Patent ID: 6160457
Filing Date: 2000-12-12
Classification: H03B

Abstract:
A universal crystal-oscillator input/output (I/O) circuit for use with an ASIC device with charge device mode (CDM) electrostatic discharge (ESD) protection, which comprises:a first P-type metal-oxide semiconductor (PMOS) transistor, whose source is connected to a system voltage;a second PMOS transistor whose source is connected to the system voltage and whose gate is connected to the drain of the first PMOS transistor;a third PMOS transistor, whose source is connected to the system voltage and whose drain is connected to the drain of the second PMOS transistor;a first N-type metal-oxide semiconductor (NMOS) transistor, whose source is grounded and whose drain is connected to the drain of the first PMOS transistor;a second NMOS transistor, whose source is grounded, whose gate is connected to the drain of the first NMOS transistor, and whose drain is connected to the drain of the second PMOS transistor;a third NMOS transistor, whose source is tied to the gate thereof and grounded, and whose drain is connected both to the drain of the third PMOS transistor and to the drain of the second NMOS transistor; anda control logic unit having three output ports respectively connected to the gate of the first PMOS transistor, the gate of the third PMOS transistor, and the gate of the first NMOS transistor, for selectively controlling the respective ON/OFF states of the first PMOS transistor, the third PMOS transistor, and the first NMOS transistor.