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US 8,134,886 B2Granted
Method and apparatus for reducing oscillation in synchronous circuits
AssigneeMicron Technology, Inc.
InventorYantao Ma
Life of this patent
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Abstract
Control signal oscillation filtering circuits, delay locked loops, clock synchronization methods and devices and systems incorporating the control signal oscillation filtering circuits are described. An oscillation filtering circuit includes a first oscillation filter configured to filter oscillations and a majority filter configured to average filter an output of a phase detector and generate in response thereto control signals to an adjustable delay line.
Claims21
An apparatus, comprising:
- an oscillation filter configured to generate a first valid shift by comparing a present shift with a previously buffered shift received by the oscillation filter;
- and
- a majority filter coupled with the oscillation filter, wherein the majority filter is configured to generate a second valid shift by averaging a quantity of successive shifts received by the majority filter.
An apparatus, comprising:
- a first oscillation filter including oscillation filter input signals for receiving shift left and shift right commands and oscillation filter output signals for outputting oscillation filtered control signals, the first oscillation filter including an output shift left command state, an output shift right command state and at least one no-output state therebetween and further configured to transition toward the output shift left command state when the shift left command is received and to transition toward the output shift right command state when the shift right command is received;
- and
- a majority filter including majority filter input signals for receiving shift left and shift right commands and majority filter output signals for outputting majority filtered control signals, the majority filter configured to output as the majority filter control signals an output shift right command and an output shift left command upon an accumulation of a minimum quantity of each respective command, wherein the first oscillation filter and the majority filter are serially coupled together with an output of one coupled to the input of the other.
A method of filtering shift signals, the method comprising:
- averaging a quantity of successive shift commands to generate a first valid shift command from a majority filter;
- and
- oscillation filtering shift commands to generate a second valid shift command from an oscillation filter.
Dependencies are inferred from the claim text.