Integrated circuit having controlled impedance
US6147520A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 18, 1997 |
| Grant date | Nov 14, 2000 |
| Priority date | — |
| Expiry date | Dec 18, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L25/0276
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.