Time-variable decision feedback equalization
View Patent ↗Methods, systems, and devices for techniques for time-variable decision feedback equalization are described. A memory device may be coupled with a host device using one or more conductive lines. A receiver may receive a signal transmitted from another device over a conductive line. The receiver may include a decision circuit used to determine voltages of the received signal based on the received signal and a feedback signal and output an output signal. The receiver may include a variable time-delay circuit configured to output delayed signals that are delayed versions of the output signal and a gain circuit that is configured to scale the delayed signals to generate the feedback signal. The variable time-delay circuit may include delay elements having variable delay parameters. The receiver may be coupled with a memory array that stores the information conveyed by the output signal.
1. A method, comprising:
receiving, at a decision feedback equalization (DFE) circuit of a dynamic random access memory (DRAM) device, an input signal via a Data In or Out (DQ) line of the DRAM device, wherein the DFE circuit comprises a delay circuit including a plurality of delay elements;
configuring, by the delay circuit, the plurality of delay elements to have one of a first configuration of the plurality of delay elements or a second configuration of the plurality of delay elements;
generating, by the delay circuit, after receiving the input signal, one or more delay signals resulting from the input signal in accordance with the one of the first configuration of the plurality of delay elements or the second configuration of the plurality of delay elements that is configured for the plurality of delay elements; and
generating, by a variable gain circuit that comprises a plurality of amplifiers, one or more amplified delay signals in accordance with a first configuration of the plurality of amplifiers, wherein a feedback signal generated by the variable gain circuit comprises the one or more amplified delay signals.
2. The method of claim 1 , wherein configuring the plurality of delay elements comprises:
configuring the plurality of delay elements to have the first configuration of the plurality of delay elements if reflections of the input signal have a first timing distribution; and
configuring the plurality of delay elements to have the second configuration of the plurality of delay elements if the reflections of the input signal have a second timing distribution that is different than the first timing distribution.
3. The method of claim 1 , wherein configuring the plurality of delay elements in accordance with the first configuration of the plurality of delay elements comprises:
aligning delays of the plurality of delay elements with reflections of the input signal, wherein the reflections of the input signal have a timing distribution.
4. The method of claim 1 , wherein configuring the plurality of delay elements in accordance with the first configuration of the plurality of delay elements comprises:
aligning delays of the plurality of delay elements with a subset of reflections of the input signal, wherein the reflections of the input signal have a timing distribution.
5. The method of claim 1 , further comprising:
determining a timing distribution of reflections of the input signal, wherein the plurality of delay elements are configured to have the first configuration of the plurality of delay elements or the second configuration of the plurality of delay elements based at least in part on the timing distribution of the reflections of the input signal.
6. The method of claim 1 , wherein the plurality of delay elements are configurable to have one of a plurality of configurations that corresponds to one of a plurality of timing distributions of reflections of the input signal, the plurality of configurations comprising the first configuration of the plurality of delay elements and the second configuration of the plurality of delay elements.
7. The method of claim 1 , wherein the plurality of delay elements are configurable to:
output a single first delay signal having a first delay based at least in part on the first configuration of the plurality of delay elements being configured; and
output a single second delay signal having a second delay that is different than the first delay signal based at least in part on the second configuration of the plurality of delay elements being configured.
8. The method of claim 1 , wherein the plurality of delay elements are configurable to:
output a single first delay signal having a first delay if a reflection of the input signal having a largest magnitude of a plurality of reflections of the input signal has a third delay that is within a threshold of the first delay; and
output a single second delay signal having a second delay if the reflection of the input signal having the largest magnitude of the plurality of reflections of the input signal has a fourth delay that is within a threshold of the second delay.
9. The method of claim 1 , wherein delay elements of the plurality of delay elements are clocked latches.
10. The method of claim 1 , further comprising:
receiving, at the DFE circuit, a second input signal via the DQ line;
combining the feedback signal with the second input signal; and
outputting, by the DFE circuit, a compensated version of the second input signal to a memory array comprising a plurality of DRAM cells.
11. The method of claim 10 , wherein configuring the plurality of delay elements in accordance with the second configuration of the plurality of delay elements comprises:
adapting delays of the plurality of delay elements to be aligned with reflections of the second input signal, wherein the reflections of the second input signal have a second timing distribution and reflections of the input signal have a first timing distribution that is different than the second timing distribution.
12. The method of claim 10 , wherein configuring the plurality of delay elements in accordance with the second configuration of the plurality of delay elements comprises:
adapting delays of the plurality of delay elements to be aligned with a subset of reflections of the second input signal.
13. The method of claim 1 , wherein the plurality of delay elements are configured in accordance with the first configuration of the plurality of delay elements and the one or more delay signals result from the input signal in accordance with the first configuration of the plurality of delay elements, the method further comprising:
configuring, by the delay circuit after generating the one or more amplified delay signals, the plurality of delay elements in accordance with the second configuration of the plurality of delay elements;
receiving, at the DFE circuit after configuring the plurality of delay elements in accordance with the second configuration, a second input signal via the DQ line;
generating, by the delay circuit, after receiving the second input signal, one or more second delay signals resulting from the second input signal in accordance with the second configuration of the plurality of delay elements; and
generating, by the variable gain circuit, one or more second amplified delay signals in accordance with the first configuration of the plurality of amplifiers, wherein a second feedback signal generated by the variable gain circuit comprises the one or more second amplified delay signals.
14. A dynamic random access memory (DRAM) device, comprising:
a DRAM array comprising capacitive storage elements;
a Data In or Out (DQ) line;
a decision feedback equalization (DFE) circuit coupled with the DRAM array and the DQ line, the DFE circuit configured to receive an input signal via the DQ line, wherein the DFE circuit comprises:
a delay circuit configured to output one or more delay signals resulting from the input signal, the delay circuit comprising a plurality of delay elements configured to generate the one or more delay signals in accordance with one of a plurality of configurations configurable for the plurality of delay elements; and
a gain circuit configured to output one or more amplified delay signals resulting from the one or more delay signals, the gain circuit comprising a plurality of amplifiers configured to generate the one or more amplified delay signals in accordance with one of a plurality of configurations configurable for the plurality of amplifiers, wherein a feedback signal generated by the gain circuit comprises the one or more amplified delay signals,
wherein:
the DFE circuit is further configured to configure, from among the plurality of configurations of the plurality of delay elements, the plurality of delay elements in accordance with a first configuration of the plurality of delay elements or a second configuration of the plurality of delay elements, and
the delay circuit is configured to generate the one or more delay signals in accordance with the one of the first configuration of the plurality of delay elements or the second configuration of the plurality of delay elements that is configured for the plurality of delay elements.
15. The DRAM device of claim 14 , wherein the plurality of delay elements are configurable to:
output a single first delay signal having a first delay based at least in part on the first configuration of the plurality of delay elements being configured; and
output a single second delay signal having a second delay that is different than the first delay signal based at least in part on the second configuration of the plurality of delay elements being configured.
16. The DRAM device of claim 14 , wherein the plurality of delay elements are configurable to:
output a single first delay signal having a first delay if a reflection of the input signal having a largest magnitude of a plurality of reflections of the input signal has a third delay that is within a threshold of the first delay; and
output a single second delay signal having a second delay if the reflection of the input signal having the largest magnitude of the plurality of reflections of the input signal has a fourth delay that is within a threshold of the second delay.
17. The DRAM device of claim 14 , wherein the plurality of delay elements are configurable to output the one or more delay signals to be:
aligned with reflections of the input signal if the reflections of the input signal have a first timing distribution; and
aligned with the reflections of the input signal if the reflections of the input signal have a second timing distribution that is different than the first timing distribution.
18. The DRAM device of claim 14 , wherein the DFE circuit further comprises:
a receiver configured to receive the input signal via the DQ line.
19. The DRAM device of claim 14 , wherein the DFE circuit further comprises:
a circuit configured to combine the feedback signal with one or more input signals that are received over the DQ line after the input signal.
20. The DRAM device of claim 14 , wherein delay elements of the plurality of delay elements are clocked latches.