Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Amplitude control
Reexamination Certificate
2001-03-13
2002-12-31
Cunningham, Terry D. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Amplitude control
C327S313000, C327S314000, C327S318000
Reexamination Certificate
active
06501319
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to semiconductor devices, and more particularly to a semiconductor device with a signal transfer line.
2. Description of the Background Art
FIG. 11
is a block diagram showing a main part of a conventional semiconductor integrated circuit device.
Referring to
FIG. 11
, the semiconductor integrated circuit device includes a bus
30
, a transmission side circuit
31
connected to one end of bus
30
, and a reception side circuit
32
connected to the other end of bus
30
. Bus
30
includes N (N is an integer of at least 2) bus lines L
1
-LN.
Signals VO
1
-VON output from transmission side circuit
31
are transferred to reception side circuit
32
via bus lines L
1
-LN, respectively. Reception side circuit
32
responds to signals VO
1
-VON to carry out a predetermined operation.
FIG. 12
shows the semiconductor integrated circuit device of
FIG. 11
in more detail. In
FIG. 12
, only the four adjacent bus lines Ln−1~Ln+2 out of the N bus lines L
1
-LN and components corresponding thereto are depicted.
Referring to
FIG. 12
, four drivers
33
are provided corresponding to four bus lines Ln−1~Ln+2, respectively, at reception side circuit
31
. The four drivers
33
are rendered active in response to a driver control signal/E attaining an activation level of “L” to provide signals VOn−1~VOn+2 having levels identical to those of internal signals VIn−1~VIn+2 to one ends of bus lines Ln−1~Ln+2.
Each of bus lines Ln−1~Ln+2 has a line resistance R and a inter-line capacitance C of values determined by the line length, line width, and the like. Signals VOn−1~VOn+2 applied to one ends of bus lines Ln−1~Ln+2 are transmitted to the other ends of bus lines Ln−1~Ln+2.
Four receivers
34
are provided corresponding to four bus lines Ln−1~Ln+2 at reception side circuit
32
. The four receivers
34
detect whether the potentials at the other ends of bus lines Ln−1~Ln+2 are higher or lower than the reference potential, and reproduces signals VIn−1~VIn+2 according to the detected result. Reception side circuit
32
carries out a predetermined operation according to the reproduced signals VIn−1~VIn+2.
In such a semiconductor integrated circuit device, the occupation ratio of inter-line capacitance C as to the capacitance of the wiring is increasing according to the microminiaturization of the process. For example, in the 0.15 &mgr;m process, inter-line capacitance C corresponds to 90% of the capacitance of the wiling, whereas the remaining 10% corresponds to the line-substrate capacitance, fringe capacitance, and the like. In a semiconductor integrated circuit device, coupling noise by interline capacitance C has become problematic.
For example, when signal VIn is driven from an L level to an H level or from an H level to an L level under the state where signal VIn+1 is held at an H level or an L level in
FIG. 12
, the level of signal VOn+1 will be altered by the coupling noise.
More specifically, in the case where signal VIn is driven from an L level to an H level when signal VOn+1 is at an H level as shown in
FIG. 13
, signal VOn+1 rises in a pulsive manner (this noise is referred to as “coupling noise
1
” hereinafter). In the case where signal VIn is driven to an L level from an H level when signal VOn+1 is at an L level, signal VOn+1 is reduced in a pulsive manner (this noise is referred to as “coupling noise
2
”).
In the case where signal VIn is pulled down to an L level from an H level when signal VOn+1 is at an H level, signal VOn+1 is reduced in a pulsive manner (this noise is referred to as “coupling noise
3
” hereinafter). In the case where signal VIn is pulled up to an H level from an L level when signal VOn+1 is at an L level, signal VOn+1 rises in a pulsive manner (this noise is referred to as “coupling noise
4
” hereinafter).
Coupling noises
1
and
2
among the above-described noises will delay the level change of signal VOn+1 when signal VOn+1 is altered in opposite phase to signal VOn, whereby the operating speed of the semiconductor integrated circuit is reduced. Also, coupling noises
3
and
4
cause receiver
34
to operate erroneously when signal VOn+1 attains a large noise that exceeds the reference potential of receiver
34
.
These problems have been dealt by setting the line intervals of bus lines L
1
-LN as wide as possible. However, bus lines L
1
-LN cannot enjoy the advantages of process microminiaturization with this measure. In microprocessors, memories, and the like, the amount of data to be processed at one time is increasing from 32 bits to 64 bits, and further to 128 bits corresponding to the requirement of high speed processing. As a result, the number N of bus lines L
1
-LN is also increasing. Therefore, increasing the interval of bus lines L
1
-LN is not preferable since the layout area will be increased.
SUMMARY OF THE INVENTION
In view of the foregoing, a main object of the present invention is to provide a semiconductor device of small layout area and low noise level.
According to an aspect of the present invention, a semiconductor device includes a driver having an output node connected to one end of a signal transfer line, driving the output node to a first potential in response to a first signal and to a second potential differing from the first potential in response to a second signal, and a noise limiter with a first diode element having a first electrode receiving a third potential corresponding to the first potential shifted in level towards the second potential side by a threshold voltage, and a second electrode connected to the signal transfer line, and rendered conductive in response to the potential of the signal transfer line exceeding the first potential. When coupling noise
1
or
2
is generated at the signal transfer line so that the potential of the signal transfer line exceeds the first potential, the first diode is rendered conductive to restore the potential of the signal transfer line to the first potential. Therefore, the level of coupling noise
1
or
2
can be reduced. Also, only a small layout area is required since the interval of the signal transfer lines does not have to be increased.
Preferably, the noise limiter includes a second diode element having a first electrode receiving a fourth potential corresponding to the second potential shifted in level towards the first potential side by a threshold voltage, and a second electrode connected to the signal transfer line, rendered conductive in response to the potential of the signal transfer line exceeding the second potential. When coupling noise
2
or
1
is generated at the signal transfer line so that the potential of the signal transfer line exceeds the second potential, the second diode element is rendered conductive to restore the potential of the signal transfer line to the second potential. Therefore, coupling noise
2
or
1
can be reduced.
The semiconductor device preferably includes a receiver having an input node connected to the other end of the signal transfer line to receive first and second signals by detecting the potential of the input node. The noise limiter is connected to the signal transfer line at a connection node closer to the input node of the receiver than the output node of the driver. Since coupling noises
1
and
2
become larger as approaching the receiver, coupling noises
1
and
2
can be reduced effectively by connecting the noise limiter with the signal transmission line at an output point closer to the input node of the receiver than the output node of the driver.
The noise limiter is preferably provided in the proximity of the input node of the receiver. Since coupling noises
1
and
2
attain the maximum level in the proximity of the receiver, coupling noises
1
and
2
can be reduced effectively by providing the noise limiter in the proxi
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