Integrated circuit having controlled impedance

Details Integrated circuit having controlled impedance Integrated circuit having controlled impedance

1997-12-18

2000-11-14

Wells, Kenneth B.

Miscellaneous active electrical nonlinear devices, circuits, and

Specific signal discriminating without subsequent control

By amplitude

327308, 327513, H03K 522

Patent

active

061475203

ABSTRACT:
An integrated circuit includes a controlled impedance that remains relatively constant with respect to variations in processing and temperature. The controlled impedance comprises a fixed resistor in parallel with one or more switchable resistors having a resistance value greater than that of the fixed resistance. Control circuitry includes a reference current generator. The reference current is flowed through a tracking resistor formed of the same material (e.g., doped polysilicon) in the same fabrication process as the fixed resistor. Comparators are used to monitor the voltage across the tracking resistor, and control the switching of the switchable resistors in order to obtain a desired effective resistance. Use of the inventive technique to provide a transmission line termination impedance is described in an illustrative embodiment.

REFERENCES:
patent: 4237405 (1980-12-01), Kellis
patent: 5194765 (1993-03-01), Dunlop et al.
patent: 5243229 (1993-09-01), Gabara et al.
patent: 5298800 (1994-03-01), Dunlop et al.
patent: 5721497 (1998-02-01), Novak
Publication Number 63179563, Date Jul. 23, 1988, Application No. 62012661, Application Date Jan. 21, 1987, Applicant NEC Corp., Inventor--Hara Takaaki, Int. Cl. H01L 27/04--Title: Integrated Circuit--Patent Abstract of Japan only.
"Ds90LV032 3V LVDS Differential Line Receiver", published by National Semiconductor, Dec. 1996, pp. 1-8.
"SN75LVDS86 Flatlink (TM) Receiver", published by Texas Instruments, SLLS268A--Mar. 1997, revised May 1997, pp. 1-14.

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