Termination control circuit and method for global input/output line

A termination control circuit for a global input/output line includes a speed determination unit configured to output a termination enable signal which is activated in response to a frequency of an external clock signal and CAS latency information; and a pulse generation unit configured to output a driving signal for driving a termination circuit for the global input/output line in response to a termination control signal and the termination enable signal.

CROSS-REFERENCES TO RELATED PATENT APPLICATION

The present application claims priority under 35 U.S.C 119(a) to Korean Application No. 10-2008-0136384, filed on Dec. 30, 2008, in the Korean Intellectual Property Office, which is incorporated herein by reference in its entirety as set forth in full.

BACKGROUND

1. Technical Field

The embodiment described herein relates to a semiconductor memory apparatus and, more particularly, to a termination control circuit and a termination control method for a global input/output line.

2. Related Art

A semiconductor memory apparatus is desired to operate at a high frequency, a high speed, and a low voltage. The speed of the semiconductor memory apparatus depends on a data access time (tAA). The data access time means a time until a first datum is outputted after a read command is inputted.

It is important to reduce a state transition time of a global input/output line GIO and a coupling noise in order to decrease the data access time. For this, a GIO termination circuit is used.

FIG. 1is a block diagram of a known semiconductor memory apparatus and illustrates some of constituent members for outputting data by the read command.

Data ‘IN’ read from a memory cell by a column selection signal are inputted into a read driver10through a local input/output line LIO. Further, the data ‘IN’ are transmitted to a receiver14through a global input/output (GIO) line and output data ‘OUT’ of the receiver14are outputted through a data pad (not shown). At this time, a GIO termination circuit12is provided in each GIO line in order to shorten a transition time of the GIO line. Further, the GIO line is precharged by driving the GIO termination circuit12with a termination control signal ‘WTS’ that is enabled response to the read command.

FIG. 2is a circuit diagram of the semiconductor memory apparatus ofFIG. 1.

First, the read driver10is constituted by an inverter that is connected between a power supply voltage terminal VDD and a ground terminal VSS to receive and inversely output the data ‘IN’. Herein, the inverter can be configured by connecting a first PMOS transistor P11and a first NMOS transistor N11in series.

The GIO termination circuit12can be configured to include a second PMOS transistor P12of which a source terminal is connected to the power supply voltage terminal VDD and a gate terminal is applied with the termination control signal ‘WTS’, a third PMOS transistor P13of which a source terminal is connected to a drain terminal of the second PMOS transistor P12, and a gate terminal and a drain terminal are commonly connected, and a first resistance element R11that is connected between the drain terminal of the third PMOS transistor P13and an output terminal of the read driver10.

In addition, the GIO termination circuit12can be configured to include a third NMOS transistor N13of which a gate terminal is applied with an inversion signal of the termination control signal ‘WTS’ and a source terminal is connected to the ground terminal VSS, a second NMOS transistor N12of which a source terminal is connected to a drain terminal of the third NMOS transistor N13, and a drain terminal and a gate terminal are commonly connected, and a second resistance element R12that is connected between the drain terminal of the second NMOS transistor N12and the output terminal of the read driver10.

Moreover, the receiver14is constituted by an inverter that is connected between the power supply voltage terminal VDD and the ground terminal VSS to generate the output data OUT by inverting an output signal of the read driver10. Herein, the inverter can be configured by a fourth PMOS transistor P14and a fourth NMOS transistor N14that are connected between the power supply voltage terminal VDD and the ground terminal VSS in series.

The termination control signal ‘WTS’ has a logically high state in a write command and a logically low state in the read command. The termination control signal WTS controls on/off states of the GIO termination circuit12.

When the read command is generated, the termination control signal WTS is transitioned to a low level. The second PMOS transistor P12and the third PMOS transistor P13are turned on to precharge the GIO line before the input data ‘IN’ are transmitted to the GIO line.

As such, by driving the GIO termination circuit12to reduce a swing width of the GIO line in a read operation, a signal can be transmitted at a high speed and the coupling noise of adjacent GIO lines can be reduced. On the contrary, unnecessary current consumption is prevented by turning off the GIO termination circuit12in a write operation.

However, the GIO termination circuit12must be provided in each GIO line. For example, a semiconductor memory apparatus operating at a speed of ×16 uses 64 GIO lines and thus needs 64 GIO termination circuits.

In the GIO termination circuit12shown inFIG. 2, a current path is formed by the second PMOS transistor P12, the third PMOS transistor P13, and the first NMOS transistor N11in the read operation. A current used in the GIO termination circuit12increases in proportion to the number of GIO termination circuits12.

As a result, an active-read-precharge current IDD1and a burst-read current IDD4R increase, such that power consumption increases.

SUMMARY

A termination control circuit and a termination control method for a global input/output line that can determine termination or not of the global input/output line depending on an operation speed of the semiconductor memory apparatus are disclosed herein.

A termination control circuit and a termination control method for a global input/output line that can prevent unnecessary current consumption by turning off a termination circuit for the global input/output line in a semiconductor memory apparatus that does not operate at a certain speed are also disclosed herein.

In one aspect, a termination control circuit for a global input/output line includes a speed determination unit configured to output a termination enable signal which is activated in response to a frequency of an external clock signal and CAS latency information; and a pulse generation unit configured to output a driving signal for driving a termination circuit for the global input/output line in response to a termination control signal and the termination enable signal.

In another aspect, a termination control method for a global input/output line includes determining whether or not a frequency of an external clock signal and CAS latency information satisfy a certain combination in response to receipt of the external clock signal and the CAS latency information are inputted; and outputting a driving signal for driving a termination circuit for a global input/output line when the frequency of the external clock signal and the CAS latency information satisfy the certain combination.

These and other features, aspects, and embodiments are described below in the section “Detailed Description.”

DETAILED DESCRIPTION

FIG. 3is a block diagram of an exemplary semiconductor memory apparatus with a termination control circuit according to one embodiment. In particular,FIG. 3illustrates exemplary constituent members for outputting data by a read command.

As shown in the figure, the semiconductor memory apparatus can include a termination control circuit100, a read driver200, a GIO termination circuit300, and a receiver400.

First, the termination control circuit100can determine an operation speed of the semiconductor memory apparatus in accordance with a frequency of an external clock signal ‘CLK’ and CAS latency (CL) information ‘CL<1:n>’. Further, when a certain speed is satisfied, the termination control circuit100can output a driving signal ‘EN’ for turning on the GIO termination circuit300in response to a termination control signal ‘WTS’.

The read driver200receives data ‘IN’ read from a memory cell through an LIO line in accordance with a read command.

Meanwhile, the GIO termination circuit300is driven by the driving signal ‘EN’ to precharge the GIO line before the data are outputted from the read driver200.

Moreover, the receiver400can receive the data transmitted through the GIO line and generate output data ‘OUT’.

Herein, the GIO termination circuit300may be configured according to an example shown inFIG. 2, but is not limited thereto.

Hereinafter, the termination control circuit100will be described below in detail. The termination control circuit100can detect a frequency by receiving the external clock signal ‘CLK’ and determine whether or not the operation speed of the semiconductor memory apparatus satisfies the certain speed by combining information on the detected frequency with the CAS latency information given from a mode register set (MRS).

A data access time (tAA) for determining the operation speed of the semiconductor memory apparatus is acquired by multiplying the CAS latency by the clock signal frequency. For example, when the clock signal frequency is 400 MHz, one cycle is 2.5 ns and when the CAS latency (CL) is 5, the data access time (tAA) is 2.5 ns×5=12.5 ns.

Therefore, in the present invention, a combination of the external clock signal frequency and the CAS latency are previously determined in order to drive the GIO termination circuit300. When a combination of the external clock signal frequency and the CAS latency information received from the MRS satisfies the certain combination, the GIO termination circuit300is driven.

That is, the external clock signal frequency is detected and at this time, when the CAS latency (CL) information acquired from the MRS is inputted as a value satisfying a condition for a high-speed operation of the semiconductor memory apparatus, the termination control circuit100outputs the driving signal ‘EN’ for turning on the GIO termination circuit300.

FIG. 4is a configuration diagram of an exemplary termination control circuit ofFIG. 3according to one embodiment.

InFIG. 4, the termination control circuit100can include a speed determination unit110and a pulse generation unit120.

The speed determination unit110can determine whether or not the semiconductor memory apparatus operates at a high speed in response to the external clock signal ‘CLK’ and the CAS latency (CL) information. Further, when it is determined that the semiconductor memory apparatus operates at the high speed, a termination enable signal ‘ENTERM’ is activated.

For this, the speed determination unit110can include a frequency detection portion112and a comparison portion114.

First, the frequency detection portion112receives the external clock signal ‘CLK’ and detects the frequency of the external clock signal ‘CLK’ to output an n-bit frequency detection signal ‘D<1:n>’. Herein, the frequency detection signal ‘D<1:n>’ has a high level in only one bit thereof in accordance with a frequency detection result. For example, n may be 3, and a first frequency detection signal ‘D<1>’ when the frequency is 533 MHz, a second frequency detection signal ‘D<2>’ when the frequency is 400 MHz, and a third frequency detection signal ‘D<3>’ when the frequency 333 MHz may be outputted at a high level.

Herein, the frequency detection portion112may be configured in various forms. For example, when a reference clock is set, the frequency detection portion112counts the number of cycles which the external clock signal ‘CLK’ has for one cycle of the reference clock signal and outputs the frequency detection signal by decoding the result.

Next, the comparison portion114can activate the terminal enable signal ‘ENTERM’ by receiving a frequency detection signal ‘D<1:n>’, which is outputted from the frequency detection portion112and CAS latency information ‘CL<1:n>’, which is given from the MRS. At this time, the comparison portion114can activate the termination enable signal ‘ENTERM’ when it is determined that the semiconductor memory apparatus operates at the high speed in accordance with the combination of the frequency of the external clock signal and the CAS latency (CL) configured to satisfy the condition for the high-speed operation of the semiconductor memory apparatus.

Meanwhile, the pulse generation unit120can output the driving signal ‘EN’ for controlling on/off states of the GIO termination circuit300by receiving the termination enable signal ‘ENTERM’ and the termination control signal ‘WTS’.

FIG. 5is a circuit diagram of an exemplary comparison portion ofFIG. 4according to one embodiment.

In regard to a condition for driving the GIO termination circuit300, that is, the certain combination of the external clock signal frequency of the semiconductor memory apparatus and the CAS latency (CL), the comparison portion114can determine whether or not the semiconductor memory apparatus satisfies the certain combination by comparing the CAS latency (CL) information acquired from the MRS with the frequency detected from the frequency detection portion112.

For this, the comparison portion114can include a plurality of NAND gates ND1to ND3that each receives a bit of the frequency detection signal ‘D<1:n>’ and a bit of the CAS latency information ‘CL<1:n>’, a plurality of inverters IV1to IV3that are connected to output terminals of the NAND gates ND1to ND3, and logical elements NR1and IV4that combine signals outputted from the plurality of inverters IV1to IV3.

More specifically, the first NAND gate ND1can receive the first frequency detection signal ‘D<1>’ and first CAS latency information ‘CL<1>’ and the first inverter IV1can invert an output signal of the first NAND gate ND1. The second NAND gate ND2can receive the second frequency detection signal ‘D<2>’ and second CAS latency information ‘CL<2>’ and the second inverter IV2can invert an output signal of the second NAND gate ND2. Moreover, the third NAND gate ND3can receive the third frequency detection signal ‘D<3>’ and third CAS latency information ‘CL<3>’ and the third inverter IV3can invert an output signal of the third NAND gate ND3.

A NOR gate NR1constituting the logical element can receive output signals of the first to third inverters IV1, IV2, and IV3. The fourth inverter IV4can output the termination enable signal ‘ENTERM’ by inverting an output signal of the NOR gate NR1.

The comparison portion114shown inFIG. 5receives the 3-bit frequency detection signal ‘D<1:3>’ and the 3-bit CAS latency information ‘CL<1:3>’, but is not limited thereto.

Any one of the frequency detection signals ‘D<1:n>’ is outputted at a high level by the frequency detection portion112and any one of the CAS latency information ‘CL<1:n>’ is inputted at a high level by the CAS latency (CL) acquired from the MRS.

The comparison portion114can output the termination enable signal ‘ENTERM’ at a high level when any one frequency detection signal is inputted at a high level and the CAS latency information acquired from the MRS satisfies the certain combination of the external clock signal frequency and the CAS latency (CL) information.

For example, when the external clock signal frequency is 533 MHz, the first frequency detection signal ‘D<1>’ is outputted at a high level. In this case, when the first CAS latency information ‘CL<1>’ indicating that the CAS latency6is at a high level, it is determined that the semiconductor memory apparatus operates at the high speed.

Similarly, when the external clock signal frequency is 400 MHz, the second frequency detection signal ‘D<2>’ is outputted at a high level. In this case, when the second CAS latency information ‘CL<2>’ indicating that the CAS latency5is at a high level, it is determined that the semiconductor memory apparatus operates at the high speed. Further, when the external clock signal frequency is 333 MHz, the third frequency detection signal ‘D<3>’ is outputted at a high level. In this case, when the third CAS latency information ‘CL<3>’ indicating that the CAS latency4is at a high level, it is determined that the semiconductor memory apparatus operates at the high speed.

That is, when the combination of the external clock signal frequency and the CAS latency information satisfies the certain combination, the termination enable signal ‘ENTERM’ is outputted at a high level.

FIG. 6is a configuration diagram of an exemplary pulse generation unit ofFIG. 4according to one embodiment.

The pulse generation unit120can include a fourth NAND gate ND4that can output the driving signal ‘EN’ by receiving the termination enable signal ‘ENTERM’ generated by the comparison portion114and a termination control signal ‘/WTS’ inverted by a fifth inverter IV5.

When the combination of the external clock signal frequency of the semiconductor memory apparatus and the CAS latency (CL) satisfies the certain combination, such that it is determined that the semiconductor memory apparatus operates at the high speed, the terminal enable signal ‘ENTERM’ is outputted at a high level and when the termination control signal ‘WTS’ is at a low level by the read operation, the fourth NAND gate ND4can turn on the GIO termination circuit300by outputting the driving signal ‘EN’ having the low level.

On the contrary, when the combination of the external clock signal frequency of the semiconductor memory apparatus and the CAS latency (CL) does not satisfy the certain combination, the termination enable signal ‘ENTERM’ is outputted at a low level. In this case, even though the termination control signal ‘WTS’ is at a low level, the driving signal ‘EN’ is at a high level, such that the GIO termination circuit300is turned off.

According to the present invention, it is possible to prevent unnecessary current consumption by driving a GIO termination circuit300only when a combination of an external clock signal frequency of the semiconductor memory apparatus and CAS latency (CL) satisfies a certain combination by considering the external clock signal frequency and the CAS latency.