Abstract: A stacked memory chip includes a chip input-output pad unit, a first semiconductor die and a second semiconductor die. The chip input-output pad unit includes a chip command-address pad unit, a lower chip data pad unit and an upper chip data pad unit that are to be connected to an external device. The first semiconductor die electrically is connected to the chip command-address pad unit and the lower chip data pad unit and electrically disconnected from the upper chip data pad unit. The second semiconductor die electrically is connected to the chip command-address pad unit and the upper chip data pad unit and electrically disconnected from the lower chip data pad unit. The input-output load may be reduced by selectively connecting each of the stacked semiconductor dies to one of the lower chip data pad unit and the upper chip data pad unit.

Abstract: A semiconductor memory device includes a memory cell array and a refresh control circuit. The memory cell array includes a plurality of memory cell rows. The refresh control circuit performs a normal refresh operation on the plurality of memory cell rows and performs a weak refresh operation on a plurality of weak pages of the plurality of memory cell rows. Each of the weak pages includes at least one weak cell whose data retention time is smaller than normal cells. The refresh control circuit transmits a refresh flag signal to a memory controller external to the semiconductor memory device when the refresh control circuit performs the weak refresh operation on the weak pages in a normal access mode.

Abstract: A stacked memory chip includes a chip input-output pad unit, a first semiconductor die and a second semiconductor die. The chip input-output pad unit includes a chip command-address pad unit, a lower chip data pad unit and an upper chip data pad unit that are to be connected to an external device. The first semiconductor die electrically is connected to the chip command-address pad unit and the lower chip data pad unit and electrically disconnected from the upper chip data pad unit. The second semiconductor die electrically is connected to the chip command-address pad unit and the upper chip data pad unit and electrically disconnected from the lower chip data pad unit. The input-output load may be reduced by selectively connecting each of the stacked semiconductor dies to one of the lower chip data pad unit and the upper chip data pad unit.

Abstract: A printed circuit board (PCB) includes a base substrate including upper and lower surfaces, a plurality of solder ball pads separately formed on the lower surface of the base substrate in a radial direction and forming one or more radial pad groups, a plurality of first traces respectively connected to the plurality of solder ball pads and extending to an inside of the radial pad group, and a plurality of second traces respectively connected to the plurality of first traces and extending to an outside of the radial pad group.

Abstract: A semiconductor memory device includes a memory cell array and a refresh control circuit. The memory cell array includes a plurality of memory cell rows. The refresh control circuit performs a normal refresh operation on the plurality of memory cell rows and performs a weak refresh operation on a plurality of weak pages of the plurality of memory cell rows. Each of the weak pages includes at least one weak cell whose data retention time is smaller than normal cells. The refresh control circuit transmits a refresh flag signal to a memory controller external to the semiconductor memory device when the refresh control circuit performs the weak refresh operation on the weak pages in a normal access mode.

Abstract: A printed circuit board (PCB) includes a base substrate including upper and lower surfaces, a plurality of solder ball pads separately formed on the lower surface of the base substrate in a radial direction and forming one or more radial pad groups, a plurality of first traces respectively connected to the plurality of solder ball pads and extending to an inside of the radial pad group, and a plurality of second traces respectively connected to the plurality of first traces and extending to an outside of the radial pad group.

Abstract: A multi-chip package may include a system on a chip (SOC) and a plurality of memory devices arranged in the same layer on the SOC. Accordingly, as the multi-chip package may not need to use a TSV, so that manufacturing cost of the multi-chip package is reduced. Moreover, a memory bandwidth between the SOC and the first and second memory devices may increase.