Electronic device

Details Electronic device Electronic device

1999-03-29

2003-02-18

Tokar, Michael (Department: 2819)

Electronic digital logic circuitry

Significant integrated structure, layout, or layout...

C326S047000, C326S086000, C333S001000, C333S012000, C333S025000, C333S238000, C710S120000

Reexamination Certificate

active

06522173

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic device having a transfer circuit which transfers a digital transmit signal output from a driver to a receiver via signal lines.
2. Description of the Related Art
FIG. 1
is a circuit diagram of an example of a conventional electronic device. The electronic device includes a CMOS differential driver
3
and a CMOS differential receiver
4
. The CMOS driver
3
converts a digital transmit signal into complementary transmission digital signals CS and /CS, which are output to signal lines
1
and
2
, respectively. The CMOS differential receiver
4
receives the complementary digital transmit signals CS and /CS transferred over the digital signal RS corresponding to the digital transmit signal TS.
The CMOS differential driver
3
includes a CMOS driver
5
, which outputs the positive phase digital transmit signal CS which is in phase with the digital transmit signal TS. The CMOS driver
5
includes an n-channel MOS (nMOS) transistor
6
serving as a pull-up element, and a p-channel MOS (pMOS) transistor
7
serving as a pull-down element. The CMOS differential driver
3
includes a CMOS inverter
8
, which includes a pMOS transistor
9
serving as a pull-up element, and an nMOS transistor
10
serving as a pull-down element.
The CMOS differential receiver
4
includes a CMOS driver
11
, which receives the in-phase phase digital transmit signal CS transferred over the signal line
1
. The CMOS driver
11
includes an nMOS transistor
12
serving as a pull-up element, and a pMOS transistor
13
serving as a pull-down element. The CMOS differential receiver
4
includes a CMOS inverter
14
, which receives the anti-phase digital transmit signal /CS transferred over the signal line
2
. The CMOS inverter
14
includes a pMOS transistor
15
serving as a pull-up element, and an nMOS transistor
16
serving as a pull-down element.
In the electronic device thus configured, when the digital transmit signal TS switches from the low level to the high level, the nMOS transistor
6
of the CMOS driver
5
is turned ON, and the pMOS transistor
7
is turned OFF. Further, the pMOS transistor
9
of the CMOS inverter
8
is turned OFF and the nMOS transistor
10
thereof is turned ON.
Hence, a charge which switches the input terminal of the CMOS driver
11
to the high level from the low level is supplied to the signal line
1
via the CMOS driver
5
, and a charge which switches the input terminal of the CMOS inverter
14
to the low level from the high level is drawn to the ground from the signal line
2
via the CMOS inverter
8
.
The above phenomenon can be understood so that positive signal energy which changes the input terminal of the CMOS driver
11
from the low level to the high level is supplied to the signal line
1
from the CMOS drier
5
and negative signal energy which changes the input terminal of the CMOS inverter
14
from the high level to the low level is supplied to the signal line
2
from the CMOS inverter
8
.
When the input terminal of the CMOS driver
11
switches from the low level to the high level and the input terminal of the CMOS inverter
14
switches from the high level to the low level, the nMOS transistor
12
of the CMOS driver
11
is turned ON and the pMOS transistor
13
is turned OFF. Further, the pMOS transistor
15
of the CMOS inverter
14
is turned ON, and the nMOS transistor
16
thereof is turned OFF.
Hence, the outputs of the CMOS driver
11
and the CMOS inverter
14
are turned to the high level from the low level. Thus, the receive digital signal RS output by the CMOS differential receiver
4
is switched to the high level from the low level. Thus, the CMOS differential receiver
4
substantially receives the digital transmit signal TS.
In contrast, when the digital transmit signal TS switches from the high level to the low level, the nMOS transistor
6
of the CMOS driver
5
is turned OFF, and the pMOS transistor
7
is turned ON. Further, the pMOS transistor
9
of the CMOS inverter
8
is turned ON, and the nMOS transistor
10
thereof is turned OFF.
Hence, a charge which switches the input terminal of the CMOS driver
11
from the high level to the low level is drawn to the ground from the signal line
1
via the CMOS driver
5
, and a charge which switches the input terminal of the CMOS inverter
14
from the low level to the high level is supplied to the signal line
2
from the CMOS inverter
8
.
The above phenomenon can be considered so that negative signal energy which changes the input terminal of the CMOS driver
11
from the high level to the low level is supplied to the signal line
1
from the CMOS driver
5
, and positive signal energy which changes the input terminal of the CMOS inverter
14
from the low level to the high level is supplied to the signal line
2
from the CMOS inverter
8
.
When the input terminal of the CMOS inverter
11
switches from the high level to the low level and the input terminal of the CMOS inverter
14
switches from the low level to the high level, the nMOS transistor
12
of the CMOS driver
11
is turned OFF and the pMOS transistor
13
thereof is turned ON. Further, the pMOS transistor
15
of the CMOS inverter
14
is turned OFF and the nMOS transistor
16
thereof is turned ON.
Hence, the outputs of the CMOS driver
11
and the CMOS inverter
14
are switched from the high level to the low level. Hence, the receive digital signal RS output by the CMOS differential receiver
4
is switched from the high level to the low level. Thus, the CMOS differential receiver
4
substantially receives the digital transmit signal TS.
As described above, in the conventional electronic device shown in
FIG. 1
, complementary signal energy is supplied to the signal lines
1
and
2
from the CMOS differential driver
3
when the digital transmit signal TS changes, so that the complementary digital transmit signals CS and /CS derived from the digital transmit signal TS are transferred to the CMOS differential receiver
4
via the signal lines
1
and
2
.
When the signal lines
1
and
2
are equal-length parallel lines so that the coupling coefficient is close to 1, the signal lines
1
and
2
form a transfer path in which the electromagnetic field is approximately closed. Hence, the complementary digital transmit signals CS and /CS are transferred in a mode close to a TEM (Transversed Electromagnetic Mode), and thus speeding up of signal transfer can be achieved.
However it is to be noted that, when the complementary digital transmit signals CS and /CS are transferred to the CMOS differential receiver
4
from the CMOS differential driver
3
, complementary signal energy supplied to the signal lines
1
and
2
from the CMOS differential driver
3
are supplied from the power supply line. Hence, in order to further speed up the signal transfer, it is required to supply the complementary signal energy to the CMOS differential driver
3
from the power supply line at a higher speed. However, in this regard, there is no proposal.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an electronic device or apparatus equipped with a CPU and a plurality of memories in which a signal can be transferred between the CPU and the memories at a higher speed.
The above object of the present invention is achieved by an electronic device comprising: a wiring board; at least one pair of signal lines that are provided on the wiring board in parallel and have equal lengths; a chip that is mounted on the wiring board and includes at least one differential driver which outputs complementary digital transmit signals to the above-mentioned at lest one of the pair of lines; and a pair of power system lines through which first and second power supply voltages are supplied to the above-mentioned at least one differential driver, said pair of power system lines being parallel to each other and having an equal length.
When a transmit digital signal applied to the differential driver changes its level, resulta

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