DRAM

Some DRAM cells have a data retention time that irregularly switches between longer and shorter values over time. What is this phenomenon called?

  1. AVRT (variable retention time)
  2. BSoft error
  3. CRow hammer
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Answer: A. VRT (variable retention time)

VRT (variable retention time) is a phenomenon in which a cell's leakage current switches due to changes in the state of a defect, so its retention time hops irregularly between two or more values. A cell that appears to have sufficient retention during testing may later get shorter, so margin is needed in refresh design and testing.

  • A. Correct. It is the irregular fluctuation of retention time.
  • B. A soft error is a temporary data flip caused by radiation or similar.
  • C. Row hammer is data flipping caused by frequently activating an adjacent row.
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