JP2608944B2 - Integrated multiple signal processing circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to suppression of crosstalk between channels in an integrated signal processing circuit such as an integrated circuit having a built-in multi-channel signal processing circuit.

[Conventional technology]

2. Description of the Related Art In a multi-channel signal processing circuit, integrated circuits are being promoted because of good matching between channels and tracking characteristics, miniaturization and cost reduction.

For example, the RGB video amplifier LM123 for a high definition color monitor described in National Semiconductor Linear Data Book 3 (1988) is a semiconductor integrated circuit having a contrast / brightness adjustment function and the like. In this integrated circuit, since the three-channel video circuit is integrated into one chip, the deviation of the voltage gain between channels is suppressed to ± 0.3 dB even in a wide contrast variable range of 40 dB.

[Problems to be solved by the invention]

However, the multi-channel integrated circuit has a problem that crosstalk between channels is large. For example, in the case of the above-mentioned conventional integrated circuit, in order to suppress the crosstalk to -40 dB or less, the video frequency must be limited to 10 MHz or less.

The cause of the increase in crosstalk between channels in a multi-channel integrated circuit is considered as follows. This will be described with reference to FIG. 2 showing a conventional example.

(A) Signal lines 22 for channels 2 and 3 and 4
And control signal line 21 for controlling each channel in common with 23, 24
Signal leakage via the parasitic capacitances 31 and 32, 33 at the intersections with.

(B) Signal leakage via the common impedances 43 and 44 between the power supply line 41 and the ground line 42 inside the integrated circuit 1.

Other possible causes include signal leakage through the inter-terminal capacitance of the integrated circuit, but the above two items are the main causes. Further, even if junction separation or insulation layer separation is performed on each channel to suppress crosstalk, the above-described causes cannot be eliminated.

SUMMARY OF THE INVENTION It is an object of the present invention to suppress crosstalk between channels in an integrated multiple signal processing circuit such as a multichannel integrated circuit.

[Means for solving the problem]

The above object is attained by employing at least one of the means represented by the following four items.

(A) In a signal line of at least one channel, a signal line at a position where a wiring provided from outside the channel to inside the channel intersects is a set of differential signal lines. At that time, the capacitance value of the parasitic capacitance between the wiring and each of the pair of differential signal lines caused by the intersection with the wiring is made substantially equal.

(B) A control signal line inevitable to intersect with a signal line of at least one channel is set as a differential control signal line, and control is performed by receiving a differential control signal by a differential input circuit. At this time, the capacitance value of the parasitic capacitance between the signal line and the differential control signal line caused by the intersection with the signal line is made substantially equal.

(C) Insert a series resistor into a control signal line that cannot avoid crossing the signal line of at least one channel.

(D) When a power line or a ground line impedance common to a plurality of channels is provided, a constant current source or a constant current circuit is inserted in series into a power line or a ground line of a signal circuit in at least one channel. .

[Action]

The operation of the means represented by the above four items will be described in the following four items corresponding to the respective item numbers.

(A) Parasitic capacitances of substantially equal capacitance between the wiring and each of the pair of differential signal lines are transmitted to each of the signals leaking from each of the pair of differential signal lines to the wiring. Make the functions approximately equal. Thereby, the signal leaking from the above-mentioned pair of differential signal lines to the above-mentioned wiring is almost canceled, and crosstalk to another channel can be suppressed.

(B) Parasitic capacitances of substantially equal capacitance between the signal lines and the differential control signal lines make signals leaking from the signal lines to the differential control signal lines approximately equal. The differential input circuit to which the differential control signal is input eliminates the influence of the leakage signal input as substantially equal in-phase signals. Thereby, crosstalk due to signal leakage to the differential control signal can be suppressed.

(C) The series resistor inserted into the control signal line forms a low-pass filter due to the distributed capacitance between the resistor and the ground potential. Therefore, when the frequency of the control signal is lower than the frequency of the leak signal, the signal leaked from the signal line to the control signal line can be removed,
Crosstalk can be suppressed via the control signal line.

(D) The constant current source or the constant current circuit has an action of suppressing a signal current flowing through a power supply line or a ground line impedance common to the plurality of channels.
Thereby, the crosstalk via the power supply line or the ground line impedance can be suppressed.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 3 shows an integrated circuit in which signal processing circuits of three channels of 2, 3 and 4 are built. The wiring 210 crosses three sets of the differential signal lines 221 and 222, 231 and 232, 241 and 242 in the above-mentioned channel. When the wiring 210 is a control signal line for controlling the channels 2 and 3 and 4, the one-dot broken lines 211 and 212 and 213
In the case of FIG. 3, the wiring 210 is not limited to the control signal line, and includes all wirings.

Since the following description is made with channel 2 as a representative, the same applies to the other channels 3 and 4. Parasitic capacitances 311 and 312 caused by the intersections of the wiring 210 and the differential signal lines 221 and 222, respectively. In order to explain an example of a method for making the capacitances of the parasitic capacitances 311 and 312 substantially equal, FIG. 4 shows a structural diagram of the integrated circuit near the intersection. In FIG. 4, reference numeral 60 denotes an SiO ₂ oxide film layer, 61 denotes a semiconductor layer made of Si or GaAs, etc., and the wirings 210 and 214, and the differential signal lines 221 and 222 are formed by multilayer wiring made of Al or polysilicon. (wiring
214 is used in another embodiment described later. The parasitic capacitances 311 and 312 are distributed capacitances parasitic between the wiring structures. However, due to the symmetry of the wiring structure, the intersection indicated by the hatched portion in FIG. 5 showing the top view of FIG.
By making the areas 2101 and 2102 equal, the capacitances of the parasitic capacitances 311 and 312 are almost equal. (Actually, there is a slight capacitance deviation due to the electric field caused by the semiconductor layer 61 and the influence of the peripheral wiring.) In FIG. 4, only the parasitic capacitance due to the intersection in the oxide film layer is discussed. The same capacitance value can be obtained in the same manner as described above with respect to the parasitic capacitance generated between the multi-layered wiring structures in the semiconductor device and the parasitic capacitance generated between the respective wiring structures of the oxide film layer and the semiconductor layer. Further, the above method can be easily applied to a hybrid integrated circuit.

By the parasitic capacitances 311 and 312 having substantially the same capacitance value obtained by the above method example, the transfer functions of the signals leaking from each of the differential signal lines 221 and 222 to the wiring 210 become substantially equal. As a result, the signal leaking from the differential signal lines 221 and 222 to the wiring 210 is almost cancelled. As a result, if the embodiment shown in FIG. 3 is used, signal leakage from the channels 2 and 3, 4 via the wiring 210 can be suppressed.

The embodiments described above are not limited to the three-channel built-in integrated circuit, and can be applied to a single-channel integrated circuit as well as a multi-channel built-in integrated circuit as a technique for suppressing crosstalk to peripheral circuits. Needless to say, it is not necessary to equalize the above parasitic capacitance values between channels. In addition, since the above-described embodiment limits only the points where signal lines and wirings intersect, signals in a range where there is no intersection may be transmitted in a balanced or unbalanced manner (FIG. 3).

Next, the second embodiment of the present invention will be described with reference to FIG. In FIG. 6, the control signal of the control line which must cross at least one of the signal lines 22 and 23 and 24 is a differential control signal using the differential control signal lines 210 and 214. And transmits the differential control signal to the differential input circuit 71.
And 72 and 73 to perform desired control. However, in each of the differential input circuits, the input impedances of the inverting input and the non-inverting input are equal or the differential control signal lines 210 and 2
The impedance of each of the fourteen is set to be equal. Also in this case, for example, the parasitic capacitances 313 and 314 generated by the intersections of the signal line 22 and the differential control signal lines 214 and 210 in the channel 2 are set to substantially equal capacitance values. The configuration method is the same as the case of the parasitic capacitances 311 and 312 shown in FIG.

The parasitic capacitances 313 and 314 substantially equalize signals leaking from the signal line 22 to the differential control signal lines 214 and 210, respectively. This is because the input impedance of each of the differential control signal lines 214 and 210 can be considered to be substantially equal at the signal leakage location.

Therefore, the leakage signal is removed as a common-mode signal in each of the differential input circuits 71, 72, and 73. As a result, by using the embodiment shown in FIG. 6, it is possible to suppress the crosstalk due to the signal leakage to the differential control signal.

It goes without saying that the above embodiment can be applied not only to a three-channel built-in integrated circuit but also to a multi-channel built-in integrated circuit. The present invention is also effective when the control signal line crosses only the signal line of one channel. It is also obvious that it is not necessary to equalize the parasitic capacitance value or the input impedance of the differential control signal line between the channels. (In general, the differential control signal line is a long wiring, and the input impedance at the intersection with the signal line of each channel may be different due to the influence of parasitic distributed impedance.) Further, the third embodiment of the present invention will be described. Will be described with reference to FIG. In FIG. 7, series resistors 81, 82 and 83 are inserted into a control signal line 21 which must cross at least one of the signal lines 22 and 23 and 24.

These series resistances, as represented by 81, form a low-pass filter by the distributed capacitance parasitic between the resistance and the ground potential. The parasitic distributed capacitance has a characteristic close to a proportional relationship with the resistor area in the resistance structure of the integrated circuit. Here, most of the signal leaking from the signal line to the control signal line 21 is occupied by a high-frequency signal via a parasitic capacitance due to crossing of wiring. Also, the control signal often has a low frequency. Therefore, it is preferable that the above-mentioned series resistance be made larger in the above-mentioned resistor area. Further, considering the influence on the control operation of the integrated circuit, it is preferable to lower the resistance value of the series resistor. These requirements for the series resistance are consistent with the resistance characteristics of the integrated circuit. Needless to say, the above consideration regarding the resistance does not depend on whether the integrated circuit is a semiconductor circuit or a hybrid circuit.

Therefore, by using the embodiment shown in FIG. 7, it is possible to remove the signal leaked from the signal lines 22, 23, and 24 to the control signal line 21.

Further, the series resistor can be inserted at an arbitrary position on the control signal line. For example, it is inserted between the channels built in the integrated circuit or inserted so as to sandwich the intersection of the control signal line and the signal line of each channel (in the latter case, it is inserted even in the channel having the intersection). , As well as measures against oscillation due to self-feedback).

As described above, by using the present invention, crosstalk via the control signal line can be suppressed. Further, it goes without saying that the above embodiments can be applied not only to a three-channel built-in integrated circuit but also to a multi-channel built-in integrated circuit.

The embodiment of the fourth aspect of the present invention will be described with reference to FIG. In FIG. 8, it is assumed that a common ground line 42 exists between the channels. Such a situation often occurs when the number of terminals of the integrated circuit is limited. In FIG. 8, constant current sources or constant current circuits 91 to 96 are inserted in series to the ground lines of the signal circuits 51 to 56 in each channel.

By using the above configuration, the signal current flowing to the ground line impedance 44 common to the channels can be suppressed, and crosstalk via the ground line impedance can be suppressed. Conversely, the number of power and ground terminals of the integrated circuit can be reduced while suppressing crosstalk.

In FIG. 8, when the signal current flowing through the power supply line of the above signal circuit is substantially equal to the current flowing through the ground line, the constant current source or the constant current circuits 91 and 92 are disconnected from the ground line side, It can be inserted in series in the same direction as before at 4311 and 4312 on each side.

Since the principle of the present invention is to suppress the signal current flowing in the power supply line or the ground line impedance common to the channels, all the signal circuits in each channel use a constant current source or a constant current circuit. It is not necessary to change the circuit configuration, and only the signal circuit having a large signal current flowing through the power supply line or the ground line needs to be changed. In addition, the constant current source and the constant current circuit used can be replaced with resistors as long as the signal current flowing through the common impedance between the channels does not increase.

Here, FIGS. 9 to 14 show examples of signal circuits in which 91 to 96 constant current sources or constant current circuits are inserted in series into a power supply line or a ground line. FIGS. 9 to 11 show examples in which the signal circuit is a differential amplifier circuit. Regardless of whether the emitter-to-emitter impedance is a connection between 5121 and 5122 (FIG. 9),
(FIG. 10), the embodiment can be applied to a differential amplifier circuit in which a constant current source or constant current circuits 91, 911, and 912 are inserted in series to a power supply line or a ground line. Similarly, regardless of the output impedance of the passive element 5125 or 5126 (No. 9
(Fig. 10 and Fig. 10), regardless of the active element 5127 or 5128 (Fig. 11).
FIG.

FIG. 12 shows a common-emitter amplifier circuit with a constant power supply or constant current circuit 91 as a load. Similarly, a common-grounded amplifying circuit (FIG. 13) and a common-base amplifying circuit using a constant-current source or a constant-current circuit as a load can be an embodiment. FIG. 14 shows a grounded base amplifier circuit in which a bias current is supplied by a constant current source or a constant current circuit.

In each of the circuit examples shown in FIGS. 9 to 14,
It goes without saying that the polarities of the power supply and the active element, the constant current source or the constant current circuit can be reversed. Each active element includes all elements that can be used in an integrated circuit such as various semiconductor elements such as FETs (including GaAs elements) in addition to transistors.

Finally, FIG. 1 shows an embodiment in which the first to fourth items of the present invention are simultaneously carried out, so that the characteristics of the present invention are best represented. In FIG. 1, a common ground terminal 12 is used for each channel. When the embodiment of FIG. 1 is applied to a video integrated circuit for a high definition display,
At a signal frequency of 100 MHz, crosstalk between channels could be suppressed to -44 dB or less.

Although the embodiments of the first to fourth aspects of the present invention have been described in detail above, it is needless to say that any of the embodiments can be applied to an integrated circuit. Can be implemented.

In general, the signal amplification frequency band of each channel of a multi-channel integrated circuit can be easily expanded by using a technique for broadening an integrated circuit including only a single channel (however, the power consumption of the integrated circuit and the package) The restrictions due to the number of terminals cannot be avoided). However, since the crosstalk between channels generally shows a characteristic that increases as the frequency increases, the usable frequency band of the multi-channel built-in integrated circuit has been limited. Therefore, by using the present invention, the frequency band of the multi-channel integrated circuit can be greatly expanded.

〔The invention's effect〕

As described above in detail, according to the present invention, there is an effect that crosstalk can be suppressed.

When the present invention was applied to a semiconductor integrated circuit, crosstalk between channels could be suppressed to -44 dB or less at 100 MHz.

By using the present invention, the frequency band of an integrated multiple signal processing circuit such as a multi-channel integrated circuit can be greatly expanded.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, FIG. 2 is a circuit diagram showing a conventional example, FIG. 3 is a circuit diagram showing another embodiment of the present invention, FIG. 4 and FIG. Explanatory diagram of the parasitic capacitance between the wirings,
FIG. 6 is a circuit diagram showing still another embodiment of the present invention, and FIG.
FIG. 9 is a circuit diagram showing still another embodiment of the present invention, FIG. 8 is a circuit diagram showing still another embodiment of the present invention, and FIGS.
FIG. 14 is a circuit diagram showing a specific example of the signal circuit shown in FIG. 1 integrated circuit 2,3,4 each channel 21,210,214 control signal line 22,221,222 signal line 71,72,73 differential input circuit 81,811,812 series resistance 91,92,911,912 constant current source or Constant current circuit.

Claims (4)

(57) [Claims] When at least one of a plurality of channels is a specific channel, a wiring provided from outside the specific channel to inside the specific channel crosses a signal line of the specific channel. In this case, the signal line portion at the intersection is formed of a set of differential signal lines, and each intersection between each signal line constituting the set of differential signal lines and the wiring is provided. Of each of the differential signal lines, the parasitic capacitance generated between each of the signal lines constituting the set of differential signal lines and the wiring is set to be substantially equal to each other. An integrated multiple signal processing circuit, wherein crosstalk with the wiring is prevented. 2. When at least one channel among a plurality of channels is set as a specific channel, two control signal lines which cannot be avoided at the intersection with the signal line of the specific channel are used. It is necessary to connect a differential input circuit with a common-mode signal suppression function for receiving and controlling the differential control signal to the differential control signal line. By making the area of each intersection between each control signal line constituting the differential control signal line and the signal line of the specific channel almost equal to each other, the differential control is performed. Assuming that each parasitic capacitance generated between each control signal line constituting the signal line and the signal line of the specific channel is a substantially equal capacitance value, the crosstalk generated between the signal line and the control signal line is the required value. System Integral multiple signal processing circuits, characterized in that it suppresses the influence on. 3. When at least one channel among a plurality of channels is a specific channel, one point on a control signal line crossing a signal line of the specific channel and the control signal line are connected to each channel. A low-pass filter composed of a resistor and a capacitor by connecting a resistance element with a distributed capacitance, such as a semiconductor resistor or a resistor on a surface mount circuit, between each of the connection points. Wherein the high-frequency signal component leaked from the signal line of the specific channel to the control signal line is attenuated by the low-pass filter. 4. A power supply line or a ground line common to a plurality of channels among a plurality of channels, and in all of the plurality of channels, all signal circuits in each channel and the power supply line or the ground line are provided. And a constant current source or a constant current circuit inserted in series between them to prevent crosstalk from leaking from a certain channel to another channel via the power supply line or the ground line. Integrated multiple signal processing circuit.