JPH11252185A - Signal transmission circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit a high speed signal without deterioration the waveform of the signal even in a CMOS-type driving circuit by connecting a series circuit composed of a terminal resistance and a coil to the reception terminal-side of a signal transmission line in parallel. SOLUTION: A signal transmission lines 14 are connected to the output terminals T1 and T2 of a driving circuit 13 constituted of field effect transistors FET1 -FET3 installed in a main circuit 10 constituted of a CMOS-type circuit. A signal is transmitted to the unit B of a reception side through the signal transmission line 14. The series circuit constituted of a terminal resistance R7 and a coil L1 is connected to reception terminals T3 and T4 in parallel. Thus, the rounding of the rise/fall waveforms of a rectangular wave to be transmitted is dissolved and the deterioration of the waveform is suppressed. Thus, the correct waveform can be transmitted to a reception circuit even if it is driven by the CMOS-type driving circuit, and the form of the board of a unit on a transmission side can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a signal transmission circuit that can be used for various electronic devices.

[0002]

2. Description of the Related Art In general, CMOS type semiconductor integrated circuits are mainly used for digital ICs and the like, since power consumption is small, the degree of integration is high, and the size can be reduced. Therefore, the inside of each unit of the electronic device is mainly a CMOS IC.
It is usually constituted by

In an electronic device, an ECL device is used as a circuit for outputting a signal to a signal transmission line in a signal transmission circuit for exchanging signals between units, for example. That is, as shown in FIG. 4, in a signal transmission circuit for transmitting a signal from the unit A to the unit B, the main circuit 10 of the unit A is constituted by an IC constituted by a CMOS type.
An ECL type driving circuit 12 composed of a CL circuit is arranged,
The signal transmission line 14 is connected through the ECL type driving circuit 12, and the reception side unit B is connected through the signal transmission line 14.
Is transmitting the signal. In the unit B on the receiving side, the receiving circuit 16 is also configured by an ECL circuit.

FIG. 5 shows an example of a specific circuit of the ECL type driving circuit 12. As is well known, the ECL circuit includes bipolar transistors Q ₁ , Q _{2, and the} like. In the example of FIG. 5, the bipolar transistors Q ₁ and Q ₂ form an emitter follower circuit, and the output terminal T of the emitter follower circuit
₁ and T ₂ , the signal transmission line 14 is connected, and the signal transmission line 1 is matched with a characteristic impedance of, for example, 50Ω.
4 is driven, and a circuit configuration for transmitting a signal to the unit B on the receiving side is shown.

Note that R₁Is the load resistance of the emitter follower
Vessel, R_TwoIs a resistor for impedance matching, R_ThreeIs the end
The resistance is shown. With this circuit configuration, the unit
A output terminal T₁, T_TwoOutput waveform of FIG. 7A
Assuming that the receiving terminal T_Three, T_FourThe received waveform of
The waveform shown in FIG. 7B is obtained. This receiving terminal T_Three, T_Four
The received waveform at the output terminal T₁, T_TwoAlmost matches the transmission waveform of
And fluctuation of rising and falling timing and pulse
Width Pw ₁= Pw_TwoStable signal transmission without fluctuation
be able to. Especially, by using the ECL circuit,
Even if the number of signals is high, the signal can be
Can be transmitted stably.

On the other hand, when the signal transmission line 14 is driven at high speed by the CMOS type driving circuit 13 as shown in FIG. 6, the waveforms at the receiving terminals T ₃ and T ₄ are deteriorated as shown in FIG. 7C. , The rising timing and the falling timing fluctuate from the regular timing, and the pulse width also becomes Pw ₁ >
An inconvenience of narrowing such as Pw ₃ occurs. This waveform deterioration is caused by the fact that the active elements of the CMOS type driving circuit have relatively large on-resistance of the field effect transistors FET ₁ , FE
This is considered to be due to the fact that it is composed of T ₂ , FET _{3 and the} like, and that the output impedance of the drive circuit composed of these field effect transistors FET ₁ , FET ₂ and FET ₃ is high.

[0007]

As described above, the EC
When the L-type drive circuit 12 is used, even a high-speed signal can be transmitted without deteriorating the signal waveform. However, since the ECL drive circuit 12 must be mounted on the unit A side, there is a disadvantage that the component mounting density on the board constituting the unit A cannot be increased. That is, since the ECL circuit has a relatively large shape, if the number of channels of a signal to be transmitted is large, the occupied area occupied by the ECL drive circuit 12 becomes large, and the size of the board becomes large.

On the other hand, when the CMOS type driving circuit 13 shown in FIG. 6 is used, the signal transmission line 14 can be directly driven from the main circuit 10, so that the advantage that the board shape can be reduced is obtained. However, the CMOS type driving circuit 13
As described above, there is a disadvantage that the signal waveform is significantly deteriorated for a signal having a high frequency as described above, and the signal cannot be put to practical use. SUMMARY OF THE INVENTION An object of the present invention is to provide a signal transmission circuit capable of transmitting a high-speed signal without deteriorating a waveform even in a CMOS type driving circuit.

[0009]

According to the present invention, a signal transmission line is connected to an output terminal of a CMOS type driving circuit, and a CMOS type driving circuit is provided.
In a signal transmission circuit for transmitting a signal to a receiving unit by a mold driving circuit, a series circuit composed of a terminating resistor and a coil is connected in parallel to a receiving terminal of the signal transmission line.

The inductance value L of the coil is f, the frequency of the signal to be transmitted, and ΔV, the voltage to be compensated.
Then, L = ΔV / 2πf. According to the configuration of the present invention, the coil resonates at the frequency of the signal to be transmitted, and the frequency characteristic of the signal transmission line emphasizes the gain on the high frequency side. As a result, the rounding of the rising and falling waveforms of the rectangular wave to be transmitted is eliminated,
Waveform deterioration is suppressed. As a result, the correct waveform can be transmitted to the receiving circuit even when driven by the CMOS type driving circuit, and the advantage that the shape of the board of the unit on the transmitting side can be reduced is obtained.

[0011]

FIG. 1 shows an embodiment of a signal transmission circuit according to the present invention. Parts corresponding to those in FIG. 6 are denoted by the same reference numerals. Field effect transistor FET ₁ which is provided in the configured main circuit 10 in the CMOS circuit in the present invention, FET _2, FET ₃ such as the signal transmitted to the output terminal T ₁ and T ₂ of the configured drive circuit 13 by connect the line 14, the series circuit composed of the signal transmission circuit for transmitting a signal to the unit B of the receiving side through the signal transmission line 14, and the terminating resistor R ₇ to the reception terminal T ₃ and T ₄ and the coil L ₁ Are connected in parallel. Termination resistor R ₇ shown in FIG. 1 is a resistance of the terminating resistor R ₆ shown in FIG. 6 divided into two parts, connect a terminator R ₇ divided to 1/2 of the resistance across the coil L _1, these 3 shows the case of the configuration of connecting the series circuit consisting of pieces of element between the receiving terminals T ₃ and T _4.

The inductance value L of the coil L ₁ is f, the frequency of the signal to be transmitted, and ΔV, the compensation voltage for improving the waveform of the rectangular wave to be transmitted (see FIG. 2).
Is given by L = ΔV / 2πf. Coil L
By setting the inductance value L of ₁ to an appropriate value, the coil L can be adjusted with respect to the frequency f of the signal to be transmitted.
₁ resonates, and the frequency characteristic of the signal transmission line 14 is the frequency f
It is emphasized in. Therefore, when a signal having the waveform shown in FIG. 3A is output to the output terminals T ₁ and T ₂ , the reception terminals T ₃ and T ₂
The T ₄ could be obtained waveform shown in Figure 3B. FIG. 3B
3A has almost the same rising and falling timings as the transmission waveform shown in FIG. 3A. Also, the pulse width PW was almost the same as the transmission waveform, and a correct waveform could be transmitted to the unit B on the receiving side.

[0013]

As described above, according to the present invention, even when the signal transmission line 14 is driven at a high speed by a CMOS-type IC driving circuit composed of a highly integrated circuit, the waveform on the receiving side unit B is not changed. Could be transmitted without deteriorating the signal. Coil L ₁ is the inductance value higher the frequency of the signal to be transmitted is reduced, as a result, the coil L ₁ can be made inexpensive.
Therefore only by adding inexpensive parts L _1, it is possible to practically the CMOS type drive circuit, it has the advantage that thereby reduce the shape of the transmitting side unit A is obtained.

[Brief description of the drawings]

FIG. 1 is a connection diagram for explaining an embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of the present invention.

FIG. 3 is a waveform diagram similar to FIG. 2;

FIG. 4 is a block diagram for explaining a conventional technique.

FIG. 5 is a connection diagram for explaining a circuit structure for driving a signal transmission line by an ECL type driving circuit.

FIG. 6 is a connection diagram for explaining a circuit structure for driving a signal transmission line by a CMOS type driving circuit.

FIG. 7 is a waveform chart for explaining the operations of FIGS. 5 and 6;

[Explanation of symbols]

10 main circuit composed of a CMOS-type circuit 14 the signal transmission line T _1, T ₂ output terminals T _3, T ₄ reception terminal R ₇ terminating resistor L ₁ coil

Claims (1)

[Claims] 1. A signal transmission circuit for connecting a signal transmission line to an output terminal of a CMOS type driving circuit formed in a CMOS type semiconductor integrated circuit device and transmitting a signal to another unit through the signal transmission line. A signal transmission circuit, wherein a circuit in which a terminating resistor and a compensation coil are connected in series to a receiving terminal of the unit is connected in parallel.