JPH11234111A - Driver circuit and integrated circuit having the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To realize a driver circuit capable of selecting interface specifications of TTL specifications and ECL specifications,
It provides a circuit system that can support a variety of interface specifications even in small-scale production and that can support a wide range of applications. SOLUTION: An ECL driver circuit and a TTL driver circuit are provided side by side, and a drive transistor Q91 in an upper stage of the TTL driver circuit is shared as a drive transistor of the ECL driver circuit. The ground power supply VEE2 side of the TTL driver circuit is provided separately from the ground power supply VEE of the entire circuit. If the voltage applied to the ground power supply VEE2 is VEE, it operates as a TTL driver, and if it is about VCC to VCC-1V, the TTL driver operates. The circuit stops and operates as an ECL driver circuit. The interface signal is output from a common output terminal 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a circuit for interfacing an integrated circuit (IC).

[0002]

2. Description of the Related Art Generally, TTL / CM is used as a logic IC.
The OS family and the ECL family are well known. Each of these families has a unique logic level, and a connection between different levels has to use an IC for level conversion. This is because the specifications of the logic levels between the families are greatly different, and driver circuits that change the output form corresponding to the selected logic level among a plurality of logic levels have been put to practical use. Did not.

FIG. 4 shows a conventional ECL (Emitter Coupled Lo).
gic) An example of a driver circuit, which has an internal input terminal Xi
Signals input from n and Yin are level-converted and output as interface signals from an output terminal 20 drawn from the emitter of a transistor Q91 constituting an output stage of the ECL driver circuit.

FIG. 5 shows a conventional TTL (Transistor-T).
ransistor Logic) An example of a driver circuit, in which signals input from the internal input terminals Xin and Yin are extracted from a connection point between the emitter of the transistor Q91 and the collector of the transistor Q92 constituting the output stage of the TTL driver circuit. The output terminal 30 performs level conversion as an interface signal and outputs the signal.

Now, under the above-mentioned situation, a specific I
In C, it frequently occurs that an interface is used in accordance with the TTL specification or an interface is used in accordance with the ECL specification, depending on the connected device. Therefore, it is necessary to produce an IC in which only the driver circuit is changed in order to correspond to each interface specification, which is extremely inefficient especially in small-quantity production. On the other hand, ICs used by users
However, if the output is not performed according to the interface specification that matches the device, a conversion circuit for matching the output must be provided, which is complicated and increases the cost.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a driver circuit capable of outputting from a same output terminal with a selected one of a plurality of interface specifications,
It is an object to provide an IC including the driver circuit.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a TTL driver circuit and an ECL.
A driver circuit, including a power input terminal for selecting one of the two driver circuits, and an output terminal common to the two driver circuits, and applying a predetermined voltage to the power input terminal; A driver circuit in which an interface signal is output from the selected driver circuit to the output terminal.

Further, a transistor in the output stage of the ECL driver circuit is shared with one transistor in the output stage of the TTL driver circuit to constitute a driver circuit.

[0009] Further, the above object is solved by forming an integrated circuit having the above driver circuit.

A TTL driver circuit and an ECL driver circuit are built in an IC, a driver circuit is selected according to a voltage applied from a power input terminal, and an interface signal created by the driver circuit is output in common. Output from the terminal.

[0011]

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG. Here, FIG. 1 is a diagram showing the configuration of a driver circuit for both the TTL specification and the ECL specification according to the present invention, and FIG. 2 is a diagram for explaining the ECL operation of the driver circuit for both the two. FIG. 3 is a diagram for explaining the TTL operation of the driver circuit for both uses.

Normally, in a TTL driver circuit of a bipolar IC, two output transistors are vertically connected, and when the output is "L", the lower transistor is turned on and the upper transistor is turned off, while the output is "H". Sometimes the upper transistor is ON and the lower transistor is O
An interface signal is output by acting as an FF. In the ECL driver circuit, one output transistor is used as an emitter follower to output an interface signal.

In the embodiment of the present invention, as shown in FIG. 1, a TTL driver circuit and an ECL driver circuit are provided side by side, and the upper transistor Q91 of the TTL driver circuit is shared with the ECL driver circuit. And
When used as a TTL driver circuit, the upper and lower transistors Q91 and Q92 are operated together, while as an ECL driver circuit, the operation of the lower transistor Q92 is stopped.
Only the upper transistor Q91 is operated and used.

That is, if the potential of the power supply input terminal 11 is set to the ground potential VEE of the TTL driver circuit, the upper and lower transistors Q91 and Q92 become operable and function as a TTL driver circuit. Further, by setting the potential of the power supply input terminal 11 higher than the ground potential VEE of the TTL driver circuit and setting the potential at which the lower transistor Q92 stops operating, it functions as an ECL driver circuit.

As described above, the driver circuit of the present invention uses the TTL specification according to the potential applied to the power input terminal 11,
Alternatively, it becomes possible to output the interface signal of the ECL specification from the common output terminal 10. Incidentally, in an ordinary IC, the area for forming the output transistors Q91 and Q92 is generally several tens of times that of the other transistors.

Next, the operation of the driver circuit of the present invention will be described. First, the operation as an ECL driver circuit will be described with reference to FIG. V1 is an external power supply voltage VCC, which is usually about 3 to 5V. V2 is an offset external power supply of about 0 to 1 V connected between the power supply input terminal 11 and the external power supply, whereby no current flows to the block within the broken line in FIG. Accordingly, the signal applied to the internal input terminals Xin and Yin is emitter-followed by the transistor Q91 and appears as an output to the load resistor RL because only the upper ECL driver circuit can operate.

At this time, the base potential of transistor Q91 drops by the value of voltage R55 × iR55 due to resistor R55 and current iR55 inserted into the base to share transistor Q91. However, the resistance value of the resistor R54 and the resistance value of the resistor R55 between the power supply Vcc and the resistor R55 are generally the same in the number of digits,
The current iR54 flowing through 54 is in the relationship of iQ91b << I54 <I54 + iR55 = iR54, and since the TTL driver circuit is not operating, iR55 = iQ91b << iR54. The effect of inserting is negligible.

As for the "H" and "L" levels of the ECL output, if the current amplification factor of the transistor Q91 is represented by hFEQ91 and the output terminal current is represented by IOUT, the output Vout at the time of the output "H" is Vout = VCC- (R54 + R55). × iQ91b−VBEQ91 ≒ VCC− (R54 + R55) × IOUT / hFEQ91−VBEQ91 Also, the output Vout when the output is “L” is Vout = VCC− (R54 × iR54 + R55 × iQ91b) −VBEQ91 ≒ VCC− (R54 × I54 + R55 × IOUT / HFEQ91) -VBEQ91. Here, VBEQ91 is a base-emitter voltage of the transistor Q91.

Next, the operation as a TTL driver will be described with reference to FIG. In the TTL operation, VEE is supplied to the power supply input terminal 11, and the ECL driver circuit and the TTL
Both L driver circuits operate. That is, the above-mentioned EC
The transistor Q91 and the transistor Q92 operated by the L driver circuit are brought into a state of operating together.

When the signals applied to the internal input terminals Xin and Yin satisfy Xin> Yin, the output from the output terminal 10 is "H".
However, since the transistor Q20 and the transistor Q92 of the TTL driver circuit are both OFF and the transistor Q57 of the ECL driver circuit is also OFF, the output Vout at the time of the output “H” is Vout = VCC− (R54 + R55) × iQ91b− VBEQ91 ≒ VCC− (R54 + R55) × IOUT / hFEQ91−VBEQ91

On the other hand, when the signal applied to the internal input terminals Xin and Yin is Xin <Yin, the output from the output terminal 10 is "L", but the transistor Q of the TTL driver circuit
20, the transistor Q92, and the transistor Q57 of the ECL driver circuit are in the ON state. At this time, the transistor Q91 must be turned off so that the TTL output becomes “L” (normally 0.4 V or less). Therefore, the base potential of the transistor Q91 needs to be reduced to about 0.8V or less. This can be realized by flowing the collector current iQ20c of the transistor Q20 such that the base potential of the transistor Q91 = VCC-R54 * (I54 + iQ20c) -R55 * iQ20c≤0.8V.

Therefore, as described above, a driver circuit that can be used by switching between the TTL specification and the ECL specification can be constructed. By using this driver circuit in the output stage of the IC, the interface of the mating circuit to be connected can be configured. Connection is possible regardless of specifications.

When this driver circuit is used according to the ECL specification, the TTL driver connected to the voltage VEE is used to set the voltage VEE of the power supply input terminal 11 of the TTL driver circuit to the power supply voltage VCC to VCC-1V. The circuit does not operate, and no current flows in this part (broken line in FIG. 2). On the other hand, in the case of using the TTL specification, current also flows through the ECL driver circuit. However, since the bias current of the ECL driver circuit is extremely smaller than that of the TTL driver circuit, the power consumption of the entire IC increases. There is no danger.

Although there are two circuits, a TTL driver circuit and an ECL driver circuit, the number of output transistors which most affects the area on the IC layout can be made the same as that of the conventional TTL driver circuit. There is almost no increase in chip area.

It should be noted that the present invention is not limited to the above-described circuit configuration example, but may be any circuit configuration that realizes the technical idea of the present invention.

[0026]

As is apparent from the above description, according to the present invention, even if the interface specifications of the other device are different, it is possible to connect the devices without adding a conversion circuit to the outside. .

Also, since a single type of IC can cope with various interface specifications, especially in the case of small-quantity production.
The manufacturing efficiency is improved, and the management of ICs is also facilitated.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a driver circuit for both TTL specification and ECL specification according to the present invention.

FIG. 2 is a diagram for explaining an ECL operation of the dual-use driver circuit shown in FIG. 1;

FIG. 3 is a diagram for explaining a TTL operation of the dual-use driver circuit shown in FIG. 1;

FIG. 4 is a diagram for explaining an operation of a conventional ECL driver circuit.

FIG. 5 is a diagram for explaining an operation of a conventional TTL driver circuit.

[Explanation of symbols]

10, 20, 30 ... output terminal, 11 ... power supply input terminal, X
in, Yin: internal input terminal, V1: external power supply, V2: external power supply for offset

Claims (3)

[Claims] A TTL driver circuit; an ECL driver circuit; a power input terminal for selecting one of the two driver circuits; and an output terminal common to the two driver circuits. A driver circuit, wherein a predetermined voltage is applied to a power input terminal, and an interface signal is output from the selected driver circuit to the output terminal. 2. The driver circuit according to claim 1, wherein a transistor at an output stage of said ECL driver circuit is configured to be shared by one transistor of an output stage of said TTL driver circuit. 3. An integrated circuit comprising the driver circuit according to claim 1.