Integrated Circuit Memory Devices Including a Plurality of Row Latch Circuits and Related Methods

1. Field of the Invention

The present invention relates to a semiconductor memory device. More particularly, it relates to a semiconductor memory device with multibank structure for the purpose of effectively activating and precharging word lines and bit lines.

The present application is based on Korean Application No. 30478/1995 which is incorporated herein by reference.

2. Description of the Related Art

In a central processing unit (CPU) and a memory, the more the number of banks of a dynamic random access memory (DRAM) increases, the more the number of word lines that can be kept in the active state increases. This may raise the page hit ratio of DRAM in case of cache miss thereby reducing the access time. In recent years, there has been a tendency to substitute a DRAM with increased banks in number for a static random access memory SRAM being used as a cache.

FIG. 1 depicts a conventional memory device with multibank structure.

As shown in FIG. 1, each one of four banks 0, 1, 2 and 3 consists of a memory cell array and a bit-line sense amplifier. Row address predecoders 10, 30, 60 and 80 are respectively provided to the banks 0, 1, 2 and 3. The row address predecoders 10, 30, 60 and 80 respectively have output lines 3, 5, 7 and 9. Column decoders 50, 51, 52 and 53 are assigned to each bank 0, 1, 2 and 3, too. Therefore, an increase in the number of the banks causes the size of a chip to be significantly increased, and it is hard to increase the banks in number.

FIG. 2 is a block diagram of a conventional semiconductor memory device with stacked multibank structure in which a plurality of banks have one row address predecoder and its output line in common.

Row address predecoders 10, 30, 60 and 80 and their respective output lines 3, 5, 7 and 9 are used in common for a bank group a (banks a1 to am), a bank group b (banks b1 to bm), a bank group c (banks c1 to cm), and a bank group d (banks d1 to dm). Regarding each word-line enabling/disabling operation and sensing operation of each bit-line sense amplifier, a bank activation in response to an active command of a preceding clock signal from an external system may be disabled by the following clock signal's precharge command given to another bank. Thus, the word-line precharging operation may be performed before the word line is disabled, or the corresponding bit-line sense amplifier may be actuated to perform the sensing operation before the word line is enabled.

Accordingly, it is an object of the present invention to provide a semiconductor memory device with improved multibank structure in which a row strobe buffer, a row address sampling circuit and a row decoder can effectively control word-line activating/precharging operations and operating time of bit-line sense amplifiers.

It is another object of the present invention to provide a semiconductor memory device with improved multibank structure in which a bit-line sensing enable control signal generating circuit and a row-address sampling control signal generating circuit can effectively control word-line activating/precharging operations and operating time of bit-line sense amplifiers.

In order to realize the above objects, a semiconductor memory device that has a memory-cell array with memory cells arranged in a matrix, bit-line sense amplifiers connected to bit lines of the memory-cell array, a row address predecoder performing decoding of some of row address signals in response to a system clock, and a plurality of banks having an output line of the row address predecoder in common, includes: a row strobe buffer connected to an external system and producing a first control signal for selecting corresponding banks in response to the system clock, a row address strobe signal, and a bank selection address signal and for controlling generation of a row address sampling control signal; a row address sampling control signal generating circuit producing the row address sampling control signal in a predetermined period of time in response to generation of the first control signal produced by the row strobe buffer in order to control word-line activating and precharging operations; and a row decoder latching an output signal obtained by decoding a row address with the output signal of the row address sampling control signal generating circuit.

As another aspect of the present invention, in addition to the above components, the inventive semiconductor memory device may include a circuit for controlling enabling and disabling of the bit-line sense amplifier in response to the first control signal, and producing the bit-line sensing enable control signal that is more delayed than the row address sampling control signal.

FIG. 1 is a block diagram of a conventional memory device with multibank structure;

FIG. 2 is a block diagram of another conventional semiconductor memory device with stacked multibank structure in which a plurality of banks have one row address predecoder and its output line in common;

FIG. 3 depicts a path for controlling a memory device with multibank structure in accordance with the present invention;

FIG. 4 is a block diagram of bank control signal generating circuits with multibank structure in accordance with the present invention;

FIG. 5 is a circuit diagram of a first control signal generating circuit of FIG. 4;

FIG. 6 is a circuit diagram of a row address sampling control signal generating circuit and a bit-line sensing enable control signal generating circuit of FIG. 4;

FIG. 7 is a circuit diagram of a row address sampling circuit and a row decoder of FIG. 4; and

FIG. 8 is a timing diagram of outputs of FIG. 3 at the time of row-activating/precharging the banks.

A preferred embodiment of the present invention is now described in detail with reference to the accompanying drawings. Similar reference numerals denote similar parts throughout the specification and drawings.

FIG. 3 depicts a path for controlling a memory device with multibank structure in accordance with the present invention.

As shown in FIG. 3, n banks b1 to bn arranged in the direction of length have a row address predecoder 30 and its output line 5 in common. A column decoder 51 controls the banks b1 to bn. Such a memory device includes row address sampling circuits and row decoders 10 to n0 that are under the control of the respective row address sampling control signals RADSABb1 to RADSABbn; bit-line sense amplifier driving circuits 11 to n1 which respectively generate N-sense amplifier driving signals LANGb1 to LANGbn and P-sense amplifier driving signals LAPGb1 to LAPGbn for controlling the operations of bit-line sense amplifiers of the banks b1 to bn by the control of bit-line sensing enable control signals SAEBb1 to SAEBbn; and word-line driving circuits 12 to n2 which respectively generate word-line driving signals WLi1 to WLin upon receipt of word-line enable driving signals WLEi1 to WLEin that are each output signals of the row address sampling circuits and row decoders 10 to n0.

A synchronous dynamic RAM may be synchronized at a rising edge of an external clock signal to give a row active command to one bank, and then may give a row precharge command to another bank in response to the following external clock signal. Besides, the synchronous dynamic RAM may give a row precharge command at a rising edge of an external clock signal.

As shown in FIG. 3, in case that a plurality of banks, e.g. the banks b1 to bn have in common the row address predecoder 30 and its output line 5, when a row precharge command is given to the bank b2 at the following clock after a row active command has been given to the bank b1, the sensing operation of the corresponding bit-line sense amplifier by the row active command given in response to the preceding clock signal becomes delayed, and the row precharging operation with respect to the other bank can be rapidly performed according to the row precharge command given by the following clock signal. In order to prevent one bank activation in response to the active command of the preceding clock signal from being disabled by the following clock signal's precharge command given to another bank, each bank individually latches an output of the row address predecoder 51 in the sampling method at the time of its row activation, and then generates a word line. Besides, each one of the banks has either a control signal RADSAB for precharging each row address sampling circuit and each row decoder at the time of precharge, or a signal SAEB for controlling the enabling/disabling of each bit-line sense amplifier at the time of its row activation or precharge.

FIG. 4 is a block diagram of bank control signal generating circuits with multibank structure in accordance with the present invention.

Referring to FIG. 4, the bank control signal generating circuits include row address sampling control signal generating circuits 10-1 to 10-n which respectively generate row address sampling control signals RADSABb1 to RADSABbn upon receipt of a first control signal PRb1; bit-line sensing enable control signal generating circuits 11-1 to 11-n that each produce bit-line sensing enable control signals SAEBb1 to SAEBbn upon receipt of the first control signal PRb1; and a row strobe buffer 100 that generates the first control signals PRb1 to PRbn in response to the generation of a complementary row address strobe signal RAS, a clock signal CLK from an external system, and bank selection address signals BAi (i=0-n).

The above circuits will be described in detail with reference to FIGS. 5, 6 and 7. FIG. 5 is a circuit diagram of the first control signal generating circuit of FIG. 4.

As shown in FIG. 5, the first control signal generating circuit includes an inverter chain 5 with even-numbered inverters for delaying the clock signal CLK for a pre-determined period of time and inverting it; NAND gates 10 and 20 that respectively perform a NAND operation with respect to a signal inverted from the complementary row address strobe signal RAS by an inverter 3; and an activation switch 80 which is coupled between external supply voltage Vcc and ground Vss, and has an output terminal connected to one of input terminals of the NAND gate 10 so as to be coupled to the external supply voltage Vcc at the time of activating a corresponding word line and to be coupled to the ground Vss at the time of precharging the word line for switching.

The first control signal generating circuit also includes a precharge switch 90 which is coupled between external supply voltage Vcc and ground Vss, and has an output terminal connected to one of input terminals of the NAND gate 20 so as to be coupled to the external supply voltage Vcc at the time of activating a corresponding word line and to be coupled to the ground Vss at the time of precharging the word line for switching; a NAND gate 30 that performs a NAND operation with respect to each input bank selection address signal BAi (i=0-n), and outputs a product to both the NAND gates 10 and 20 by way of an inverter 11; and PMOS transistors 40 and 50 and NMOS transistors 60 and 70 which are coupled in series between external supply voltage Vcc and ground Vss, and have their respective gate terminals connected to the NAND gate 10, the odd-numbered inverter of the inverter chain 5, the NAND gate 20, and the inverter chain 5.

The first control signal generating circuit further includes an inverter chain 7 that latches a signal produced to node n1 between the respective drain terminals of the PMOS transistor 50 and NMOS transistor 60, and an inverter 9 that inverts an output of the inverter chain 7 and produces the first control signal PRbi. The first control signal PRbi attains a logic "high" state at the time of activating a corresponding word line while it is at a logic "low" state at the time of precharging the word line.

FIG. 6 is a circuit diagram of the row address sampling control signal generating circuit and the bit-line sensing enable control signal generating circuit of FIG. 4.

As shown in FIG. 6, the first control signal PRbi is produced as the banks to be activated are determined, and is delayed for a predetermined period of time by the inverters 3 and 5. An inverted output of the first control signal PRbi is applied to one of input terminals of a NOR gate 50. The inverted output is also applied to an inverter chain 7 consisting of even-numbered inverters, and is then delayed for a predetermined period of time to be applied to the other input terminal of the NOR gate 50. The NOR gate 50 performs a NOR operation with respect to the delayed signal. An output signal produced by the NOR gate 50 is delayed by an inverter chain 13, and the inverter chain 13 produces a row address sampling control signal RADSABbi.

This bit-line sensing enable control signal generating circuit includes an inverter chain 9 with odd-numbered inverters for delaying and inverting the output signal of the inverter 5; an inverter chain 11 with even-numbered inverters for delaying an output signal of the inverter chain 9 for a predetermined period of time; a NOR gate 80 for outputting a logical product of each output signal of the inverter chains 9 and 11; and an inverter chain 15 for delaying for a predetermined period of time and inverting the output signal of the NOR gate 80 and for producing a bit-line sensing enable control signal SAEBbi.

The following description relates to the operation of the bit-line sensing enable control signal generating circuit.

In case of activating a corresponding word line, the first control signal PRbi attains a logic "high" state, and this high-level signal is delayed by the inverters 3 and 5 for a predetermined period of time. A high-level output signal of the inverter 5 is applied to the NOR gate 50. The high-level output signal of the inverter 5 is also applied to the inverter chain 7 and delayed thereby for a predetermined period of time. A high-level output signal inverted by the inverter chain 7 is produced to the NOR gate 50, and the NOR gate 50 performs a NOR operation with respect to the high-level output signal of the inverter chain 7 thereby producing a short pulse that attains a logic "low" state. The logic "low"-level signal is delayed by the inverter chain 13 for a predetermined period of time whereby the logic "low" row address sampling control signal RADSABbi is produced.

Further, the high-level output signal of the inverter 5 is applied to the inverter chain 9 and delayed thereby for a predetermined period of time. A high-level output signal of the inverter chain 9 is produced to the NOR gate 50, and is delayed thereby so that a logic "low"-level output signal can be produced to the inverter chain 11. An output of the inverter chain 11 attains a logic "low" state, and is produced to the NOR gate 80. The NOR gate 80 performs a NOR operation with respect to this "low"-level signal, and outputs a "high"-level signal. This "high"-level signal is then delayed for a predetermined period of time and inverted by the inverter chain 15. Therefore, the inverter chain 15 produces the bit-line sensing enable control signal SAEBbi which is at a logic "low" state.

The input first control signal attains a logic "low" state at the time of precharging a corresponding word line. Accordingly, the row address sampling control signal RADSABbi and the bit-line sensing enable control signal SAEBbi are each produced as logic "high"-level ones.

FIG. 7 is a circuit diagram of the row address sampling circuit and the row decoder of FIG. 4.

The row address sampling circuit 500 includes an inverter chain 3 which delays for a predetermined period of time and inverts the row address sampling control signal RADSABbi produced by the row address sampling control signal generating circuit of FIG. 6; a NOR gate 100 that receives the row address sampling control signal RADSABbi and an output signal of the inverter chain 3; and an inverter chain 5 which delays an output signal of the NOR gate 100 for a predetermined period of time.

In the meantime, the row decoder includes an inverter 7 which provides an output signal which is a negation of the input row address sampling control signal RADSABbi; a PMOS transistor 10 which receives the output signal of the inverter 7 through its gate terminal, and has a source terminal connected to external supply voltage Vcc and a drain terminal connected to node n2; and NMOS transistors 20, 30, 40 and 50 that are coupled in series between the node n2 and ground Vss, and respectively have gate terminals receiving row addresses DRAij, DRAk1 and DRAmn produced by the row address predecoder, and an output signal of the inverter chain 5.

The following description relates to the operation of the above circuits.

At the time of activating a corresponding word line, the row address sampling control signal RADSABbi attaining a logic "low" state is input to the row address sampling circuit 500. The signal is delayed for a predetermined period of time, and a short pulse attaining a logic "high" state is produced via the row address sampling circuit 500. When each of the row addresses DRAij, DRAk1 and DRAmn produced by the row address predecoder attains a logic "high" state, the NMOS transistors 20, 30, 40 and 50 are turned on, and the "high"-level signal is produced to the PMOS transistor 10 by the inverter 7. Accordingly, the PMOS transistor 10 is turned off so that the node n2 is at a logic "low" state.

The inverter chain 9 latches an output of the node n2 that attains a logic "low" state, and the inverter chain 11 delays for a predetermined period of time and inverts an output of the inverter chain 9 to produce a word-line enable control signal WLEi attaining a logic "high" state.

At the time of precharging the word line, the row address sampling control signal RADSABbi attaining a logic "high" state is input to the row address sampling circuit 500. The row address sampling circuit 500 is turned on to produce a "low"-level signal to the NMOS transistor 50. The NMOS transistor 5 is turned off, and the "low"-level signal inverted and produced by the inverter 7 is input to the PMOS transistor 10 so that the PMOS transistor 10 is turned on. Therefore, the node n2 attains a logic "low" state which results from a difference between the external supply voltage Vcc and threshold voltage of the PMOS transistor 10. The inverter chain 9 latches an output of the node n2 that attains a logic "high" state, and the inverter chain 11 delays for a predetermined period of time and inverts an output of the inverter chain 9 to produce a word-line enable control signal WLEi attaining a logic "low" state.

FIG. 8 is a timing diagram of outputs of FIG. 3 in accordance with the present invention at the time of row activating/precharging the banks.

The reference letter CLK denotes a system clock signal and the row address sampling control signals RADSABb1 and RADSABb2 are enabled to attain logic "low" states each by the first control signals PRb1 and PRb2 in response to row active commands of clock signals 2 and 3 so that a valid row address is produced to the output line of the row address predecoder. Subsequently, a pulse attaining a logic "high" state is produced by the row address sampling circuit 500 of FIG. 7 to make the corresponding word-line enable control signal WLEi attain a logic "high" state so that the corresponding address' word line is at a logic "high" state.

Responding to the clock signals 2 and 3, bit-line sensing enable signals SAEBb1 and SAEBb2 are more delayed than the signal WLEi by the signals PRb1 and PRb2, and are enabled to be at logic "low" states each to make the N/P sense amplifier driving signals LANG and LAPG be at logic "high" and "low" states each thereby starting the sensing action.

When a row precharge command is given in response to clock signals 1 and 4, each first control signal PRb1 and PRb2 attains a logic "low" state, and each one of the signals PADSABb1 and PADSABb2 becomes at a logic "high" state by these signals PRb1 and PRb2 so that the row decoder is precharged to a logic "high" level. Each signal WLEi1 and WLEi2 is disabled to be at a logic "low" state, and the corresponding word line WLi becomes disabled to be at a logic "low" state. Besides, each bit-line sensing enable signal SAEBb1 and SAEBb2 attains a logic "high" state by the "low"-level first control signals PRb1 and PRb2, and the N/P sense amplifier driving signals LANG and LAPG are at logic "low" and "high" states each thereby disabling the bit-line sense amplifier.

In accordance with the present invention, a semiconductor memory device in which a plurality of the banks have one row address predecoder and its output line in common, may effectively control the word-line activating/precharging operations and the operating time of bit-line sense amplifiers, thereby ensuring a reduction in the access time.

Therefore, it should be understood that the present invention is not limited to the particular embodiment disclosed herein as the best mode contemplated for carrying out the present invention, but rather that the present invention is not limited to the specific embodiments described in this specification except as defined in the appended claims.