US 6,788,124 B1Granted

Method and apparatus for reducing jitter in a delay line and a trim unit

AssigneeXilinx, Inc.

InventorAlireza S. Kaviani

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Abstract

A method and apparatus for reducing jitter in a delay line and trim unit is described. The trim unit includes a plurality of delay elements in parallel. At least one of the plurality of delay elements is controllable between on and off states. At least one of the plurality of delay elements includes at least one filter element to filter local supply noise. At least one of the plurality of delay elements includes a plurality of delay circuits having at least one gated delay circuit to control propagation of a clock signal through the plurality of delay circuits. The plurality of delay elements are configured to maintain an overall propagation delay without adding additional circuitry by sizing at least one delay circuit to provide longer propagation delay and sizing the other delay circuits to provide smaller propagation delay. The plurality of delay circuits are sized and arranged to minimize jitter.

Claims27

Dependent claims

A delay trim unit, comprising:

delay elements coupled in parallel, wherein each of the delay elements receives an input signal and is configured to provide an associated delayed signal version of the input signal, a first portion of the delay elements configured to provide a first set of delay indices corresponding to a first portion of delayed signal versions of the input signal, the first portion of the delay elements providing progressively longer delays of a first granularity, a second portion of the delay elements configured to provide a second set of delay indices corresponding to a second portion of delayed signal versions of the input signal, the second portion of the delay elements providing progressively longer delays of a second granularity different from the first granularity;
a decoder coupled to receive control signals and configured to provide first control signaling and second control signaling responsive to decoding the control signals, the first control signaling for masking all but one delay element of the first portion of the delay elements, the second control signaling for masking all but one delay element of the second portion of the delay elements;
the first portion of the delay elements coupled to receive the first control signaling to mask all but the one delay element of the first portion of the delay elements to obtain a delayed indexed version of the input signal;
the second portion of the delay elements coupled to receive the second control signaling to mask all but the one delay element of the second portion of the delay elements to obtain another delayed indexed version of the input signal;
and
a select circuit coupled to the delay elements to receive the first portion and the second portion of delayed signal versions of the input signal respectively corresponding to the first set of delay indices and the second set of delay indices and configured to provide an output signal responsive to the delayed indexed version of the input signal and the other delay indexed version of the input signal, the output signal having a combined delay of respective delays of the delayed indexed version of the input signal and the other delay indexed version of the input signal.

3 more elements

A delay trim unit, comprising:

delay elements coupled in parallel, wherein each of the delay elements receives an input signal and is configured to provide an associated delayed signal version of the input signal, a first portion of the delay elements configured to provide a first set of delay indices corresponding to a first portion of delayed signal versions of the input signal, the first portion of the delay elements providing progressively longer delays of a first granularity, a second portion of the delay elements configured to provide a second set of delay indices corresponding to a second portion of delayed signal versions of the input signal, the second portion of the delay elements providing progressively longer delays of a second granularity, the second granularity different from the first granularity;
and
a select circuit coupled to the delay elements to receive the first portion and the second portion of delayed signal versions of the input signal respectively corresponding to the first set of delay indices and the second set of delay indices and configured to provide an output signal responsive to a delayed indexed version of the input signal selected from the first portion of the delay elements and another delay indexed version of the input signal selected from the second portion of the delay elements, the output signal having a combined delay of respective delays of the delayed indexed version of the input signal and the other delay indexed version of the input signal, wherein delay spacing between the first set of delay indices is a longer time interval than delay spacing between the second set of delay indices.

Dependencies are inferred from the claim text.

Facts

Application: 10/285,202Filed 31 Oct 2002
Granted: 7 Sep 2004
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

H03K 5/133
Arrangements having a single output and transforming input signals into pulses delivered at desired time intervals: using a chain of active delay…
H03K 2005/00026
Variable delay: controlled by an analog electrical signal, e.g. obtained after conversion by a D/A converter
H03K 2005/00058
Variable delay: controlled by a digital setting
H03K 2005/00156
Layout of the delay element: using opamps, comparators, voltage multipliers or other analog building blocks