External clock synchronization semiconductor memory device and method for controlling same
View Patent ↗An external clock synchronization SRAM 1 of one embodiment comprises a SRAM cell, a global digit line, a global precharge circuit, a D latch, and a global precharge control circuit. A delay circuit is disposed in the global precharge control circuit so that the precharge output of the global precharge circuit changes with a delay with respect to the clock signal supplied to the D latch.
1. An external clock synchronization semiconductor memory device in which each internal circuit operates according to a clock signal input from outside, comprising:
a memory cell;
a memory cell signal transmission line transmitting an output signal from the memory cell;
a precharge circuit precharging the memory cell signal transmission line;
a signal holding circuit fetching a signal transmitted by the memory cell signal transmission line according to a fetch control signal and outputting the fetched signal; and
a precharge control circuit conducting control so that a precharge output of the precharge circuit changes with a delay with respect to the fetch control signal.
2. The external clock synchronization semiconductor memory device according to claim 1 , wherein
the external clock synchronization semiconductor memory device has a single end configuration in which the output signal from the memory cell is transmitted by a single memory cell signal transmission line.
3. The external clock synchronization semiconductor memory device according to claim 2 , wherein
the signal holding circuit is a latch inputted with a clock signal as the fetch control signal; and
the precharge control circuit conducts control so that the precharge output of the precharge circuit changes with a delay with respect to the clock signal inputted to the latch.
4. The external clock synchronization semiconductor memory device according to claim 1 , wherein
the precharge control circuit comprises an OR logical circuit and a delay circuit connected to one input of the OR logical circuit.
5. The external clock synchronization semiconductor memory device according to claim 2 , wherein
the precharge control circuit comprises an OR logical circuit and a delay circuit connected to one input of the OR logical circuit.
6. The external clock synchronization semiconductor memory device according to claim 3 , wherein
the precharge control circuit comprises an OR logical circuit and a delay circuit connected to one input of the OR logical circuit.
7. The external clock synchronization semiconductor memory device according to claim 2 , wherein
the memory cell is a SRAM cell comprising a read circuit connected to a read digit line and a write circuit connected to a write digit line;
the read circuit comprises a CMOS inverter outputting a memory data signal;
the write circuit comprises a PMOS transistor and a NMOS transistor having gates thereof connected to the CMOS inverter output, and a control transistor connected between the drains of the PMOS transistor and NMOS transistor, the control transistor being OFF in an access period and ON in a non-access period, and wherein
the write digit line and the gate of the CMOS inverter of the read circuit are connected in the write circuit between the control transistor and the PMOS transistor.
8. The external clock synchronization semiconductor memory device according to claim 3 , wherein
the memory cell is a SRAM cell comprising a read circuit connected to a read digit line and a write circuit connected to a write digit line;
the read circuit comprises a CMOS inverter for outputting a memory data signal;
the write circuit comprises a PMOS transistor and a NMOS transistor having gates thereof connected to the CMOS inverter output, and a control transistor connected between the drains of the PMOS transistor and NMOS transistor, the control transistor being OFF in an access period and ON in a non-access period, and wherein
the write digit line and the gate of the CMOS inverter of the read circuit are connected in the write circuit between the control transistor and the PMOS transistor.
9. The external clock synchronization semiconductor memory device according to claim 1 , wherein
the external clock synchronization semiconductor memory device comprises a plurality of banks and a global digit line having the output of each bank connected thereto;
the signal holding circuit fetches and holds a signal transmitted by the global digit line; and
the precharge circuit precharges the global digit line.
10. The external clock synchronization semiconductor memory device according to claim 2 , wherein
the external clock synchronization semiconductor memory device comprises a plurality of banks and a global digit line having the output of each bank connected thereto;
the signal holding circuit fetches and holds a signal transmitted by the global digit line; and
the precharge circuit precharges the global digit line.
11. The external clock synchronization semiconductor memory device according to claim 3 , wherein
the external clock synchronization semiconductor memory device comprises a plurality of banks and a global digit line having the output of each bank connected thereto;
the signal holding circuit fetches and holds a signal transmitted by the global digit line; and
the precharge circuit precharges the global digit line.
12. The external clock synchronization semiconductor memory device according to claim 4 , wherein
the external clock synchronization semiconductor memory device comprises a plurality of banks and a global digit line having the output of each bank connected thereto;
the signal holding circuit fetches and holds a signal transmitted by the global digit line; and
the precharge circuit precharges the global digit line.
13. The external clock synchronization semiconductor memory device according to claim 5 , wherein
the external clock synchronization semiconductor memory device comprises a plurality of banks and a global digit line having the output of each bank connected thereto;
the signal holding circuit fetches and holds a signal transmitted by the global digit line; and
the precharge circuit precharges the global digit line.
14. The external clock synchronization semiconductor memory device according to claim 6 , wherein
the external clock synchronization semiconductor memory device comprises a plurality of banks and a global digit line having the output of each bank connected thereto;
the signal holding circuit fetches and holds a signal transmitted by the global digit line; and
the precharge circuit precharges the global digit line.
15. The external clock synchronization semiconductor memory device according to claim 7 , wherein
the external clock synchronization semiconductor memory device comprises a plurality of banks and a global digit line having the output of each bank connected thereto;
the signal holding circuit fetches and holds a signal transmitted by the global digit line; and
the precharge circuit precharges the global digit line.
16. The external clock synchronization semiconductor memory device according to claim 8 , wherein
the external clock synchronization semiconductor memory device comprises a plurality of banks and a global digit line having the output of each bank connected thereto;
the signal holding circuit fetches and holds a signal transmitted by the global digit line; and
the precharge circuit precharges the global digit line.
17. The external clock synchronization semiconductor memory device according to claim 1 , wherein
the external clock synchronization semiconductor memory device has a dual end configuration in which an output signal from the memory cell is transmitted by two memory cell signal transmission lines,
the memory device further comprising a sense amplifier for amplifying the signal on the two memory cell signal transmission lines, and wherein
the precharge circuit precharges the two memory cell signal transmission lines on the input side of the sense amplifier;
the signal holding circuit is connected to the output side of the sense amplifier; and
the precharge control circuit conducts control so that a precharge output of the precharge circuit changes with a delay with respect to an enable signal of the sense amplifier serving as the fetch control signal.
18. A control method for an external clock synchronization semiconductor memory device in which each internal circuit operates according to a clock signal input from outside, the control method comprising:
selecting a memory cell for outputting a signal;
fetching the selected memory cell output transmitted on a transmission line to a signal holding circuit and outputting the fetched signal as an output signal to the outside; and
precharging the transmission line after the fetching of a signal by the signal holding circuit is prohibited.
19. A control method for an external clock synchronization semiconductor memory device according to claim 18 , wherein
the signal holding circuit is a D latch and the transmission line is precharged with a delay with respect to the change of the input clock signal to the D latch.