| 摘要 |
<p>PURPOSE:To prevent malfunction by holding the circuit state of a high voltage source system even when the voltage of a low voltage source drops by providing a power-on reset circuit for low voltage source of high voltage source system and a state holding circuit for high voltage source system. CONSTITUTION:When the level of a low voltage source Vcc drops, a H level signal from a power-on reset HPOR circuit for low voltage source of high voltage source system is supplied to the gate of a N channel transistor(NTr) Q5. By this, the NTr Q5 is turned on, the drain of a NTr Q3 is fixed to a L level, a PTr Q2 is turned on and an output T5 of a level shift circuit A1 becomes the H level. Further, a NTr Q6 is turned off and an output terminal 1 becomes a high impedance state. Namely, by holding the state of the level shift circuit A1 even when the low voltage source Vcc is low and inverters 2, 3 become indefinite operating states, the output of a high voltage source system VDD is held to the initial state. Therefore, a malfunction as an IC does not occur.</p> |
