Current-mode bidirectional input/output buffer for impedance matching

Abstract

A current-mode bidirectional input/output buffer circuit for impedance matching and operation at a high speed. The current-mode bidirectional input/output buffer circuit communicates with an external chip having the same current-mode bidirectional input/output buffer. In the buffer, a transmitting-receiving average voltage output unit converts an average current value between a transmission signal to be transmitted to the external chip and a receiving signal transmitted from the external chip, into an average voltage. A reference voltage output unit converts a reference current value selectively generated according to a voltage level of the transmission signal, into a reference voltage. A comparator compares the voltage from the transmitting-receiving average voltage output unit to the voltage from the reference voltage output unit to provide a logic signal corresponding to the received signal transmitted from the external chip. A bias voltage generator generates a bias voltage such that the impedance of each output unit is matched with a characteristic impedance of a transmission line coupled to the external chip, and provides the bias voltage to the transmitting-receiving average voltage output unit and the reference voltage output unit. Accordingly, the current-mode bidirectional input/output buffer transmits data between chips at a high rate using a single transmission line and is stable in spite of variations in processes for fabricating chips.

Dependencies are inferred from the claim text.