Method and apparatus for constant output impedance, variable pre-emphasis drive
AssigneeQUALCOMM Incorporated
InventorsMadjid Hafizi, Jie Xu
Life of this patent
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Abstract
A population of drivers is provided in parallel to a driver output and a population of pre-emphasis path drivers is provided in parallel to the driver output. The population of drivers is updated and the population of pre-emphasis path drivers is updated in an inverse relation to the updating of the population of pre-emphasis path drivers. Optionally, the population of drivers has an initial value of n and the population of pre-emphasis path drivers has an initial value of m, and the sum of n and m is P. Optionally, the updated population of n is n′ and the updated population of m is m′, and n′ is approximately equal to P−m′.
Claims12
A method for pre-emphasis drive, comprising:
- driving a driver output according to a given pre-emphasis at a given output impedance, by driving a driver output with a population of n drivers in parallel to the driver output and a concurrent a population of m pre-emphasis path drivers in parallel to the driver output, wherein the sum of n and m is P, wherein the ratio of n to m is based on the given pre-emphasis, and wherein each of the m pre-emphasis drivers has an output impedance of P times the given output impedance and wherein each of the n drivers has an output impedance of P times the given output impedance;
- and
- driving the driver output according to an updated pre-emphasis at said given output impedance, by updating the population of pre-emphasis path drivers from m to m′ and the population of drivers from n to n′, wherein said updating updates m to m′ in an inverse relation to the updating of n to n′ such that the sum of n′ and m′ is maintained at approximately P, and wherein the ratio of n′ to m′ is based on the updated pre-emphasis.
A variable pre-emphasis, constant output impedance line driver, comprising:
- a bank of parallel, selectively enabled drivers having respective outputs coupled to an output node, configured to receive a signal and, if enabled, feed the output node;
- a bank of parallel, selectively enabled pre-emphasis path drivers having respective outputs coupled to the output node, configured to receive a pre-emphasis signal and, if enabled, feed the output node, wherein the selectively enabled pre-emphasis path drivers are configured to have an output impedance approximately equal to P times R_Line if enabled and to have an output impedance significantly greater than P times R_Line if not enabled;
- and
- a pre-emphasis controller configured to receive a pre-emphasis command and, in response, enable m of the selectively enabled pre-emphasis path drivers and n of the selectively enabled drivers, wherein m and n are in accordance with the pre-emphasis command, and wherein m+n=P such that the output impedance at the output node is approximately R_Line,
- wherein the pre-emphasis controller is configured to receive an updated pre-emphasis command and, based on the updated pre-emphasis command, update m to m′ and n to n′ and, in response, enable m′ of the selectively enabled pre-emphasis path drivers and n′ of the selectively enabled drivers, wherein m′ and n′ establish an updated pre-emphasis and m′+n′=P such that the output impedance at the updated pre-emphasis is maintained at approximately R_Line.
A method for pre-emphasis drive comprising:
- step of driving a driver output according to a given pre-emphasis at a given output impedance, wherein said step comprises driving a driver output with a population of n drivers in parallel to the driver output and a concurrent a population of m pre-emphasis path drivers in parallel to the driver output, wherein the sum of n and m is P, wherein the ratio of n to m is based on the given pre-emphasis, and wherein each of the m pre-emphasis drivers has an output impedance of P times the given output impedance and wherein each of the n drivers has an output impedance of P times the given output impedance;
- and
- step of driving the driver output according to an updated pre-emphasis at said given output impedance, by updating the population of pre-emphasis path drivers from m to m′ and the population of drivers from n to n′, wherein said updating updates m to m′ in an inverse relation to the updating of n to n′ such that the sum of n′ and m′ is maintained at approximately P, and wherein the ratio of n′ to m′ is based on the updated pre-emphasis.
An apparatus for pre-emphasis, comprising:
- a population of selectively enabled drivers in parallel to a driver output, wherein each of the selectively enabled drivers is configured to have an output impedance, when enabled, of P times a given output impedance;
- a population of selectively enabled pre-emphasis path drivers in parallel to the driver output, wherein each of the selectively enabled pre-emphasis path drivers is configured to have an output impedance, when enabled, of P times the given output impedance;
- means for driving the driver output according to a given pre-emphasis at a given output impedance, by driving the driver output with n of the selectively drivers concurrently with m of the selectively enabled pre-emphasis path drivers, wherein the sum of n and m is P, wherein the ratio of n to m is based on the given pre-emphasis;
- and
- means for driving the driver output according to an updated pre-emphasis at said given output impedance, by updating the population of pre-emphasis path drivers from m to m′ and the population of drivers from n to n′, wherein said updating updates m to m′ in an inverse relation to the updating of n to n′ such that the sum of n′ and m′ is maintained at approximately P, and wherein the ratio of n′ to m′ is based on the updated pre-emphasis.
A computer-readable non-transitory medium comprising instructions, which, when executed by a processor apparatus coupled to a bank of parallel, selectively enabled drivers coupled to a driver output, each driver having an output impedance of P times a given output impedance when enabled, and to a bank of parallel, selectively enabled pre-emphasis path drivers coupled to the driver output, each pre-emphasis driver having an output impedance of P times the given output impedance when enabled, cause the processor apparatus to perform operations carrying out a method for pre-emphasis, comprising instructions that cause the processor apparatus to:
- drive the driver output according to a given pre-emphasis at the given output impedance, by enabling n of the selectively enabled drivers in parallel to the driver output and concurrently enabling m of the selectively enabled pre-emphasis path drivers in parallel to the driver output, wherein the sum of n and m is P, wherein the ratio of n to m is based on the given pre-emphasis;
- and
- drive the driver output according to an updated pre-emphasis at said given output impedance, by updating the population of pre-emphasis path drivers from m to m′ and updating the population of drivers from n to n′, wherein said updating updates m to m′ in an inverse relation to the updating of n to n′ such that the sum of n′ and m′ is maintained at approximately P, and wherein the ratio of n′ to m′ is based on the updated pre-emphasis.
Dependencies are inferred from the claim text.