Altera Corporation

Im Whan Kim

Chiakang Sung

Joseph Huang

Bonnie I Wang

Khai Nguyen

Xiaobao Wang

Myron Wai Wong

Wayne Yeung

A programmable input/output circuit for a programmable logic device input/output pin can be configured in a standard I/O mode, or in a reference voltage mode. The circuit includes a tristatable, but otherwise standard I/O buffer as well as a reference voltage clamp circuit. In reference voltage mode, the I/O circuit is tristated, and the reference voltage clamp circuit passes a reference voltage from the I/O pin to a reference voltage bus. In standard I/O mode, the I/O buffer is operational. The reference voltage clamp circuit isolates the I/O pin from the reference voltage bus and may include undervoltage and overvoltage protection to prevent disturbance of the reference voltage bus by an out-of-range I/O signal.

Programmable logic device input/output circuit configurable as reference voltage input circuit

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San Jose, CA, United States of America

Im Whan Kim