POWER-ON CIRCUIT BUILT-IN IC

摘要

PROBLEM TO BE SOLVED: To ensure a high impedance state at a terminal of an IC until an operation start of the IC just after application of a power supply voltage. SOLUTION: This power-on circuit is a circuit built in a synchronous IC memory and provided with a ring counter 10, an output control circuit 52, and a pulse signal interruption circuit 12 or the like. The ring counter 10 continuously generates a pulse signal P when a power supply voltage Vdd is applied to the synchronous IC memory. While the output control circuit 52 received the pulse signal P generated by the ring counter 10, an output terminal DQ of the synchronous IC memory is set to a high impedance. When a pulse signal interruption circuit 12 receives a clock signal CLK, the circuit 12 interrupts the input of the pulse signal P to the output control circuit 52.