output of an OR gate 118 is fixed on HI, and the memory 117 does not receive a CE from the CPU and is turned to a stand-by state. Then, the secondary battery 114 starts to discharge to supply the backup voltage of the memory 117. Thus, the loss of the regulator can be reduced.</p> |
