Back to results
US 7,834,654 B2Granted
Dynamic impedance control for input/output buffers
AssigneeMosaid Technologies Incorporated
InventorBruce Millar
Life of this patent
Estimating the term…
Abstract
A system and method of performing off chip drive (OCD) and on-die termination (ODT) are provided. A common pull-up network composed of transistors and a common pull-down network composed of transistors are employed to implement both of these functions. In drive mode, the pull-up network is configured to produce a calibrated drive impedance when an “on” output is to be generated, and the pull-up network is configured to produce a calibrated drive impedance when an “off” output is to be generated. In termination mode, the pull-up network and the pull-down network are configured to produce a calibrated pull-up resistance and pull-down resistance respectively such that together, they form a split termination.
Claims31
An apparatus comprising:
- a first combined drive and termination circuit configured to operate with a first supply voltage, the first combined drive and termination circuit comprising:
- a variable impedance pull-up network;
- a variable impedance pull-down network ;
- at least one first control input for setting a configuration of the pull-up network;
- at least one second control input for setting a configuration of the pull-down network;
- the apparatus further comprising:
- first pre-drivers connected to the variable impedance pull-up network for configuring the pull-up network by sending a first control signal to the at least one first control input, the first pre-drivers being configured to operate with a second supply voltage higher than the first supply voltage;
- and
- second pre-drivers connected to the variable impedance pull-down network for configuring the pull-down network by sending a second control signal to the at least one second control input, the second pre-drivers being configured to operate with the second supply voltage;
- the apparatus having a termination mode of operation in which the variable impedance pull-up network is configured to have a pull-up network termination impedance and the variable impedance pull-down network is configured to have a pull-down network termination impedance, the pull-up network and the pull-down network in combination functioning as a split termination;
- the apparatus having a drive mode of operation in which:
- to drive a high output, the pull-up network is configured to generate a specific impedance when switched ON;
- to drive a low output, the pull-down network is configured to generate a specific impedance when switched ON.
10 more elements
A method of providing combined drive and termination, the method comprising:
- in a termination mode of operation, configuring a variable impedance pull-up network forming part of a combined drive and termination circuit to have a pull-up network termination impedance and configuring a variable impedance pull-down network forming part of the combined drive and termination circuit to have a pull-down network termination impedance, the pull-up network and the pull-down network in combination functioning as a split termination;
- in a drive mode of operation, to drive a high output, using first pre-drivers to configure the pull-up network to generate a first drive impedance;
- in the drive mode of operation, to drive a low output, using second pre-drivers to configure the pull-down network to generate a second drive impedance;
- supplying a first supply voltage to the combined drive and termination circuit:
- supplying a second supply voltage to the first pre-drivers and the second pre-drivers, the second supply voltage being higher than the first supply voltage.
2 more elements
An apparatus comprising:
- a first combined drive and termination circuit comprising:
- a variable impedance pull-up network;
- a variable impedance pull-down network;
- at least one control input for setting a configuration of the pull-up network;
- at least one control input for setting a configuration of the pull-down network;
- the circuit having a termination mode of operation in which the variable impedance pull-up network is configured to have a pull-up network termination impedance and the variable impedance pull-down network is configured to have a pull-down network termination impedance, the pull-up network and the pull-down network in combination functioning as a split termination;
- the circuit having a drive mode of operation in which:
- to drive a high output, the pull-up network is configured to generate a specific impedance when switched ON;
- to drive a low output, the pull-down network is configured to generate a specific impedance when switched ON;
- the apparatus further comprising:
- pre-driver logic comprising AND-OR-AND logic, that receives a first input to indicate drive high, a second input to indicate drive low, and a third input to indicate termination, and switches between two impedance settings accordingly.
8 more elements
Dependencies are inferred from the claim text.