A single-chip 2B1Q U-interface transceiver

A single-chip transceiver designed to meet the ANSI requirements for the U-interface in the integrated services digital network (ISDN) is described. The device utilizes echo cancellation and the 2B1Q line code to achieve high performance in the presence of near-end crosstalk (NEXT) and other impairments. The 2- mu m, single-metal, double-polysilicon, 5-V CMOS VLSI chip includes all necessary analog and digital signal processing blocks so that a network termination or line termination U-interface can be realized with the addition of a passive line termination circuit and a transformer. Operation over 4.7 km of 0.4-mm or 7.5 km of 0.5 mm cable with a bit error rate of 10/sup -7/ is possible. The performance of the second-order delta-sigma analog/digital converter in response to a 10-kHz sinusoid, assuming a noise bandwidth of 40 kHz (-3 dB), is demonstrated.<
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