JP2001111408A - Structure for packaging high speed signal transmission wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide high speed signal transmission wire packaging structure capable of reducing jitters by suppressing the timewise oscillation of a signal caused by a reflected wave reciprocally transmitted through a transmission wire for connecting a transmitting side semiconductor device to a receiving side semiconductor device especially in a signal transmission system consisting of the transmitting side and the receiving side. SOLUTION: A distance from a node between an output circuit of a semiconductor device 15a to be an impedance mismatched position of a transmitting substrate 100 and an output wire 16a to a node 26 to be an impedance mismatched position of a receiving substrate 200 is determined so that signal transmission time becomes integer times a half of a signal switching period. Consequently the influence of jitters due to a signal reflected by each of impedance mismatched positions of both the substrates 100, 200, is restrained so that the high speed signal transmission wire packaging structure capable of resisting signal transmission of a short signal switching period can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal transmission wiring mounting structure having a semiconductor element for signal processing on each of a transmission side and a reception side, and more particularly, to a high-speed circuit having impedance mismatching portions on each of a transmission side and a reception side. The present invention relates to a signal transmission wiring mounting structure.

[0002]

2. Description of the Related Art In a high-speed signal transmission wiring structure, a signal transmission circuit, a reception signal transmission circuit, a transmission signal transmission circuit, a reception signal transmission circuit, and a transmission signal transmission circuit are usually used in order to suppress signal reflection and match the transmission circuit and the reception circuit. A method of equalizing the characteristic impedance of the wiring has been adopted. Regarding the signal transmission wiring structure, for example,
As described in JP-A-27697, a signal transmission circuit for a picture tube provided with a broadband drive circuit, the output impedance of a voltage amplification transistor on a drive circuit board, the impedance of a transmission line, and the receiving end on a picture tube substrate A transmission wiring structure having the same impedance has been reported.

[0003]

An electronic device such as a computer is required to operate at a high speed. A signal processing circuit capable of performing a high-speed and large-scale processing, and an interface for transmitting a processed signal at a high speed. In addition, a signal transmission wiring structure is required. In particular, if there is a reflected wave in high-speed signal transmission, the reflected wave is superimposed on the original transmission signal, causing waveform distortion, and the temporal fluctuation of the signal called jitter increases. Since this jitter causes a malfunction of the electronic device, it is necessary to minimize the jitter. Therefore, it is necessary to design a signal transmission wiring mounting structure that reduces the influence of the reflected wave.

When a transmitted signal is transmitted to a receiving substrate in a signal transmission system, a delay occurs in a signal propagated in proportion to the length of a transmission line. In a circuit in which the characteristic impedances of the transmission systems are all equal and are matched, signals can be transmitted without causing waveform disturbance. JP 5
Japanese Unexamined Patent Publication (Kokai) No. -27697 discloses that by configuring the ideal signal transmission system, a signal reflected wave can be suppressed. However, for example, in a high-speed signal transmission system using a CMOS transistor, it is difficult to match the output impedance of the CMOS transistor with the characteristic impedance of other elements constituting the transmission system such as a substrate wiring and a cable. For this reason, impedance mismatch occurs at the output stage of the CMOS transistor, and it is not possible to completely suppress the signal reflected wave. Further, the input circuit of the semiconductor device on the receiving side becomes a capacitive load, and the received signal is totally reflected.
Even if a termination resistor is attached near the input circuit of the semiconductor device,
Due to this capacitive load, signal reflection cannot be completely prevented.

An object of the present invention is to provide a high-speed signal transmission wiring mounting structure in which each of the signal wiring boards on the transmission side and the reception side has an impedance mismatching portion and both signal wiring boards are connected by transmission lines. To reduce the effect of reflected waves due to the presence of matching points, especially reflected waves that reciprocate on the transmission line connecting the transmission side and reception side signal wiring boards, the transmission line connecting the transmission side and reception side signal wiring boards An object of the present invention is to provide a high-speed signal transmission wiring mounting structure capable of defining a structure and a length and reducing jitter.

[0006]

In order to achieve the above object, a first semiconductor device having an output circuit is mounted, and an output wiring connected to the output circuit and a sending end means connected to the output wiring are provided. And a second substrate on which a second semiconductor device having an input circuit is mounted, and an input wiring connected to the input circuit and a terminating means connected to the input wiring are provided. A receiving board, comprising a cable connecting the output wiring and the input wiring, wherein an output impedance of the output circuit is different from a characteristic impedance of the output wiring, the cable and the input wiring, and a high-speed signal transmission wiring mounting structure; The sending end means is matched to the reflected wave and propagates between a connection point between the output circuit and the output wiring and a connection point between the input wiring and the termination means. Round-trip transmission time of the signal is obtained by an integral multiple of the switching period of the signal.

In order to achieve the above object, the transmitting end resistance is mismatched with respect to a reflected wave, and a connection point between the transmitting end means and the output wiring, and a connection point between the input wiring and the terminating means are provided. The round trip transmission time of the signal propagating between the connection points is
This is an integral multiple of the signal switching period.

The round-trip transmission time of a signal propagating between the point of maximum impedance mismatch with respect to the reflected wave of the transmitting board and the maximum point of impedance mismatch with respect to the traveling wave of the receiving board is the signal round-trip time. Is an integral multiple of the switching period.

[0009] Also, of the connection points of the output circuit, the transmitting end means and the wiring, a round-trip transmission of a signal propagating between the maximum point of impedance mismatch with respect to the reflected wave and the connection point of the wiring and the terminating resistor. The time is an integer multiple of the signal switching period.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a high-speed signal transmission wiring mounting structure according to the present invention will be described below with reference to FIGS.
First, the circuit and structure of the present embodiment will be described with reference to the circuit diagram of FIG. 1 and the structural perspective view of FIG. 2, respectively.

A first semiconductor device 15a provided with an output circuit 21 is mounted on a first substrate 11a, and is connected to a sending terminal circuit 24 via an output wiring 16a disposed on the first substrate 11a. Further, the transmission board 1 is connected to the output wiring 16a.
00. The second substrate 11 constituting the receiving substrate 200 via the cable 300 to the output wiring 16a
b, and is connected to the receiving wiring 16b. Further, the terminating means 25 is connected to the receiving wiring 16b,
Via the input circuit 23 provided in the second semiconductor device 15b
Connect to

As shown in FIG. 1, the output circuit 21 to the sending end means 24 and the terminating means 25 are constituted by using a resistor 18. The sending end circuit 24 includes a resistor 18 connected in series with the output wiring 16a.
And the output wiring 16a on the cable 300 side.
A resistor 18 is arranged at a reference potential from a connection point with the resistor 18. on the other hand,
The terminating means 25 is configured to connect the input wiring 16b and the reference potential by the resistor 18.

As shown in the mounting perspective view of FIG. 2, first and second semiconductor devices 15a and 15b
Was mounted on the semiconductor packages 14a and 14b. Also,
Although the transmission board 100, the cable 300, and the reception board 200 are connected using the connector 17, this is not an essential configuration.

Next, the operation of this embodiment will be described. The digital signal transmitted from the output circuit 21 is output from the output wiring 16.
a, the transmission end means 24, the output wiring 16a, the connector 17, the cable 300, the input wiring 16b, the terminating means 25, and the input wiring 16b are transmitted to the input circuit 23. During this time,
Although a part of the signal is reflected by the portions having different impedances of the respective portions, the amplitude of the reflected wave increases as the difference in impedance between the portions before and after the connection point increases. In particular, since the two are connected in parallel at the connection point 26 between the terminating means 25 and the input wiring 16b and the impedance is greatly reduced, a large reflected wave returns to the transmission board 100.

The reflected wave returns to the output circuit 21 through the reverse route. During this time, the sending end means is aligned with the reflected wave,
No further reflections occur here. The reflected wave reaching the output circuit 21 has an output impedance of the output circuit 21 different from that of the output wiring 16a. Therefore, the light is further reflected at these connection points. The reciprocating reflected wave is superimposed on the digital signal transmitted at the same time and reaches the input circuit 23, causing a voltage fluctuation to generate an undesirable jitter.

When a digital signal of 1 ns is input to the high-speed signal transmission wiring mounting structure of this embodiment, the switching period, that is, the minimum time of 0 or 1 when the signal is switched from 1 to 0 or from 0 to 1 , The length of the cable 300 to 100
FIG. 3 shows an example of the result of analyzing the jitter amount while changing the range from cm to 114 cm.

It has been found that the jitter periodically changes with a period of 13 cm in length. The cycle of the reciprocating length of 26 cm corresponds to the distance over which the signal propagates during a time of 1 ns in this embodiment. The length of the cable 13 that minimizes jitter is 106cm
, The signal transmission delay time of the reciprocating path between the output circuit 21 and the receiving-side wiring branch 26 is calculated as 1 Gbit / s
This is an integral multiple of the digital signal switching period of 1 ns. That is, the jitter can be minimized by determining the distance between the output circuit 21 and the receiving-side wiring branch 26 so that the signal transmission time is half the signal switching period and an integral multiple of 500 ps. I understood.

In this embodiment, there is shown a case where the number of the transmission board and the number of the reception board are one, and the output circuit and the input circuit are also one in the semiconductor device. However, the present invention is not limited to this. It goes without saying that the present invention is applicable to a wiring mounting structure that has a signal wiring board, is connected by transmission wiring and a cable, and transmits high-speed signals.

Next, another embodiment of the present invention will be described with reference to the circuit diagram of FIG. This circuit diagram differs from the circuit diagram of FIG. 1 only in the configuration of the sending end means 24, and therefore, duplicate description will be omitted.

In the transmitting means 24 of this embodiment, the arrangement of the resistors is changed to match the signal wave transmitted from the output circuit 21 to the input circuit 23, and the signal wave is mismatched with respect to the reflected wave. Are different. A part of the signal transmitted from the output circuit 21 is reflected at the connection point 26 between the terminating means 25 and the input wiring 16b as in the previous embodiment, and transmitted toward the transmitting end means 24. Since the transmitting end unit 24 is not matched with the reflected wave, the transmitted reflected wave is further reflected by the transmitting end unit 24 and transmitted toward the input circuit 23. This reciprocating reflected wave is superimposed on the digital signal transmitted at the same time and reaches the input circuit 23, which causes a voltage fluctuation and generates undesirable jitter.

In this embodiment, the connection point between the output wiring 16a on the cable 300 side and the sending end means 24 and the receiving wiring branch 26 are the main reflection points. That is, the transmission side wiring branch 4
Jitter can be minimized by setting the distance between 1 and the receiving-side wiring branch 26 such that the signal transmission time is an integral multiple of half the signal switching period. In this embodiment, there is one transmission board and one reception board. In addition, although one output circuit and one input circuit are shown in the semiconductor device, the present invention is not limited to this case. The semiconductor device has a plurality of signal wiring boards, is connected by transmission wiring and cables, and transmits high-speed signals. It is needless to say that the present invention can be applied to a wiring mounting structure.

The two embodiments have in common that the point of maximum impedance mismatch for the reflected wave of the transmitting board 100 and the point of maximum impedance mismatch for the traveling wave of the receiving board 200. Jitter can be reduced by setting the distance between them to be an integral multiple of the signal switching period for the round trip transmission time of the signal propagating between them.

Next, a circuit diagram of another embodiment of the present invention is shown in FIG. Since the configuration and effects are almost the same as those of the embodiment described with reference to FIG. 1, the description of the same parts as in FIG. 1 will be omitted. The semiconductor devices 15a and 15b on which the output circuit 21 and the input circuit 23 are mounted, the transmission wiring 16, the transmitting end means 24, and the terminating means 25 are mounted on the same mounting substrate 71, and the cable is eliminated. The arrangement is the same as that of the circuit diagram of FIG. In this embodiment, the output circuit 2
The connection point between 1 and the wiring 16 is the main reflection point. That is, by determining the length between this connection point and the connection point 26 between the terminating means 25 and the wiring 16 so that the signal transmission time is an integral multiple of half the signal switching period, jitter can be reduced. Can be minimal. The present invention is not limited to the wiring mounting structure shown in FIG. 7, but is generally applicable to a high-speed signal transmission wiring mounting structure having impedance mismatching points on the transmission side and the reception side of a signal transmission system that cause reflection. is there.

Next, another applied embodiment common to the above-described embodiment will be described with reference to FIGS. 6 and 7. FIG.

In the embodiment shown in FIG.
Instead, the configuration is provided in the second semiconductor device, and the other structures and effects are the same as those of the previous embodiment, and a description thereof will be omitted. According to the present embodiment, since the terminating means 25 is provided in the second semiconductor device, there is an effect that small mounting is possible.

The embodiment shown in FIG. 7 is different from the embodiment shown in FIG. 1 in that capacitors 61a and 61b are provided between the sending means 24 and the terminating means 25. According to this embodiment, in addition to the effects of the embodiment of FIG.
Since 0 and the receiving board 200 are connected only by alternating current, there is an effect that the DC voltages of the transmitting board 100 and the receiving board 200 can be used with different values.

[0027]

According to the above-described structure, the high-speed signal transmission wiring mounting structure in which each of the signal wiring substrates on the transmission side and the reception side has an impedance mismatching portion and both signal wiring substrates are connected by transmission lines. In order to reduce the effect of reflected waves due to the presence of impedance mismatching points, particularly reflected waves reciprocating in the transmission line connecting the signal wiring boards on the transmitting and receiving sides, connect the signal wiring boards on the transmitting and receiving sides. We defined the structure and length of the transmission line to be used, and realized a high-speed signal transmission wiring mounting structure that can reduce jitter.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention.

FIG. 2 is a perspective view of one embodiment of the present invention.

FIG. 3 is a diagram illustrating a relationship between a cable length and a jitter according to an embodiment of the present invention.

FIG. 4 is a circuit diagram of another embodiment of the present invention.

FIG. 5 is a circuit diagram of another embodiment of the present invention.

FIG. 6 is a circuit diagram of another embodiment of the present invention.

FIG. 7 is a circuit diagram of another embodiment of the present invention.

[Explanation of symbols]

11 ... substrate, 11a ... first substrate, 11b ... second substrate, 14 ... semiconductor package, 15a ... first semiconductor device, 15b ... second semiconductor device, 16 ... wiring, 16a ...
Output wiring, 16b Input wiring, 17 Connector, 18
Chip resistor, 19: through hole, 21: output circuit, 2
3 input circuit, 24 transmission end means, 25 termination means, 26
... input wiring branch, 41 ... output wiring branch, 61 ... capacitor, 71 ... mounting board, 100 ... transmission board, 200 ... reception board, 300 ... cable.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Yuyuki Shirai 6-16-16, Shinmachi, Ome-shi, Tokyo Inside the Device Development Center, Hitachi, Ltd. (72) Inventor Noboru 6-16, Shinmachi, Ome-shi, Tokyo F-term in Hitachi, Ltd. Device Development Center Co., Ltd. (reference)

Claims (4)

[Claims] 1. A transmission board comprising a first substrate on which a first semiconductor device having an output circuit is mounted, an output wiring connected to the output circuit, and a sending end means connected to the output wiring. A receiving substrate including a second semiconductor device having a circuit, a second substrate provided with an input wiring connected to the input circuit, and a termination unit connected to the input wiring;
A high-speed signal transmission wiring mounting structure comprising a cable connecting the output wiring and the input wiring, wherein an output impedance of the output circuit is different from a characteristic impedance of the output wiring, the cable and the input wiring. The round-trip transmission time of a signal that is matched to the reflected wave and propagates between the connection point of the output circuit and the output wiring and the connection point of the input wiring and the terminating means is the switching cycle of the signal. A high-speed signal transmission wiring mounting structure characterized by being an integral multiple of. 2. A transmission board comprising a first substrate on which a first semiconductor device having an output circuit is mounted, an output wiring connected to the output circuit, and a sending end means connected to the output wiring are provided. A receiving substrate including a second semiconductor device having a circuit, a second substrate provided with an input wiring connected to the input circuit, and a termination unit connected to the input wiring;
In the high-speed signal transmission wiring mounting structure including the output wiring and the cable connected to the input wiring, the sending end resistance is mismatched with respect to a reflected wave, and a connection point between the sending end means and the output wiring. A high-speed signal transmission wiring mounting structure, wherein a round-trip transmission time of a signal propagating between the input wiring and a connection point of the terminating means is an integral multiple of a switching cycle of the signal. 3. A transmission board comprising a first substrate on which a first semiconductor device having an output circuit is mounted, and an output wiring connected to the output circuit, and a sending end means connected to the output wiring are provided. A receiving substrate including a second semiconductor device having a circuit, a second substrate provided with an input wiring connected to the input circuit, and a termination unit connected to the input wiring;
In the high-speed signal transmission wiring mounting structure including the output wiring and the cable connected to the input wiring, the maximum point of the impedance mismatch with respect to the reflected wave of the transmission board and the maximum of the impedance mismatch with respect to the traveling wave of the reception board. Wherein the round-trip transmission time of a signal propagating between the point and the point is an integral multiple of the signal switching period. 4. A first semiconductor device having an output circuit and a second semiconductor device having an input circuit are mounted, and a wiring connecting the output circuit and the input circuit is provided. A high-speed signal transmission wiring mounting structure comprising: a substrate provided with transmitting means connected to the wiring; and a substrate provided with a terminating means connected to the wiring near the input circuit; a connection point of the output circuit, the transmitting means and the wiring; Among them, the maximum point of impedance mismatch with respect to the reflected wave, and the round-trip transmission time of the signal propagating between the wiring and the connection point of the terminating resistor, is an integral multiple of the signal switching period, High-speed signal transmission wiring mounting structure.