US Patent No: 6,087,853

Number of patents in Portfolio can not be more than 2000

Controlled output impedance buffer using CMOS technology

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Importance

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Abstract

CMOS technology is used to create a controlled output impedance output buffer circuit. An output buffer driver uses buffer circuits having impedance elements with linear characteristics. A control circuit uses a known impedance load to control the impedance of the buffer circuits. The control circuit monitors a known current flowing through the known impedance load to determine whether the output buffer circuit's output impedance needs to be adjusted to match a transmission line's impedance. Adjustments occur when the control circuit generates control signals to turn on or off various buffer circuits (and their impedance elements) contained within the output driver. In doing so, the output buffer circuit ensures that its output impedance will match the impedance of a transmission line over the entire range of output voltages regardless of the variations caused by the manufacturing process, operation temperature and power supply voltage.

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First Claim

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Patent Owner(s)

Patent OwnerAddressTotal Patents
LUCENT TECHNOLOGIES INC.MURRAY HILL, NJ9561

International Classification(s)

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  • [Patents Count]

Inventor(s)

Inventor Name Address # of filed Patents Total Citations
Huber, Carol A Macungie, PA 4 39
Morris, Bernard L Emmaus, PA 50 425
Patel, Bijit T S. Burlington, VT 6 118

Cited Art

Patent Info (Count) # Cites Year
 
AT&T BELL LABORATORIES (1)
5,334,885 Automatic control of buffer speed 9 1993
 
CYPRESS SEMICONDUCTOR CORPORATION (1)
5,559,447 Output buffer with variable output impedance 43 1994
 
FUJITSU VLSI LIMITED (1)
5,563,539 Output buffer circuit changeable of the output signal from a low to a high impedance state 8 1994
 
HITACHI, LTD. (1)
4,719,369 Output circuit having transistor monitor for matching output impedance to load impedance 171 1986
 
MITSUBISHI DENKI KABUSHIKI KAISHA (1)
5,382,847 Output buffer circuits including voltage compensation 20 1993
 
RAMBUS INC. (1)
5,254,883 Electrical current source circuitry for a bus 336 1992
 
SONY ELECTRONICS INC. (1)
5,457,407 Binary weighted reference circuit for a variable impedance output buffer 157 1994

Patent Citation Ranking

Forward Cites

Patent Info (Count) # Cites Year
 
ROUND ROCK RESEARCH, LLC (11)
7,019,553 Method and circuit for off chip driver control, and memory device using same 13 2003
6,944,071 Active termination circuit and method for controlling the impedance of external integrated circuit terminals 5 2004
7,187,601 Active termination circuit and method for controlling the impedance of external integrated circuit terminals 5 2004
7,106,638 Active termination circuit and method for controlling the impedance of external integrated circuit terminals 7 2004
7,215,579 System and method for mode register control of data bus operating mode and impedance 3 2005
7,715,256 Active termination circuit and method for controlling the impedance of external integrated circuit terminals 1 2006
7,382,667 Active termination circuit and method for controlling the impedance of external integrated circuit terminals 1 2006
7,463,052 Method and circuit for off chip driver control, and memory device using same 2 2006
7,280,410 System and method for mode register control of data bus operating mode and impedance 5 2006
7,936,181 Method and circuit for off chip driver control, and memory device using same 0 2008
8,054,703 Active termination circuit and method for controlling the impedance of external integrated circuit terminals 0 2010
 
INTEL CORPORATION (8)
7,222,208 Simultaneous bidirectional port with synchronization circuit to synchronize the port with another port 3 2000
6,424,175 Biased control loop circuit for setting impedance of output driver 15 2000
6,362,655 Linear active resistor and driver circuit incorporating the same 8 2000
6,448,811 Integrated circuit current reference 16 2001
6,791,356 Bidirectional port with clock channel used for synchronization 15 2001
6,529,037 Voltage mode bidirectional port with data channel used for synchronization 13 2001
6,774,678 Differential cascode current mode driver 1 2003
6,803,790 Bidirectional port with clock channel used for synchronization 18 2003
 
SUN MICROSYSTEMS, INC. (6)
6,323,672 Apparatus for reducing reflections when using dynamic termination logic signaling 1 1999
6,323,673 Apparatus for dynamic termination logic signaling 5 1999
6,232,792 Terminating transmission lines using on-chip terminator circuitry 27 1999
6,188,238 Method for operating an information handling system 0 1999
6,163,165 Method for operating an information handling system 4 1999
6,275,062 Termination of transmission lines using simultaneously enabled pull-up and pull-down circuits 5 1999
 
ANALOG DEVICES, INC. (3)
6,573,794 Operational amplifier 0 2001
6,677,799 Integrator with high gain and fast transient response 2 2001
6,819,168 Integrator with high gain and fast transient response 1 2002
 
HYNIX SEMICONDUCTOR INC. (3)
6,654,310 Semiconductor memory device with an adaptive output driver 12 2002
7,715,249 Semiconductor memory having an output driver equipped with a threshold voltage detecting circuit for adapting the drive capability thereof 2 2008
8,199,591 Data driver 0 2009
 
INTERNATIONAL BUSINESS MACHINES CORPORATION (2)
7,443,194 I/O driver for integrated circuit with output impedance control 0 2008
8,149,014 I/O driver for integrated circuit with output impedance control 0 2008
 
AGERE SYSTEMS INC. (1)
7,218,169 Reference compensation circuit 0 2003
 
HEWLETT-PACKARD COMPANY (1)
6,392,442 Driver circuit that compensates for skin effect losses 0 2000
 
HEWLETT-PACKARD DEVELOPMENT COMPANY, L.P. (1)
7,248,636 Systems and methods for adjusting an output driver 4 2004
 
SAMSUNG ELECTRONICS CO., LTD. (1)
6,429,679 Programmable impedance control circuit and method thereof 20 2001
 
SYNOPSYS, INC. (1)
8,063,623 Analog compensation circuit 1 2007
 
TEXAS INSTRUMENTS INCORPORATED (1)
6,411,126 Output slew rate control for a differential transmission line driver 20 2000