JPS6126252B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an integrated semiconductor logic circuit,
In particular, it relates to those whose inputs and/or outputs have different logic amplitudes, allowing easy exchange of logic signals.

With recent advances in integration technology, large-scale, densely structured integrated circuits (hereinafter referred to as LSI) are becoming increasingly common. In LSI, many logic circuits are formed simultaneously on one semiconductor substrate (hereinafter referred to as a chip).
In-chip gates are not easily affected by external noise, and therefore, in order to increase the speed of LSIs, there is a tendency to use logic circuits with small logic amplitudes and small noise margins. However, since the signal connections between LSI chips are 1 to 2 orders of magnitude longer than the signal wiring length 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 supplied to the outside as a noise-resistant logic signal, and conversely, a signal with a large logic amplitude is converted to a signal with a small logic amplitude. A method is adopted in which the signal is 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 costs, and reduces packaging density.

An object of the present invention is to provide a semiconductor integrated circuit in which a logic circuit is formed, which has a conversion function that can receive a signal with a large logic amplitude as needed, or supply an output to an external logic circuit with a large logic amplitude. To provide logic circuits.

According to the present invention, by applying a control signal to a control terminal prepared in advance on an LSI chip, a larger logic amplitude can be output to the output terminal, and a larger logic amplitude can be accepted to the input terminal. done to. For this reason, in a current-switching logic circuit LSI chip that uses constant current sources, two constant current sources are prepared in the output logic circuit that has an output terminal connected to the outside of the chip, and one of them is provided with a control terminal. Although one constant current source operates all the time, 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 resistor of the effluent logic circuit can take one of two values, and when the current is increased, the logic level is increased.

The invention will now be described 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, which includes current switching circuit transistors Q ₁ , Q ₂ , Q ₃ and load resistors R ₁ , R ₂ and Consisting of constant current sources Q ₄ and Q, input terminals 1 and 2, output terminals 3 and 4, reference voltage terminal 5,
It has 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 apply a voltage between the logic levels "1" and "0" to the reference voltage terminal 5. 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. The output level (i.e. logical amplitude) appearing at output terminal 3 or 4 is determined by constant current power supply Q ₄ ,
It is clear that it is determined by R ₃ and the resistance values of resistors R ₁ and R ₂ .

Figure 2 shows a specific example of a reference voltage circuit that generates a reference voltage to be applied to the reference voltage terminal 5 in Figure 1, and is a constant current source with the same circuit configuration as in Figure 1.
It consists of Q ₅ , R ₅ and a resistor R ₄ from which a reference voltage can be obtained. Reference voltage is logic level “1” and “0”
Since the voltage of the constant current source is set in the middle of
If it is the same as that in the figure, the resistance value of resistor R ₄ is the resistance
A desired reference voltage can be easily obtained by selecting half the resistance value of _R1 or _R2 .

Figure 3 shows one of the semiconductor logic circuits to which the present invention is applied.
It is a diagram showing a specific example and schematically explaining a logic circuit within an LSI chip, and the outer solid line frame indicates the boundary of the LSI chip. The logic circuit inside the LSI chip has an input section logic circuit A whose input is connected to the outside of the chip, and an input section logic circuit A whose input and output are both connected to the inside logic circuit of the chip.
It can be divided into three types: B, which does not go out of the chip, and C, whose output is connected to the outside of the chip. 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 embodiment of a circuit configuration in which the present invention is applied to the logic circuit A in _{FIG .} One constant current source Q ₁₁ , R ₁₁ has a control terminal 12 led out, and the other constant current source Q ₁₀ , R ₁₀ is connected to a constant voltage that provides a constant current source reference voltage in the chip. It has a terminal 11. Since transistor _Q11 is in a cutoff state unless a constant voltage (control signal) is applied to control terminal 12, the circuit of FIG. 4 operates in the same way as the logic circuit of FIG. 1. i.e. transistor Q ₈
The reference voltage connected to the base of is set at the center of the logic swing of the logic circuit of FIG. 1 and provides a reference for small logic swings.

The logic input voltage applied to input terminal 9 or 10 is increased (e.g. the transistor in Fig. 4).
(twice the logic amplitude at the collectors of Q ₆ , Q ₇ , and Q ₈ ), the reference voltage of the logic circuit (base potential of transistor Q ₈ ) will shift toward the logic “1” side. That is, 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 _Q11 also becomes conductive, and twice the current flows through the resistor _R8 that generates the reference voltage, so the reference voltage becomes twice as high as the input voltage. The reference voltage is set at the center of the twice the logic amplitude added to , 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 2
I thought about double the input logic amplitude, but the input logic amplitude is 2
It is clear that any reference voltage can be generated by changing the value of the resistor R ₁₁ in order to generate a reference voltage that does not need to be doubled and is responsive to the input logic amplitude. Furthermore, if it is not desired to change the value of the resistor _R11 , the same effect can be obtained by changing the constant voltage applied to the control terminal 12.

That is, it can be seen that the circuit shown in FIG. 4 enables logical 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, two constant current sources Q ₁₅ , R ₁₅ , Q ₁₆ ,
It is configured with R ₁₆ . one constant current source
Q ₁₅ and R ₁₅ have control terminals 17, and other constant current sources
Constant current source reference voltage terminals 18 of R ₁₆ and R ₁₆ are supplied with a constant voltage within the chip. Control terminal 17
When no constant voltage (control signal) is applied to the logic circuit of FIG. 5, the logic circuit of FIG. ₅ operates at the same logic level as the logic circuit of FIG. If the resistance value of _R16 is taken to be equal to the resistance value of resistor R16, twice as much current will flow through the current switching circuit compared to the previous state, and therefore output terminal 1
The logic amplitude appearing at 5 or 16 is also doubled. In this explanation, a constant current circuit consisting of a transistor Q ₁₅ and a resistor R ₁₅ is considered to have the same characteristics as a constant current source consisting of a transistor Q ₁ and a resistor R ₁ . The ability to change the amplitude arbitrarily is the same 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 amplitudes 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 resistor R ₈ from which the reference voltage is obtained, or the load resistor R ₁₂ ,
The current flowing through _R13 is controlled to be activated or deactivated using a voltage control signal sent to the control terminal of the constant current source, and the reference voltage can be increased in accordance with the logic amplitude of an external logic circuit connected to this chip, or You can increase the level.

Therefore, logic circuits can be operated at low power and high speed inside an LSI chip, and the logic circuits can be operated with a very small amplitude signal without using an extra level conversion chip, and with a large logic amplitude outside the chip. I can do it. As a result, packaging density is increased, and since no extra level conversion chips are used, costs can be reduced. Furthermore, by manufacturing the LSI chip according to the present invention, for example, multi-chip LSI
(For example, when multiple chips are mounted on an alumina substrate interconnected to form an LSI), when you want to operate with a small logic amplitude inside the alumina substrate and operate with a large logic amplitude outside the alumina substrate. However, since the purpose of the chip connected to the terminals of the alumina substrate can be easily achieved by shorting the control terminal and the constant current source reference constant voltage terminal, it is necessary to manufacture LSI chips with different logic amplitudes. The economic effect is large.

In the above description, the operation of the present invention was mainly explained using an LSI chip using NPN transistors, but the present invention can also be applied to an LSI chip using PNP transistors. Furthermore, the present invention can be applied only to either the input logic circuit or the output logic circuit of an LSI chip.

[Brief explanation of the drawing]

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

Claims (1)

[Claims] 1. A pair of current switching transistors receiving an input signal and a reference signal, a load circuit connected between one end of each of the pair of transistors and a first power source, and the other end of the pair of transistors connected in common. and a first and second constant current circuit connected in parallel between the connection point and a second power supply, and means for taking out an output from the one end of the transistor pair, on the same semiconductor substrate. The first constant current circuit always operates in response to an internal signal generated on the semiconductor substrate, and the second constant current circuit responds to a signal input from outside the semiconductor substrate. A semiconductor logic circuit characterized in that it is controlled to operate when the amplitude level of an output taken out from the one end of the transistor pair is made to be different from a normal level.