Semiconductor memory device
View Patent ↗A semiconductor memory device includes a plurality of memory cells that are arranged at intersections of a word line with bit line pairs, a precharge circuit that is arranged for each of the bit line pairs and is configured to precharge each of the bit line pairs, and a Y-switch circuit that is arranged for each of the bit line pairs and is configured to select each of the bit line pairs. The semiconductor memory device further includes a mode switching unit that switches the normal mode and the test mode in accordance with a mode selection signal that is externally supplied, a plurality of individual control units that control operation of each of the precharge circuits in accordance with operation of each of the Y-switch circuits in the normal mode, and a block control unit that collectively turns off all of the precharge circuits in the test mode.
1. A semiconductor memory device comprising:
a plurality of memory cells that are arranged at intersections of a word line with bit line pairs;
a precharge circuit that is arranged for each of the bit line pairs, the precharge circuit being configured to precharge each of the bit line pairs; and
a Y-switch circuit that is arranged for each of the bit line pairs, the Y-switch circuit being configured to select each of the bit line pairs, wherein
the semiconductor memory device is configured to execute two modes of a normal mode and a test mode by switching the two modes, the normal mode being a mode that executes reading or writing of normal memory data, the test mode being a mode that is capable of executing long write on a memory cell which is a test target, the semiconductor memory device further comprising:
a mode switching unit that switches the normal mode and the test mode in accordance with a mode selection signal that is externally supplied;
a plurality of individual control units that control operation of each of the precharge circuits in accordance with operation of each of the Y-switch circuits in the normal mode; and
a block control unit that turns off all of the precharge circuits by a command by a block selection signal in the test mode.
2. The semiconductor memory device according to claim 1 , wherein
in the normal mode,
upon selection of a bit line pair which is connected to a memory cell which is a reading target or a writing target of memory data by each of the Y-switch circuits,
each of the individual control units turns off the precharge circuit connected to the bit line pair which is selected by the Y-switch circuit and keeps an ON state of a precharge circuit connected to a bit line pair which is not selected by the Y-switch circuit in accordance with the operation of the Y-switch circuit that performs the selection operation.
3. The semiconductor memory device according to claim 1 , comprising:
a unifying NAND circuit that receives two inputs of the mode selection signal and the block selection signal and outputs an inverted logical AND of the two inputs to a block control line that is horizontally arranged between all the precharge circuits and the Y-switch circuits; and
a plurality of individual NAND circuits, each of which including two inputs and one output, one of the two inputs being an output of the unifying NAND circuit and the other of the two inputs being an operation signal of each Y-switch circuit, the output being a control signal of each precharge circuit, wherein
the mode switching unit and the block control unit are formed by the unifying NAND circuit; and
the individual control units are formed of the individual NAND circuits.
4. The semiconductor memory device according to claim 3 , wherein the operation signal of the Y-switch circuit which is the other input of the individual NAND circuit is a signal that is obtained by inverting a selection signal that operates the Y-switch circuit.
5. The semiconductor memory device according to claim 1 , wherein the memory cell is a static memory cell.