US20040264272A1 - Method and apparatus for accelerating signal equalization between a pair of signal lines - Google Patents
Method and apparatus for accelerating signal equalization between a pair of signal lines Download PDFInfo
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- US20040264272A1 US20040264272A1 US10/855,410 US85541004A US2004264272A1 US 20040264272 A1 US20040264272 A1 US 20040264272A1 US 85541004 A US85541004 A US 85541004A US 2004264272 A1 US2004264272 A1 US 2004264272A1
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/21—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements
- G11C11/34—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices
- G11C11/40—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors
- G11C11/401—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors forming cells needing refreshing or charge regeneration, i.e. dynamic cells
- G11C11/4063—Auxiliary circuits, e.g. for addressing, decoding, driving, writing, sensing or timing
- G11C11/407—Auxiliary circuits, e.g. for addressing, decoding, driving, writing, sensing or timing for memory cells of the field-effect type
- G11C11/409—Read-write [R-W] circuits
- G11C11/4091—Sense or sense/refresh amplifiers, or associated sense circuitry, e.g. for coupled bit-line precharging, equalising or isolating
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C7/00—Arrangements for writing information into, or reading information out from, a digital store
- G11C7/12—Bit line control circuits, e.g. drivers, boosters, pull-up circuits, pull-down circuits, precharging circuits, equalising circuits, for bit lines
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C2207/00—Indexing scheme relating to arrangements for writing information into, or reading information out from, a digital store
- G11C2207/12—Equalization of bit lines
Definitions
- the present invention relates generally to a system and method for improving bit line equalization in a semiconductor memory.
- DRAM dynamic random access memory
- bit line equalization and pre-charge portion of a DRAM row access cycle represents operational overhead that increases the average latency of memory operations and reduces the rate at which row accesses can be performed. Part of the difficulty in reducing this latency is due to typical DRAM architectures, which maximize memory capacity per unit area by favouring large DRAM cell arrays. Large DRAM cell arrays require long bit lines, which are highly capacitive. Thus, the bit lines require a relatively large amount of current to quickly change the voltage on them, as described in U.S. Pat. No. 5,623,446 issued Hisada et al.
- Hisada et al. describe a system for providing semiconductor memory with a booster circuit.
- the booster circuit boosts the voltage on the gates of the precharge and equalize devices during a selected portion of time in an attempt to decrease the precharge time.
- this approach requires higher power, which is undesirable for many applications.
- Lee describes a semiconductor device wherein the memory in segmented into components and adjacent memories share a sense amplifier.
- the semiconductor includes a blocking circuit for blocking bit lines associated with the memory component not in use.
- the semiconductor is capable of reducing the bit line precharge time, by improving the operation of the blocking circuits.
- this approach runs into fundamental limitations regarding how much the bit line equalization period can be shortened due to the distributed resistive and capacitive parasitic characteristics of the bit line material.
- a first class comprises bank accesses. Bank accesses require full row or column access in order to access a memory location.
- a second class comprises page accesses. Page accesses are typically faster than bank accesses and only require column access to a row that has been left open from a previous bank operation.
- the efficacy of page accesses in reducing average latency is due to the statistical spatial locality in the memory access patterns of many computing and communication applications. That is, there is a strong probability that consecutive memory accesses will target the same row.
- this architecture is undesirable for many applications such as real time control and digital signal processing that value deterministic, or at least minimum assured levels of memory performance regardless of the memory address access pattern.
- One solution is to perform a complete row and column access for every memory operation and automatically close the row at the end of the operation.
- RC distributed resistive-capacitive
- An equalization circuit in accordance with the invention comprises a pair of data lines having a first end and a second end.
- a first equalizing element is operatively coupled between the pair of data lines.
- the first equalizing element is located proximate to the first end of the pair of data lines.
- a precharging element for precharging the pair of data lines to a precharge voltage level is operatively coupled between the pair of data lines and is positioned proximate to the first equalizing element.
- a second equalizing element is operatively coupled between the pair of data lines. The second equalizing element is positioned along the pair of data lines in spaced apart relation to the first equalizing element.
- the additional equalization element located along the data line allows faster precharge and equalization operations.
- FIG. 1 a is a schematic diagram of memory array circuit (prior art).
- FIG. 1 b is a schematic diagram of an alternate embodiment of the memory array circuit illustrated in FIG. 1 a (prior art);
- FIG. 2 a is a schematic diagram of a bit line pair illustrated in FIGS. 1 a and 1 b (prior art);
- FIG. 2 b is a schematic diagram of an equivalent model of the bit line pair illustrated in FIG. 2 a (prior art)
- FIG. 3 a is a schematic diagram of a memory array circuit in accordance with an embodiment of the present invention.
- FIG. 3 b is a schematic diagram of an alternate embodiment of the memory array circuit illustrated in FIG. 3 a;
- FIG. 4 a is a schematic diagram of a bit line pair illustrated in FIGS. 3 a and 3 b;
- FIG. 4 b is a schematic diagram of equivalent model of the bit line pair illustrated in FIG. 4 a;
- FIG. 5 a is a schematic diagram of yet an alternate embodiment of the memory array circuit illustrated in FIG. 3 a ;
- FIG. 5 b is a schematic diagram of an alternate embodiment of the memory array circuit illustrated in FIG. 5 a.
- FIG. 1 a a bit line precharge and equalization circuit illustrating a prior art DRAM architecture is illustrated generally by numeral 100 .
- the circuit 100 comprises a memory cell array 101 , having memory cells located at the intersection of ones of a plurality bit line pairs 102 and word lines 108 .
- Each bit line pair 102 is comprised of a first or true bit line 102 a and a second line or complementary bit line 102 b .
- a sense amplifier 104 is operatively coupled between the true bit line 102 a and the complementary bit line 102 b at one end of the bit line pair 102 .
- a precharge equalization circuit 106 is also operatively coupled between the true bit line 102 a and the complementary bit line 102 b at the same end of the bit line pair 102 as the sense amplifier 104 .
- Memory cell access transistors 105 are located at word line 108 and bit line 102 intersections for accessing the memory cells.
- the sense amplifier 104 and the precharge circuit 106 are arranged in circuit 100 to be located together on the same side of the memory cell array for each bit line pair. Alternately, the sense amplifier 104 and the precharge and equalization circuit 106 may be located together on opposite sides of the memory of cell array for adjacent bit line pairs, as shown in FIG. 12 b . Furthermore, the sense amplifier 104 and the precharge and equalization circuit 106 may also be located separately on opposite sides of the memory cell array for each bit line pair (not shown).
- bit line precharge and equalization is performed by the precharge circuit 106 .
- the precharge and equalization circuit 106 comprises three n-channel transistors N 1 , N 2 , and N 3 .
- the drain and the source of transistor N 1 are operatively coupled between the true bit line 102 a and the complementary bit line 102 b of the bit line pair 102 .
- the gate of the equalization transistor N 1 is operatively coupled to an equalization enable line 110 .
- the drain of transistor N 2 is connected to the true bit line 102 a of the bit line pair.
- the source of N 2 is connected to both the drain of N 3 and a bit line precharge voltage V blp 112 .
- the source of N 3 is operatively coupled with the complementary bit line 102 b of the bit line pair 102 .
- the gates for both N 2 and N 3 are operatively coupled with the equalization line 110 .
- Transistor N 1 equalizes the voltage on the associated true 102 a and complimentary 102 b bit lines, while transistors N 2 and N 3 drive the true 102 a and complimentary 102 b bit lines respectively to the precharge voltage level.
- the bit line sense amplifiers 104 sense the voltage difference between the true 102 a and complimentary 102 b bit lines induced from a read out of an associated charge within an accessed memory cell.
- the sense amplifier 104 amplifies the voltage difference until the bit line with the higher voltage is raised to approximately the positive supply voltage rail V dd while the bit line with the lower voltage is pulled to approximately the ground supply voltage rail V ss .
- the bit line precharge voltage V blp 112 is set close to midway between V dd and V ss .
- transistor N 1 is needed for the precharge voltage because the precharged voltage can be achieved by charge sharing between the true 102 a and complimentary 102 b bit lines when the two are shorted together through N 1 .
- leakage, capacitive coupling, asymmetries in bit line capacitance, and other effects require some current to be supplied through transistors N 2 and N 3 for restoring the bit line pair 102 to the bit line precharge voltage V blp 112 .
- FIG. 2( a ) a circuit diagram of a bit line pair 102 is shown generally by the numeral 200 .
- the circuit 200 includes the precharge circuit 106 as well as the memory cell access transistors 105 .
- the precharge and equalization circuitry that is transistors N 1 , N 2 , and N 3 , is located at one end of the bit line pair 102 .
- the bit lines have significant distributed RC parasitic characteristics due to the small width of bit lines 102 .
- the bit lines are typically placed as close together as possible in order to achieve a high memory density thus the width of the bit lines is at a minimum, or near minimum value.
- the memory cell access transistors 105 attached to the bit lines have an associated drain-capacitance that adds to the distributed RC parasitic characteristics.
- the RC parasitic characteristics cause an increase in the time required to equalize the bit line pair 102 . Therefore, the time needed to equalize and precharge a bit line pair is approximately proportional to the square of the bit line's length within the memory array.
- FIG. 2 b an equivalent model to the circuit illustrated in FIG. 2 a is shown generally by the numeral 250 .
- the equivalent model 250 illustrates the resistive and capacitive elements in the memory cell array as resistors and capacitors equivalent to the resistance and capacitance presented by the actual circuit.
- a circuit for reducing the time required for precharging a bit line pair is illustrated generally by the numeral 300 .
- the circuit includes a plurality of bit line pairs 102 , word lines 108 , memory cell access transistors 105 , and a sense amplifier 104 and a precharge circuit 106 located at one end of each bit line pair 102 .
- the circuit 300 further includes an additional transistor N 4 302 located at an end of the bit line pair opposite to the sense amplifier 104 and the precharge and equalization circuit 106 .
- the drain of transistor N 4 is coupled to the true 102 a bit line and the source of N 4 is coupled to the complimentary 102 b bit line.
- the gate of N 4 is coupled to an equalization enable line 110 .
- the addition of transistor N 4 effectively halves the length of the bit line as far as the RC delay is concerned and reduces the time needed to perform bit line equalization and precharge time. Typically the equalization and precharge time is reduced by approximately 75% as compared to prior art circuits.
- the location of transistor N 4 is more important than the extra drive that it provides.
- the addition of at least one extra equalization transistor along a bit line pair ensures that the distributed capacitance of the bit line pair and the associated memory cell transistors is more readily overcome with the additional drive provided by the extra equalization transistor(s).
- additional area required to implement the extra equalization transistor(s) per bit line pair is readily compensated by the resulting decrease in precharge and equalization timing. This timing decrease, in turn, greatly decreases the overall delay between memory accesses, thereby providing an embedded memory implementation its main advantage over discrete commodity memory implementations.
- an alternate embodiment of the above-described circuit is represented generally by the numeral 350 .
- a bit line pair including memory cell access transistors 105 is shown generally by the numeral 400 .
- an equivalent circuit to that of the physical circuit illustrated in FIG. 4( a ) is shown generally by the numeral 450 .
- the equivalent circuit 450 provides a model illustrating the resistive and capacitive elements in the memory cell array as well as the fact that each transistor N 1 and N 4 is only responsible for equalizing and precharging half the length of the bit line pair. As a result, the delay associated with the precharge and equalize operation becomes proportional to one quarter (1 ⁇ 4) the bit line length squared, i.e. delay ⁇ (bit line length) 2 .
- FIGS. 5 a and 5 b further alternate embodiments of bit line pair circuits are illustrated generally by the numerals 500 and 550 , respectively.
- the additional bit line equalization transistor N 4 is placed in the middle of the memory cell array.
- the size of transistor N 1 may be greatly reduced because it is only needed to compensate for the capacitance of the sense amplifier and column access devices.
- the central location of transistor N 4 is sufficient to cut the effective length of the distributed RC delay of the bit line pair 102 in half, thus allowing the size of transistor N 1 to be reduced.
- the equalizing effect of transistor N 4 is felt on both sides of the bit line pair due to its central location.
- the equalization effect of transistor N 1 is decreased compared to the case where transistor N 4 is located at the opposite end of the bit line pair. That is, N 1 can be decreased in size.
- the placement of the additional bit line equalization transistor N 4 may also be staggered with each adjacent bit line pair due to the tight spacing within the middle of the array (not shown). By staggering it is meant that the equalization transistors N 4 are placed to the left and right of the halfway point for adjacent bit line pairs.
- the sense amplifier and precharge and equalization transistors N 1 , N 2 and N 3 are preferably positioned on the same side as the position of the N 4 device, but at the end of the array. This staggered configuration can be used such that the space between bit line pairs does not have to be increased. If the additional bit line equalization transistors N 4 were placed directly below each other, the spacing requirements between bit line pairs would increase.
- the invention can be applied to other situations where long pairs of data lines are used to transmit data either differentially or dual rail, and the signal pair is equalized between transmission of data items.
- Such systems include high performance SRAMs, other types of electronic memories that are arranged in arrays, and long, high fan-out data buses within the data paths of digital signal processors and microprocessors.
- n-channel transistors are used in the above description, it will be apparent to a person skilled in the art to use p-channel transistor. Furthermore, although the invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art without departing from the spirit and scope of the inventions as outlined in the claims appended hereto.
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Abstract
A circuit is provided for equalizing a signal between a pair of data lines. The circuit comprises a fist equalizing element that is operatively coupled between the pair of data lines for equalizing the signal, the first equalizing element being located proximate a first end of the pair of data lines. The circuit further comprises a precharging element that is operatively coupled between the pair of data lines for precharging the pair of data lines to a precharge voltage, the precharging element being located proximate to the first equalizing element. The circuit also comprises a second equalizing element that is operatively coupled between the pair of data lines for equalizing the signal, and located at a predetermined position along the data lines. As a result of having multiple equalizing elements located along pairs of bit lines, the precharge and equalize function is performed faster than in conventional approaches.
Description
- This application is a Continuation Application from U.S. application Ser. No. 10/336,851 filed Jan. 6, 2003 which in turn is a Continuation Application from International Application No. PCT/CA00/01008, filed Aug. 31, 2000, which claims priority from Canadian Application Serial No. 2,313,951, filed Jul. 7, 2000 and U.S. Application No. 60/216,680, filed Jul. 7, 2000.
- The present invention relates generally to a system and method for improving bit line equalization in a semiconductor memory.
- Traditionally, designers of mass-produced or commodity dynamic random access memory (DRAM) devices have focused more on achieving a lower cost per bit through high aggregate bit density than on high memory performance. Typically, the low cost per bit has been achieved by designing DRAM architectures with sub-arrays as large as practically possible despite its strongly negative affect on the time required to perform bit line pre-charge and equalization, as well as cell read-out, sensing, and writing new values. The reason for the above designs is due to the fact that the cell capacity of a two dimensional memory array increases quadratically with scaling, while the overhead area of support circuitry increases linearly with scaling. The support circuitry includes bit line sense amplifiers, word line drivers, and X and Y address decoders. Thus, a relatively small increase in overhead area provides a relatively large increase in cell capacity.
- The bit line equalization and pre-charge portion of a DRAM row access cycle represents operational overhead that increases the average latency of memory operations and reduces the rate at which row accesses can be performed. Part of the difficulty in reducing this latency is due to typical DRAM architectures, which maximize memory capacity per unit area by favouring large DRAM cell arrays. Large DRAM cell arrays require long bit lines, which are highly capacitive. Thus, the bit lines require a relatively large amount of current to quickly change the voltage on them, as described in U.S. Pat. No. 5,623,446 issued Hisada et al.
- Hisada et al. describe a system for providing semiconductor memory with a booster circuit. The booster circuit boosts the voltage on the gates of the precharge and equalize devices during a selected portion of time in an attempt to decrease the precharge time. However, this approach requires higher power, which is undesirable for many applications.
- At the same time, the width of large DRAM arrays requires the simultaneous pre-charge and equalization of thousands of bit lines. The large number of active bit lines limits the drive strength of pre-charge and equalization devices for individual bit line pairs. This is in order to avoid difficulties associated with large peak aggregate currents.
- In contrast to commodity DRAM architectures, new DRAM architectures for embedded applications often focus on performance rather than the density. This is achieved by increasing the degree of subdivision of the overall memory into a large number of sub-arrays. Smaller active sub-arrays permit the use of higher drive, faster pre-charge and equalization circuits than possible in commodity memory devices. A memory of such architecture is illustrated in U.S. Pat. No. 6,023,437 issued to Lee.
- Lee describes a semiconductor device wherein the memory in segmented into components and adjacent memories share a sense amplifier. The semiconductor includes a blocking circuit for blocking bit lines associated with the memory component not in use. The semiconductor is capable of reducing the bit line precharge time, by improving the operation of the blocking circuits. However, this approach runs into fundamental limitations regarding how much the bit line equalization period can be shortened due to the distributed resistive and capacitive parasitic characteristics of the bit line material.
- Latency impact of slow bit line equalization and pre-charge has traditionally been minimized by the creation of two different classes of memory operations. A first class comprises bank accesses. Bank accesses require full row or column access in order to access a memory location. A second class comprises page accesses. Page accesses are typically faster than bank accesses and only require column access to a row that has been left open from a previous bank operation. The efficacy of page accesses in reducing average latency is due to the statistical spatial locality in the memory access patterns of many computing and communication applications. That is, there is a strong probability that consecutive memory accesses will target the same row.
- However, this architecture is undesirable for many applications such as real time control and digital signal processing that value deterministic, or at least minimum assured levels of memory performance regardless of the memory address access pattern. One solution is to perform a complete row and column access for every memory operation and automatically close the row at the end of the operation. Unfortunately, even the use of a highly subdivided, small sub-array DRAM architecture is performance limited by the distributed resistive-capacitive (RC) parasitic characteristics of the bit line material due to current DRAM design and layout practices.
- Therefore, it is an object of the present invention to provide an equalization circuit that obviates or mitigates one or more of the above mentioned disadvantages.
- An equalization circuit in accordance with the invention comprises a pair of data lines having a first end and a second end. A first equalizing element is operatively coupled between the pair of data lines. The first equalizing element is located proximate to the first end of the pair of data lines. A precharging element for precharging the pair of data lines to a precharge voltage level is operatively coupled between the pair of data lines and is positioned proximate to the first equalizing element. A second equalizing element is operatively coupled between the pair of data lines. The second equalizing element is positioned along the pair of data lines in spaced apart relation to the first equalizing element.
- Advantageously, the additional equalization element located along the data line allows faster precharge and equalization operations.
- Embodiments of the invention will now be described by way of example only with reference to the following drawings in which:
- FIG. 1a is a schematic diagram of memory array circuit (prior art);
- FIG. 1b is a schematic diagram of an alternate embodiment of the memory array circuit illustrated in FIG. 1a (prior art);
- FIG. 2a is a schematic diagram of a bit line pair illustrated in FIGS. 1a and 1 b (prior art);
- FIG. 2b is a schematic diagram of an equivalent model of the bit line pair illustrated in FIG. 2a (prior art)
- FIG. 3a is a schematic diagram of a memory array circuit in accordance with an embodiment of the present invention;
- FIG. 3b is a schematic diagram of an alternate embodiment of the memory array circuit illustrated in FIG. 3a;
- FIG. 4a is a schematic diagram of a bit line pair illustrated in FIGS. 3a and 3 b;
- FIG. 4b is a schematic diagram of equivalent model of the bit line pair illustrated in FIG. 4a;
- FIG. 5a is a schematic diagram of yet an alternate embodiment of the memory array circuit illustrated in FIG. 3a; and
- FIG. 5b is a schematic diagram of an alternate embodiment of the memory array circuit illustrated in FIG. 5a.
- Referring to FIG. 1a, a bit line precharge and equalization circuit illustrating a prior art DRAM architecture is illustrated generally by
numeral 100. Thecircuit 100 comprises amemory cell array 101, having memory cells located at the intersection of ones of a plurality bit line pairs 102 and word lines 108. Eachbit line pair 102 is comprised of a first ortrue bit line 102 a and a second line orcomplementary bit line 102 b. Asense amplifier 104 is operatively coupled between thetrue bit line 102 a and thecomplementary bit line 102 b at one end of thebit line pair 102. Aprecharge equalization circuit 106 is also operatively coupled between thetrue bit line 102 a and thecomplementary bit line 102 b at the same end of thebit line pair 102 as thesense amplifier 104. Memorycell access transistors 105 are located atword line 108 andbit line 102 intersections for accessing the memory cells. - As may be seen in FIG. 1a, the
sense amplifier 104 and theprecharge circuit 106 are arranged incircuit 100 to be located together on the same side of the memory cell array for each bit line pair. Alternately, thesense amplifier 104 and the precharge andequalization circuit 106 may be located together on opposite sides of the memory of cell array for adjacent bit line pairs, as shown in FIG. 12b. Furthermore, thesense amplifier 104 and the precharge andequalization circuit 106 may also be located separately on opposite sides of the memory cell array for each bit line pair (not shown). - As is well known, bit line precharge and equalization is performed by the
precharge circuit 106. The precharge andequalization circuit 106 comprises three n-channel transistors N1, N2, and N3. The drain and the source of transistor N1 are operatively coupled between thetrue bit line 102 a and thecomplementary bit line 102 b of thebit line pair 102. The gate of the equalization transistor N1 is operatively coupled to an equalization enableline 110. - The drain of transistor N2 is connected to the
true bit line 102 a of the bit line pair. The source of N2 is connected to both the drain of N3 and a bit lineprecharge voltage V blp 112. The source of N3 is operatively coupled with thecomplementary bit line 102 b of thebit line pair 102. The gates for both N2 and N3 are operatively coupled with theequalization line 110. - Transistor N1 equalizes the voltage on the associated true 102 a and complimentary 102 b bit lines, while transistors N2 and N3 drive the true 102 a and complimentary 102 b bit lines respectively to the precharge voltage level.
- During a DRAM read operation, the bit
line sense amplifiers 104 sense the voltage difference between the true 102 a and complimentary 102 b bit lines induced from a read out of an associated charge within an accessed memory cell. Thesense amplifier 104 amplifies the voltage difference until the bit line with the higher voltage is raised to approximately the positive supply voltage rail Vdd while the bit line with the lower voltage is pulled to approximately the ground supply voltage rail Vss. Typically, the bit lineprecharge voltage V blp 112 is set close to midway between Vdd and Vss. - Theoretically, only transistor N1 is needed for the precharge voltage because the precharged voltage can be achieved by charge sharing between the true 102 a and complimentary 102 b bit lines when the two are shorted together through N1. In practice, however, leakage, capacitive coupling, asymmetries in bit line capacitance, and other effects require some current to be supplied through transistors N2 and N3 for restoring the
bit line pair 102 to the bit lineprecharge voltage V blp 112. - Referring to FIG. 2(a), a circuit diagram of a
bit line pair 102 is shown generally by the numeral 200. Thecircuit 200 includes theprecharge circuit 106 as well as the memorycell access transistors 105. As previously described the precharge and equalization circuitry, that is transistors N1, N2, and N3, is located at one end of thebit line pair 102. The bit lines have significant distributed RC parasitic characteristics due to the small width of bit lines 102. The bit lines are typically placed as close together as possible in order to achieve a high memory density thus the width of the bit lines is at a minimum, or near minimum value. - Furthermore, the memory
cell access transistors 105 attached to the bit lines have an associated drain-capacitance that adds to the distributed RC parasitic characteristics. The RC parasitic characteristics cause an increase in the time required to equalize thebit line pair 102. Therefore, the time needed to equalize and precharge a bit line pair is approximately proportional to the square of the bit line's length within the memory array. - Referring to FIG. 2b, an equivalent model to the circuit illustrated in FIG. 2a is shown generally by the numeral 250. The
equivalent model 250 illustrates the resistive and capacitive elements in the memory cell array as resistors and capacitors equivalent to the resistance and capacitance presented by the actual circuit. - Referring to FIG. 3a, a circuit for reducing the time required for precharging a bit line pair according to an embodiment of the invention is illustrated generally by the numeral 300. The circuit includes a plurality of bit line pairs 102, word lines 108, memory
cell access transistors 105, and asense amplifier 104 and aprecharge circuit 106 located at one end of eachbit line pair 102. Thecircuit 300 further includes anadditional transistor N4 302 located at an end of the bit line pair opposite to thesense amplifier 104 and the precharge andequalization circuit 106. - The drain of transistor N4 is coupled to the true 102 a bit line and the source of N4 is coupled to the complimentary 102 b bit line. The gate of N4 is coupled to an equalization enable
line 110. The addition of transistor N4 effectively halves the length of the bit line as far as the RC delay is concerned and reduces the time needed to perform bit line equalization and precharge time. Typically the equalization and precharge time is reduced by approximately 75% as compared to prior art circuits. The location of transistor N4 is more important than the extra drive that it provides. - Thus, the addition of at least one extra equalization transistor along a bit line pair ensures that the distributed capacitance of the bit line pair and the associated memory cell transistors is more readily overcome with the additional drive provided by the extra equalization transistor(s). Particularly for embedded memory applications, additional area required to implement the extra equalization transistor(s) per bit line pair is readily compensated by the resulting decrease in precharge and equalization timing. This timing decrease, in turn, greatly decreases the overall delay between memory accesses, thereby providing an embedded memory implementation its main advantage over discrete commodity memory implementations.
- Referring to FIG. 3(b), an alternate embodiment of the above-described circuit is represented generally by the numeral 350. Similarly to FIG. 1(b), the
sense amplifier 104 and precharge andequalization circuit 106 for each bit line pair located together on opposite sides of the memory cell array for alternating bit line pairs. Therefore, the additional transistor N4 is also on opposite sides of the memory cell array for adjacent bit line pairs. - Referring to FIG. 4a, a bit line pair including memory
cell access transistors 105 is shown generally by the numeral 400. Referring then to FIG. 4b, an equivalent circuit to that of the physical circuit illustrated in FIG. 4(a) is shown generally by the numeral 450. Theequivalent circuit 450 provides a model illustrating the resistive and capacitive elements in the memory cell array as well as the fact that each transistor N1 and N4 is only responsible for equalizing and precharging half the length of the bit line pair. As a result, the delay associated with the precharge and equalize operation becomes proportional to one quarter (¼) the bit line length squared, i.e. delay ∝ (bit line length)2. - Referring to FIGS. 5a and 5 b, further alternate embodiments of bit line pair circuits are illustrated generally by the
numerals bit line pair 102 in half, thus allowing the size of transistor N1 to be reduced. Essentially, the equalizing effect of transistor N4 is felt on both sides of the bit line pair due to its central location. As a result, the equalization effect of transistor N1 is decreased compared to the case where transistor N4 is located at the opposite end of the bit line pair. That is, N1 can be decreased in size. - In addition to the configurations shown in FIGS. 5a and 5 b, the placement of the additional bit line equalization transistor N4 may also be staggered with each adjacent bit line pair due to the tight spacing within the middle of the array (not shown). By staggering it is meant that the equalization transistors N4 are placed to the left and right of the halfway point for adjacent bit line pairs. The sense amplifier and precharge and equalization transistors N1, N2 and N3 are preferably positioned on the same side as the position of the N4 device, but at the end of the array. This staggered configuration can be used such that the space between bit line pairs does not have to be increased. If the additional bit line equalization transistors N4 were placed directly below each other, the spacing requirements between bit line pairs would increase.
- In general, the invention can be applied to other situations where long pairs of data lines are used to transmit data either differentially or dual rail, and the signal pair is equalized between transmission of data items. Such systems include high performance SRAMs, other types of electronic memories that are arranged in arrays, and long, high fan-out data buses within the data paths of digital signal processors and microprocessors.
- Although n-channel transistors are used in the above description, it will be apparent to a person skilled in the art to use p-channel transistor. Furthermore, although the invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art without departing from the spirit and scope of the inventions as outlined in the claims appended hereto.
Claims (20)
1. An equalization circuit comprising:
a) a pair of data lines having a first end and a second end;
b) a first equalizing element operatively coupled between the pair of data lines, the first equalizing element located proximate to the first end;
c) a precharging element for precharging the pair of data lines to a precharge voltage level, the precharging element being operatively coupled between the pair of data lines and positioned proximate to the first equalizing element; and
d) a second equalizing element operatively coupled between the pair of data lines, the second equalizing element positioned along the pair of data lines in spaced apart relation to the first equalizing element.
2. An equalization circuit according to claim 1 , wherein the pair of data lines comprise a pair of bit lines in a memory cell array.
3. An equalization circuit according to claim 2 , further comprising:
a) a memory cell having a capacitor and an access transistor for coupling the capacitor to one bit line of the pair of bit lines; and
b) a sense amplifier coupled between the pair of bit lines, the sense amplifier for amplifying a voltage differential between the pair of bit lines.
4. An equalization circuit according to claim 2 , wherein the memory cell array includes a plurality of pairs of bit lines.
5. An equalization circuit according to claim 1 , wherein the first equalizing element comprises a first transistor coupled between the pair of data lines and being responsive to a first equalization signal and the second equalizing element comprises a second transistor coupled between the pair of data lines and being responsive to a second equalization signal.
6. An equalization circuit according to claim 5 , wherein the first and second transistors are n-channel transistors.
7. An equalization circuit according to claim 5 , wherein the first and second transistors are p-channel transistors.
8. An equalization circuit according to claim 5 , wherein the precharging element comprises a precharge transistor coupled to each of the pair of data lines, the precharge transistor for coupling a precharge voltage source to the data line.
9. An equalization circuit according to claim 8 , wherein the precharge transistor is an n-channel transistor.
10. An equalization circuit according to claim 8 , wherein the precharge transistor is a p-channel transistor.
11. An equalization circuit according to claim 1 , wherein the second equalizing element is positioned proximate to the second end of the pair of data lines.
12. An equalization circuit according to claim 1 , wherein the second equalizing element is positioned proximate to a halfway point between the first end and the second end of the pair of data lines.
13. An equalization circuit according to claim 1 , wherein the data lines are used to transmit data in a differential mode.
14. An equalization circuit according to claim 1 , wherein the data lines are used to transmit data in a dual rail mode.
15. A semiconductor memory cell array comprising:
a) a plurality of pairs of bit lines having a first end and a second end, each bit line having a plurality of memory cells coupled thereto;
b) a sense amplifier coupled between each bit line pair, the positioning of the sense amplifier in adjacent rows alternating between the first end and the second end;
c) a first equalizing element coupled between each pair of bit lines, the first equalizing element located proximate to the sense amplifier; and
d) a second equalizing element coupled between the pair of bit lines, the second equalizing element positioned along the pair of bit lines in spaced apart relation to the sense amplifier.
16. A semiconductor memory cell array according to claim 15 , wherein the memory cells are DRAM cells.
17. A semiconductor memory cell array according to claim 15 , further comprising a precharging element for precharging the pair of bit lines to a precharge voltage level, the precharging element operatively coupled between each pair of bit lines.
18. A semiconductor memory cell array according to claim 17 , wherein the precharging element comprises a precharge transistor coupled to each of the bit lines, the precharge transistor for coupling a precharge voltage to the bit line.
19. A semiconductor memory cell array according to claim 17 , wherein for each pair of bit lines the precharging element is positioned proximate to the sense amplifier.
20. A semiconductor memory cell array according to claim 15 , wherein the first and second equalizing elements comprise a transistor coupled between the pairs of bit lines.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/855,410 US20040264272A1 (en) | 2000-07-07 | 2004-05-28 | Method and apparatus for accelerating signal equalization between a pair of signal lines |
Applications Claiming Priority (6)
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---|---|---|---|
US21668000P | 2000-07-07 | 2000-07-07 | |
CA 2313951 CA2313951A1 (en) | 2000-07-07 | 2000-07-07 | Scheme for accelerating bit line equalization in a high speed dram architecture |
CA2,313,951 | 2000-07-07 | ||
PCT/CA2000/001008 WO2002005289A1 (en) | 2000-07-07 | 2000-08-31 | A method and apparatus for accelerating signal equalization between a pair of signal lines |
US10/336,851 US6785176B2 (en) | 2000-07-07 | 2003-01-06 | Method and apparatus for accelerating signal equalization between a pair of signal lines |
US10/855,410 US20040264272A1 (en) | 2000-07-07 | 2004-05-28 | Method and apparatus for accelerating signal equalization between a pair of signal lines |
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US10/336,851 Continuation US6785176B2 (en) | 2000-07-07 | 2003-01-06 | Method and apparatus for accelerating signal equalization between a pair of signal lines |
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US20040264272A1 true US20040264272A1 (en) | 2004-12-30 |
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Family Applications (2)
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US10/336,851 Expired - Fee Related US6785176B2 (en) | 2000-07-07 | 2003-01-06 | Method and apparatus for accelerating signal equalization between a pair of signal lines |
US10/855,410 Abandoned US20040264272A1 (en) | 2000-07-07 | 2004-05-28 | Method and apparatus for accelerating signal equalization between a pair of signal lines |
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US10/336,851 Expired - Fee Related US6785176B2 (en) | 2000-07-07 | 2003-01-06 | Method and apparatus for accelerating signal equalization between a pair of signal lines |
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US (2) | US6785176B2 (en) |
KR (1) | KR20030037263A (en) |
CN (1) | CN1454385A (en) |
AU (1) | AU2000268134A1 (en) |
DE (1) | DE10085476T1 (en) |
GB (1) | GB2379546A (en) |
WO (1) | WO2002005289A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20050265095A1 (en) * | 2004-05-31 | 2005-12-01 | Matsushita Electric Industrial Co., Ltd. | Semiconductor integrated circuit |
US20060023529A1 (en) * | 2004-07-16 | 2006-02-02 | Faue Jon A | Dual equalization devices for long data line pairs |
US9064555B2 (en) | 2012-11-26 | 2015-06-23 | Oracle International Corporation | Secondary bit line equalizer |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6928012B2 (en) * | 2002-09-27 | 2005-08-09 | Infineon Technologies Ag | Bitline equalization system for a DRAM integrated circuit |
US7443747B2 (en) * | 2004-08-09 | 2008-10-28 | Integrated Device Technology, Inc. | Memory array bit line coupling capacitor cancellation |
KR100772700B1 (en) * | 2006-06-29 | 2007-11-02 | 주식회사 하이닉스반도체 | Memory device that have bitline equalizing unit in cell array, and method for locating bitline equalizing unit in cell array |
KR100761854B1 (en) * | 2006-08-08 | 2007-09-28 | 삼성전자주식회사 | Bit-line equalizer and semiconductor memory device comprising it, and method for manufacturing the bit-line equalizer |
US7800965B2 (en) * | 2008-03-10 | 2010-09-21 | Micron Technology, Inc. | Digit line equilibration using access devices at the edge of sub-arrays |
US10632756B2 (en) | 2016-07-19 | 2020-04-28 | Hewlett-Packard Development Company, L.P. | Fluid level sensors |
Citations (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5233558A (en) * | 1990-12-14 | 1993-08-03 | Kabushiki Kaisha Toshiba | Semiconductor memory device capable of directly reading the potential of bit lines |
US5247482A (en) * | 1991-05-24 | 1993-09-21 | Samsung Electronics Co., Ltd. | Semiconductor memory device with high speed write operation |
US5291433A (en) * | 1991-09-13 | 1994-03-01 | Oki Electric Industry Co., Ltd. | Semiconductor memory with leak-resistant bit lines |
US5349560A (en) * | 1992-03-30 | 1994-09-20 | Samsung Electronics Co., Ltd. | Semiconductor memory device with improved bit line precharged circuits |
US5487044A (en) * | 1992-03-19 | 1996-01-23 | Kabushiki Kaisha Toshiba | Semiconductor memory device having bit line equalizing means |
US5623446A (en) * | 1993-08-12 | 1997-04-22 | Kabushiki Kaisha Toshiba | Semiconductor integrated circuit having a voltage booster and precharging circuit |
US5673219A (en) * | 1996-03-21 | 1997-09-30 | Texas Instruments Incorporated | Apparatus and method for reducing leakage current in a dynamic random access memory |
US5717645A (en) * | 1997-02-07 | 1998-02-10 | Alliance Semiconductor Corporation | Random access memory with fast, compact sensing and selection architecture |
US5757707A (en) * | 1994-05-31 | 1998-05-26 | Kabushiki Kaisha Toshiba | Semiconductor memory device |
US6023437A (en) * | 1997-11-20 | 2000-02-08 | Samsung Electronics Co., Ltd. | Semiconductor memory device capable of reducing a precharge time |
US6166976A (en) * | 1998-06-03 | 2000-12-26 | G-Link Technology | Multiple equilibration circuits for a single bit line |
US6278650B1 (en) * | 1999-10-27 | 2001-08-21 | Samsung Electronics Co., Ltd. | Semiconductor memory device capable of keeping sensing efficiency of data line sense amplifier uniform |
US6307768B1 (en) * | 2000-12-28 | 2001-10-23 | Infineon Technologies Richmond, Lp | Bitline twist with equalizer function |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5823446A (en) * | 1997-02-18 | 1998-10-20 | Awalbro Corporation | Fuel injector valve for liquified fuel |
-
2000
- 2000-08-31 KR KR10-2003-7000243A patent/KR20030037263A/en not_active Application Discontinuation
- 2000-08-31 WO PCT/CA2000/001008 patent/WO2002005289A1/en active Search and Examination
- 2000-08-31 GB GB0230353A patent/GB2379546A/en not_active Withdrawn
- 2000-08-31 AU AU2000268134A patent/AU2000268134A1/en not_active Abandoned
- 2000-08-31 CN CN00819733A patent/CN1454385A/en active Pending
- 2000-08-31 DE DE10085476T patent/DE10085476T1/en not_active Withdrawn
-
2003
- 2003-01-06 US US10/336,851 patent/US6785176B2/en not_active Expired - Fee Related
-
2004
- 2004-05-28 US US10/855,410 patent/US20040264272A1/en not_active Abandoned
Patent Citations (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5233558A (en) * | 1990-12-14 | 1993-08-03 | Kabushiki Kaisha Toshiba | Semiconductor memory device capable of directly reading the potential of bit lines |
US5247482A (en) * | 1991-05-24 | 1993-09-21 | Samsung Electronics Co., Ltd. | Semiconductor memory device with high speed write operation |
US5291433A (en) * | 1991-09-13 | 1994-03-01 | Oki Electric Industry Co., Ltd. | Semiconductor memory with leak-resistant bit lines |
US5487044A (en) * | 1992-03-19 | 1996-01-23 | Kabushiki Kaisha Toshiba | Semiconductor memory device having bit line equalizing means |
US5349560A (en) * | 1992-03-30 | 1994-09-20 | Samsung Electronics Co., Ltd. | Semiconductor memory device with improved bit line precharged circuits |
US5623446A (en) * | 1993-08-12 | 1997-04-22 | Kabushiki Kaisha Toshiba | Semiconductor integrated circuit having a voltage booster and precharging circuit |
US5757707A (en) * | 1994-05-31 | 1998-05-26 | Kabushiki Kaisha Toshiba | Semiconductor memory device |
US5673219A (en) * | 1996-03-21 | 1997-09-30 | Texas Instruments Incorporated | Apparatus and method for reducing leakage current in a dynamic random access memory |
US5717645A (en) * | 1997-02-07 | 1998-02-10 | Alliance Semiconductor Corporation | Random access memory with fast, compact sensing and selection architecture |
US6023437A (en) * | 1997-11-20 | 2000-02-08 | Samsung Electronics Co., Ltd. | Semiconductor memory device capable of reducing a precharge time |
US6166976A (en) * | 1998-06-03 | 2000-12-26 | G-Link Technology | Multiple equilibration circuits for a single bit line |
US6278650B1 (en) * | 1999-10-27 | 2001-08-21 | Samsung Electronics Co., Ltd. | Semiconductor memory device capable of keeping sensing efficiency of data line sense amplifier uniform |
US6307768B1 (en) * | 2000-12-28 | 2001-10-23 | Infineon Technologies Richmond, Lp | Bitline twist with equalizer function |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20050265095A1 (en) * | 2004-05-31 | 2005-12-01 | Matsushita Electric Industrial Co., Ltd. | Semiconductor integrated circuit |
US7161859B2 (en) * | 2004-05-31 | 2007-01-09 | Matsushita Electric Industrial Co., Ltd. | Semiconductor integrated circuit |
US20060023529A1 (en) * | 2004-07-16 | 2006-02-02 | Faue Jon A | Dual equalization devices for long data line pairs |
US7218564B2 (en) * | 2004-07-16 | 2007-05-15 | Promos Technologies Inc. | Dual equalization devices for long data line pairs |
US9064555B2 (en) | 2012-11-26 | 2015-06-23 | Oracle International Corporation | Secondary bit line equalizer |
Also Published As
Publication number | Publication date |
---|---|
US6785176B2 (en) | 2004-08-31 |
CN1454385A (en) | 2003-11-05 |
GB0230353D0 (en) | 2003-02-05 |
WO2002005289A1 (en) | 2002-01-17 |
AU2000268134A1 (en) | 2002-01-21 |
KR20030037263A (en) | 2003-05-12 |
US20030142567A1 (en) | 2003-07-31 |
DE10085476T1 (en) | 2003-12-11 |
GB2379546A (en) | 2003-03-12 |
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