JPS597247B2 - semiconductor logic circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an integrated semiconductor logic circuit, and in particular to one that allows easy exchange of logic signals with different logic amplitudes between its inputs, outputs, or both. .

2. Description of the Related Art With recent advances in integration technology, large-scale dense integrated circuits (hereinafter referred to as LSIs) are becoming more common.

In LSI, many logic circuits are formed simultaneously on one semiconductor substrate (hereinafter referred to as a chip), so the gates within the chip are less susceptible to external noise. Therefore, in order to increase the speed of LSI, small logic circuits with a small noise margin are There is a tendency for a wide range of logic circuits to be used.

However, since the signal connections between LSI chips are one to two orders of magnitude longer than the length of the signal wiring within the chip, the influence of external noise cannot be ignored.

Therefore, the output level of the chip logic circuit is converted in the vicinity of the LSI chip to increase the logic amplitude and is supplied to the outside as a noise-resistant logic signal, and conversely, a signal with a large logic amplitude can be converted into a signal with a small logic amplitude. A method has been adopted in which the signal is converted into a signal and then supplied to the logic circuit of the LSI chip.

However, this method requires a level conversion chip in addition to the LSI chip, which increases the complexity of mounting when configuring the device, increases cost, and reduces packaging density.

The purpose of this invention is to provide a conversion function that can receive a signal with a large logic width as needed in the semiconductor integrated circuit itself in which a logic circuit is formed, or supply an output to an external logic circuit with a large logic width. An object of the present invention is to provide a semiconductor logic circuit having a semiconductor logic circuit.

According to the present invention, by applying a control signal to a control terminal prepared in advance on an LSI chip, it is possible to output a larger logic width to the output terminal and accept a larger logic width to the input terminal. done to.

For this reason, for example, in a current switching type logic circuit LSI chip using constant current sources, two constant current sources are prepared in the output logic circuit having an output terminal connected to the outside of the chip.
One of them is provided with a control terminal, and while one constant current source operates at all times, the other constant current source only operates when a specified constant voltage (control signal) is applied to the control terminal.

In this way, the current flowing through the load resistance of the output logic circuit can take one of two values, and when the current is increased, the logic level becomes a dog.

On the other hand, the input logic circuit that has an input terminal connected to the outside of the chip similarly has two constant current sources, one of which operates all the time, while the other operates only when a control signal is applied to the control terminal. However, depending on whether or not a control signal is supplied to the control terminal, the current flowing through the resistance element from which the reference voltage is obtained is switched between two values.

When a large current is passed through this, the reference voltage of the input logic circuit becomes large.

If necessary, the control terminals of the output logic circuit and the input logic circuit can be connected within the chip and taken out as a common control terminal outside the chip.

The invention will now be explained in detail with reference to the drawings.

Figure 1 is a diagram showing a specific example of a current switching type logic circuit using a constant current source.
, Q3, a load resistor R1R2 that generates a logic level, and constant current sources Q4, R3, and has input terminals 1 and 2, output terminals 3 and 4, a reference voltage terminal 5, and a constant current source reference voltage terminal 6.

To operate the logic circuit shown in FIG. 1, apply an appropriate constant voltage to the constant current source reference voltage terminal 6, operate the constant current circuit, and set the reference voltage terminal 5 to a level between logic levels "1" and "0". By applying a reference voltage and applying logic signal voltages to input terminals 1 and 2, an opposite-phase logic output is obtained at output terminal 3, and an in-phase logic output is obtained at output terminal 4.

It is clear that the output level (ie, logic amplitude) appearing at the output terminal 3 or 4 is determined by the constant current power supply Q4tR3 and the resistance values of the resistors R1 and R2.

FIG. 2 is a circuit showing a specific example of a reference voltage circuit that generates a reference voltage to be applied to the reference voltage terminal 5 of FIG.
It consists of a constant current source QstR5 having the same circuit configuration as shown in the figure and a resistor R4 from which a reference voltage is obtained.

Since the reference voltage is set between logic levels "1" and "0", if the current of the constant current source is the same as that in Figure 1, the resistance value of resistor R4 is half the resistance value of resistor R1 or R2. By selecting , the desired reference voltage can be easily obtained.

? FIG. 3 shows a specific example of a semiconductor logic circuit according to the present invention, and is a diagram schematically explaining a logic circuit within an LSI chip, and the outer solid line frame indicates the boundary of the LSI chip.

The logic circuits inside the LSI chip are input part logic circuit A whose input is connected to the outside of the chip, input part logic circuit A which has both input and output connected to the logic circuit inside the chip and does not go outside the chip, and logic circuit B whose output is connected to the outside of the chip. It can be divided into three types: C.

In FIG. 3, the dotted line commonly connected to the logic circuits A and C indicates the control line of the constant current source.

FIG. 4 is a diagram showing an example of a circuit configuration in which the present invention is applied to the logic circuit A in FIG. 1
Control terminals 12 are led out from the two constant current sources Q11 and R11, and the other constant current source QIO tR10 has a terminal 11 connected to a constant voltage that provides a constant current source reference voltage within the chip.

If a constant voltage (control signal) is not applied to the control terminal 12, the transistor Q1 is in a cutoff state, so the circuit of FIG. 4 operates in the same way as the logic circuit of FIG. 1.

That is, the reference voltage connected to the base of transistor Q3 is set at the center of the logic amplitude of the logic circuit of FIG. 1, providing a reference for small logic amplitudes.

The logic input voltage applied to input terminal 9 or 10 is increased (e.g. transistors Q6, Q7, Q7 in FIG.
(twice the logic width at the collector of Q8), the reference voltage of the logic circuit (base potential of transistor Q8) is logic
It will shift to the 1" side.

In other words, the reference voltage will be located at 1/4 of the logic amplitude, and will no longer operate as a correct reference voltage, resulting in a risk of malfunction.

However, when the control terminal 12 is connected to the constant current source reference voltage terminal 11, the transistor Qll also becomes conductive, and twice as much current flows through the resistor R8 that generates the reference voltage. The reference voltage is set at the center of the double logic width, and this logic circuit operates correctly.

That is, correct operation is possible when the level of the input logic signal is high.

In the example, we considered the input logic width to be twice, but it is not necessary to double the input logic width, and in order to generate a reference voltage according to the input logic width, you can change the value of the resistor R1. It is clear that it is possible to generate a reference voltage of .

Also, if you do not want to change the value of the resistor Rll, use the control terminal 12.
A similar effect can be obtained by changing the constant voltage applied to.

That is, it can be seen that the circuit shown in FIG. 4 allows logic amplitude conversion (level conversion) by controlling the control terminal 12.

FIG. 5 is a diagram showing an embodiment in which the present invention is applied to the output section logic circuit C of FIG. 3.

In this figure, there are two constant current sources Q15 t in the current switching circuit section.
The configuration has R15 t Qta tR16.

One constant current source Q159R15 has a control terminal 17, and the constant current source reference voltage terminals 18 of the other constant current sources Q16 and R16 are supplied with a constant voltage within the chip.

When no constant voltage (control signal) is applied to control terminal 17, the logic circuit of FIG. 5 operates at the same logic level as the logic circuit of FIG. If the resistance value of resistor R15 is made equal to the resistance value of resistor R16, the current switching circuit section will have 2
Double the current flows and therefore the logic amplitude appearing at the output terminal 15 or 16 also doubles.

In this explanation, a constant current circuit made up of a transistor Q15 and a resistor R15 is made up of a transistor Q16 and a resistor R16. Although the characteristic is considered to be the same as that of a constant current source, this is not necessarily necessary, and the logic width appearing at the output terminal 15 or 16 can be arbitrarily changed as in the case explained with reference to FIG.

That is, in FIG. 5, by applying or removing a control signal to the control terminal 17, the output logic amplitude of the output terminals 15 and 16 can be increased or decreased.

According to the semiconductor logic circuit according to the present invention described above, the current flowing through the resistor R8 from which the reference voltage is obtained or the load resistors R12, R12 is controlled to be activated or deactivated by the voltage control signal to the control terminal of the constant current source. It is possible to increase the reference voltage or increase the logic level in accordance with the logic amplitude of an external logic circuit connected to the chip.

Therefore, logic circuits can operate at low power and high speed inside the LSI chip, with very small logic widths and without using extra level conversion chips, and outside the chip, logic circuits can be operated with large logic widths. be able to.

Therefore, packaging density is increased, and since no extra level conversion chip is used, it is also possible to reduce costs.

Furthermore, by manufacturing an LSI chip according to the present invention, a small logic width can be achieved within an alumina substrate, such as a multi-chip LSI (an LSI configured by mounting a large number of chips on an alumina substrate interconnected with each other). Work,
Even when it is desired to operate with a large logic width outside the alumina substrate, the purpose can be easily achieved by short-circuiting the control terminal of the chip connected to the terminal of the alumina substrate and the constant current source reference constant voltage terminal. Therefore, there is no need to manufacture LSI chips with different logic widths, which has a large economic effect.

In the above description, L mainly uses NPN} transistors.
Although the operation of the present invention was explained using an SI chip, PNP }
The present invention can also be applied to LSI chips using transistors. Further, the present invention can also be applied to only one of the input logic circuit and the output logic circuit of an LSI chip.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram showing a conventional current switching circuit using a constant current source, Fig. 2 is a circuit diagram for generating a reference voltage, and Fig. 3 is a logic configuration of an LSI chip using a semiconductor logic circuit according to the present invention. FIG. 4 is a connection diagram showing an embodiment of the input section logic circuit of the semiconductor logic circuit according to the present invention.
FIG. 5 is a connection diagram showing an embodiment of the output section logic circuit of the semiconductor logic circuit according to the present invention. A... Input section logic circuit, C... Output section logic circuit.

Claims (1)

[Claims] 1. A semiconductor integrated circuit comprising at least one current switching type logic circuit that performs a logic operation based on a reference voltage and switches the current flowing through a current source as an input logic circuit and an output logic circuit on a single integrated circuit chip. In the circuit, an external control terminal provided on the chip is connected to the external control terminal, the external control terminal outputs a voltage of a first value when the external control terminal is at a first level, and the external control terminal outputs a voltage of a first value when the external control terminal is at a first level. a reference voltage generation circuit that outputs a voltage of a second value whose absolute value is larger than the first value when the level is , and the output voltage of the reference voltage generation circuit is applied as a reference voltage to the input logic circuit. and means connected in parallel to the current source in the output logic circuit, which do not function when the external control terminal is at the first level and supply a predetermined current when the external control terminal is at the second level. and an additional constant current source that outputs an additional constant current source, and by controlling the level of the external control terminal, the chip can be connected to signals of different logic amplitudes outside the chip. integrated circuit.