JPH066389A - Electronic circuit device - Google Patents

Abstract

PURPOSE:To reduce the number of transmission lines by equalizing the impedance of a reception side electronic circuit as seen from a transmitting circuit for threshold voltage supply or transmitting circuit for digital signal voltage supply. CONSTITUTION:The threshold voltage which is generated on the side of a transmission-side electronic circuit 1 is transmitted by a transmitting circuit composed of a cable as a common threshold voltage to negative-logical-level input terminals 6 of plural reception-side electronic circuit 2. At this time, the threshold voltage is attenuated to the same extent as digital signal voltages transmitted from plural positive-logical-level output terminals 3 of the circuit while transmitted through the line 11. Here, a terminating resistance 10 is provided at a terminal 6 of the circuit 2 to equalize the impedance of the circuit 2 as seen from the line 11 for threshold voltage supply to the circuit 2 to the impedance as seen from each transmission line for digital supply to the circuit 2. Then, the threshold voltage can be supplied and distributed to the circuits 2 by one line 11, so the number of the transmission lines can be decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic circuit device for transmitting and receiving a digital signal voltage using an unbalanced transmission line in which the number of transmission lines can be reduced as compared with a balanced transmission line, and more particularly to an electronic circuit device. The present invention relates to an electronic circuit device in which an operation margin (difference between a digital signal voltage and a threshold voltage) is prevented by changing a threshold voltage in accordance with a voltage fluctuation of a digital signal voltage.

[0002]

2. Description of the Related Art Conventionally, there are three methods of connecting an electronic circuit for transmitting a digital signal and determining whether the digital signal is at a positive logic level or a negative logic level by comparing it with a threshold voltage. Is often used. The connection method of these three types of electronic circuits is shown in FIG.
~ Shown in FIG.

FIG. 6 is a diagram showing a case of balanced transmission.
A positive logic level digital signal and a negative logic level digital signal are transmitted by two transmission lines having the same structure. In FIG. 6, 21 is a transmission electronic circuit, 22 is a reception electronic circuit, 23 is a positive logic level output terminal, 24 is a negative logic level output terminal, 25 is a positive logic level input terminal, 2
Reference numeral 6 is a negative logic level input terminal, and 27 and 28 are transmission lines having the same structure.

In this connection method, the input terminals 25, 2
The two voltages input to 6 are 180 degrees out of phase. At this time, since the input voltage of the input terminal 26 becomes the threshold voltage of the receiving electronic circuit 22 and the input voltage of the input terminal 25 becomes the digital signal voltage, the difference between the logical amplitude levels of the threshold voltage and the digital signal voltage becomes 2 times the logical amplitude level of, and the operation margin increases.

However, in this balanced transmission, since it is necessary to transmit both the digital signal voltage and the threshold voltage, two transmission lines are required to transmit one set of digital signals. Therefore, to send n sets of digital signals, 2n transmission lines are required.
Obstacles to achieving large scale, high density packaging.

Therefore, the unbalanced transmission shown in FIGS. 7 and 8 is used for the purpose of reducing the number of transmission lines by half. In FIG. 7 and FIG. 8, only the digital signal is transmitted from the transmitting electronic circuit 21 to the receiving electronic circuit 22 via the transmission line 27, and the threshold voltage V
t is created inside the receiving electronic circuit 22. The threshold voltage Vt is applied directly to the input terminal 26 of the receiving electronic circuit 22 by directly dividing it in the circuit shown in FIG. 7 and dividing it by the resistor 29 in the circuit shown in FIG.

[0007]

According to the methods shown in FIGS. 7 and 8, the number of transmission lines can be reduced by half, but the threshold voltage is reduced by the receiving electronic circuit 22.
Since it is supplied from the above, when the transmission loss of the transmission line for transmitting the digital signal is large, there arises a problem that the operation margin is reduced. That is, even if the digital signal is attenuated by the transmission loss of the transmission line, the threshold voltage has a constant value, so that the difference between the digital signal voltage and the threshold voltage is reduced. Therefore, when a digital signal is transmitted over a long distance or when it is transmitted through a high resistance transmission line, there arises a problem that the possibility of erroneously recognizing whether the digital signal is at a high level or a low level increases.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to achieve a reduction in the number of transmission lines by using an unbalanced transmission line and to reduce the transmission loss of the transmission line with an operating margin. It is an object of the present invention to provide an electronic circuit device that is not affected by the above.

[0009]

To this end, the present invention has a function of comparing an input digital signal voltage with a threshold voltage to determine whether the level of the digital signal voltage is a high level or a low level. An electronic circuit device comprising one reception-side electronic circuit and a transmission-side electronic circuit that supplies the digital signal voltage to the reception-side electronic circuit as a pair, and the pair is composed of two or more, The threshold voltage is distributed and supplied from any one of the plurality of transmission side electronic circuits to the plurality of reception side electronic circuits by using a transmission line having the same structure as the transmission line of the digital signal voltage, Moreover, the impedance seen from the receiving side electronic circuit from the transmission line for supplying the threshold voltage and the receiving side voltage from the transmission line for supplying the digital signal voltage. It was constructed by setting the same value as the impedance viewed circuit.

[0010]

In the present invention, when the transmission loss of the transmission line is large, not only the digital signal voltage but also the threshold voltage drops. Therefore, the transmission loss is similarly received, and the difference between the two is not changed, and the operation is performed. The margin does not decrease. Further, when there are n receiving side electronic circuits and n transmitting side electronic circuits, the number of transmission lines is only n for digital signal transmission and one for threshold voltage transmission. When n is 2 or more, the number of transmission lines can be significantly reduced as compared with balanced transmission.

[0011]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a block diagram of an embodiment applied when a digital signal is transmitted between high speed transmission units by a cable. Reference numeral 1 is a transmitting side electronic circuit, and 2 is a receiving side electronic circuit. 3 is a positive logic level output terminal of the transmission side electronic circuit 1, and 4 is a negative logic level output terminal (not used here). Reference numeral 5 is a positive logic level input terminal of the receiving side electronic circuit 2, and 6 is a negative logic level input terminal. Two
A threshold output terminal 7 is provided in one of the transmitter electronic circuits 1. Reference numeral 8 is a cabinet in which the high speed transmission unit is mounted, and 9 is a high speed transmission unit. Reference numeral 10 denotes an impedance matching terminating resistor, which is connected to the negative logic level input terminal 6 of the receiving side electronic circuit 2.

In the embodiment of FIG. 1, one threshold voltage created on the side of one transmitter electronic circuit 1 is converted into a negative logic level of a plurality of receiver electronic circuits 2 by a transmission line 11 made of a cable. It is transmitted as a common threshold voltage to the input terminal 6. At this time, since the threshold voltage is attenuated during transmission on the transmission line 11 to the same extent as the digital signal voltage transmitted from the plurality of positive logic level output terminals 3 of the transmission side electronic circuit 1,
In the receiving side electronic circuit 2, the difference (ratio) between the digital signal voltage and the threshold voltage is not affected, and the operation margin does not decrease.

Further, since the terminating resistor 10 is provided at the negative logic level input terminal 6 of the receiving side electronic circuit 2 which receives the threshold voltage, the receiving side electronic circuit 2 is thereby provided from the transmission line for supplying the threshold voltage. Can be made to coincide with the impedance of the receiving side electronic circuit 2 seen from the transmission lines for supplying digital signals.

A large number of printed wiring boards 12 are mounted on the high-speed transmission unit 9, and a large number of the reception side electronic circuits 2 or the transmission side electronic circuits 1 described above are mounted on each printed wiring board 12. Therefore, since a large number of cables for connecting the receiving side electronic circuit 2 and the transmitting side electronic circuit 1 are required between the plurality of high speed transmission units 9, the present invention can be applied to the cable transmission between these high speed units. The number of cables and the number of core wires can be reduced.

In general, the transmission line 11 between the high-speed transmission units 9 has a long distance and the signal loss in the cable increases. Therefore, by applying the present invention, it is possible to transmit a digital signal with a large operation margin. .

Next, FIG. 2 shows an embodiment in which the present invention is applied to digital signal transmission between chips of the multi-chip module 13. In FIG. 2, 14 is a transmitting side electronic circuit made of a semiconductor chip, 15 is a receiving side electronic circuit made of a semiconductor chip, and a plurality of electronic circuits 14 and 15 are mounted. In this multi-chip module 13, since it is necessary to make the transmission line 11 between the chips highly dense for miniaturization, the width of the wiring pattern becomes narrow and the resistance value of the transmission line inevitably increases. By applying the present invention to the transmission line 11 of such a multi-chip module 13, it becomes possible to transmit a digital signal with a large operation margin.

Next, FIG. 3 shows an embodiment in which the present invention is applied to the transmission of digital signals in the unit. In FIG. 3, reference numeral 16 is a motherboard, and this motherboard 16
Many printed wiring boards 17 are mounted on. A large number of transmitting side electronic circuits 1 and receiving side electronic circuits 2 are mounted on the printed wiring board 17. Therefore, the transmission line 11 for connecting the transmitting side electronic circuit 1 and the receiving side electronic circuit 2 is required on the mother board 16. This motherboard 1
Although the transmission line 11 on 6 may reach several tens of cm and the transmission loss increases, the application of the present invention enables transmission of a digital signal with a large operation margin.

Next, in the case where a plurality of receiving side electronic circuits 2 and a plurality of transmitting side electronic circuits 1 are formed on one printed wiring board 18 and these are connected to each other by a transmission line 11 on the same printed wiring board 18. FIG. 4 shows an embodiment to which the present invention is applied. In this embodiment, as in the case of the multichip module, the resistance value of the transmission line 11 increases due to the high density, but the application of the present invention enables the transmission of a digital signal with a large operation margin.

When the number of the reception side electronic circuit 2 and the transmission side electronic circuit 1 is n (n is an integer of 2 or more), 2n transmission lines are required for balanced transmission. In each of the embodiments described above, since n + 1 is sufficient, the number of transmission lines can be reduced. Further, compared with the conventional unbalanced transmission, it is possible to improve that the difference between the digital signal voltage and the threshold voltage decreases even if the resistance value of the transmission line increases.

Here, one transmission side electronic circuit and one reception side electronic circuit are used, and the digital signal and the threshold voltage are transmitted through this transmission line with the length of the transmission line having a distributed constant as a variable. Compare the waveforms when you do. Waveforms are simulators that can analyze distributed constant lines (for this type of simulator, see "Matsui, Mikazuki:
[Trends in design technology of printed wiring boards for predicting noise amount], EMC 1990.10.5, pp. 35-4
6 ". ) Is used to calculate. An ECL element is used for the transmission side electronic circuit and the reception side electronic circuit, and each input terminal of the reception side electronic circuit is terminated with 50Ω.

The resistance of each constant of the transmission line is 233 (Ω /
m), the inductance is 3.27 × 10 ⁻⁷ (H / m),
When the capacitance is 9.71 × 10 ^-11 (F / m) and the conductance is 1.0 × 10 ^-12 (S / m), the output waveform of the transmission side electronic circuit when the length of the transmission line is changed ( FIG. 5 shows A1: digital signal, B1: threshold voltage) and the input waveform (A2: digital signal, B2: threshold voltage) of the receiving side electronic circuit.

In the receiving side electronic circuit, the digital signal voltage is compared with the threshold voltage, and if the digital signal voltage is equal to or higher than the threshold voltage, the high level digital signal is input, and in the opposite case, the low level digital signal is input. It is determined that a digital signal has been input.

In FIG. 5, the length of the transmission line is from 1 cm to 2 cm.
It can be seen that even when the length is increased to 0 cm, the input digital signal A2 and the input threshold voltage B2 are similarly attenuated, and transmission with a large operation margin can be performed.

[0024]

As described above, in the present invention, the threshold voltage is supplied from the electronic circuit on the transmitting side for transmitting the digital signal through one transmission line, and the threshold voltage is supplied to the receiving end in plural numbers. Since it is distributed and supplied to the receiving side electronic circuit, it is possible to avoid a decrease in the operating margin due to the transmission loss of the transmission line. Further, the number of transmission lines can be significantly reduced as compared with balanced transmission.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment in which the present invention is applied to cable transmission between high speed transmission units.

FIG. 2 is an explanatory diagram of an embodiment in which the present invention is applied to digital signal transmission between chips of a multichip module.

FIG. 3 is an explanatory diagram of an embodiment in which the present invention is applied to digital signal transmission between printed wiring boards in a unit.

FIG. 4 is an explanatory diagram of an embodiment in which the present invention is applied to digital signal transmission between electronic circuits on a printed wiring board.

FIG. 5 is an explanatory diagram of a signal change due to a transmission loss of a transmission line.

FIG. 6 is an explanatory diagram of a conventional threshold voltage supply using balanced transmission.

FIG. 7 is an explanatory diagram of a conventional threshold voltage supply using unbalanced transmission.

FIG. 8 is an explanatory diagram of a conventional threshold voltage supply using unbalanced transmission.

[Explanation of symbols]

1: Electronic circuit of transmitting side, 2: Electronic circuit of receiving side, 3: Positive logic level output terminal, 4: Negative logic level output terminal, 5: Positive logic level input terminal, 6: Negative logic level input terminal, 7: Threshold Voltage output terminal, 8: Cabinet,
9: High-speed transmission unit, 10: Terminating resistor, 11: Transmission line, 12, 13: Printed wiring board, 14: Electronic circuit on transmission side made of semiconductor chip, 15: Electronic circuit on reception side made of semiconductor chip, 16: Motherboard, 17, 18:
Printed wiring board. 21: Transmission side electronic circuit, 22: Reception side electronic circuit, 23: Positive logic level output terminal, 24: Negative logic level output terminal, 25: Positive logic level input terminal, 2
6: Negative logic level input terminal, 27, 28: Transmission line, 2
9: resistance. A1: output digital signal voltage, A2: input digital signal voltage, B1: output threshold voltage, B2: input threshold voltage.

Claims (1)

[Claims] 1. A receiver electronic circuit having a function of comparing an input digital signal voltage with a threshold voltage to determine whether the level of the digital signal voltage is a high level or a low level, and In an electronic circuit device in which one transmitting electronic circuit that supplies the digital signal voltage to the receiving electronic circuit is paired, and the pair is two or more, the threshold voltage is set to the digital signal voltage A transmission line having the same structure as the transmission line is used to distribute and supply from any one of the plurality of transmission side electronic circuits to the plurality of reception side electronic circuits, and from a transmission line for supplying a threshold voltage. The impedance of the receiving side electronic circuit and the impedance of the receiving side electronic circuit seen from the transmission line for supplying the digital signal voltage are the same. Electronic circuit device, characterized in that set to a value.