Patent ID: 6501306
Filing Date: 2002-12-31
Classification: G11C,H03K

Abstract:
A data output circuit for a semiconductor device, comprising:an output buffer configured to receive and latch an input data signal with a first voltage range in response to a clock control signal to provide a pair of output data signals; a level shifting circuit comprising both a level shifter and an impedance controller, wherein said level shifting circuit is configured to output impedance drive data to control an impedance state through a pair of output lines in response to a first logic state of an impedance control signal, and wherein said level shifting circuit is further configured to directly receive said output data signal pair from said output buffer in response to a second logic state of said impedance control signal and to transfer a pull-up output data signal and a pull-down output data signal through said output lines, respectively, each of said pull-up and pull-down output data signals having a second voltage range broader than said first voltage range; wherein said level-shifting circuit further comprising a pair of cross-coupled transistors having their gate terminals cross coupled to each other's drain terminals and their source terminals connected in common to an operating voltage; differential transistor means including a pair of transistors having their drain-source channels formed respectively between said drain terminals of said cross-coupled transistors and a ground voltage to define first and second current paths, and having their gate terminals for receiving a pair of output data signals with a first voltage range; high-impedance control means including a pair of transistors, the first said transistor having its drain-source channel formed between a source terminal of said first transistor defining said first current path and said ground voltage and having its gate terminal for receiving a first high-impedance control signal, the second said transistor having its drain-source channel connected in parallel to said drain-source channel of said second transistor defining said second current path, and having its gate terminal for receiving a second high-impedance control signal, said second high-impedance control signal having the opposite logic state to that of said first high-impedance control signal; and pull-up means including a pair of transistors connected in series to any one of said drain terminals of said cross-coupled transistors, said first and second transistors having their drain-source channels connected in series between an output line transferring a pull-down output data signal with a second voltage range and said operating voltage, and having their gate terminals for receiving said first high-impedance control signal and any one of said output data signals; and an output driver for maintaining a data output terminal at said impedance state in response to said impedance drive data from said level shifting circuit and for performing an output driving operation in response to said pull-up and pull-down output data signals from said level shifting circuit to output final data externally through said data output terminal.