JPH05199096A - Semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To output directly a signal to the semiconductor integrated circuit whose power supply voltage differs and the circuit the threshold level of input signal and output signal of which differs by devising the circuit such that a highest level and a minimum level of the output signal are revised optionally. CONSTITUTION:A digital signal 15 outputted from an internal circuit 13 is converted into an analog signal 16 by a D/A converter 14 and the analog signal 16 is used for a power supply of an output circuit 11. Then a voltage of a signal outputted at an output terminal 12 is set to an optional value by the digital signal 15. Thus, a signal coincident with the voltage is directly inputted to the semiconductor integrated circuit whose power supply voltage differs from each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit, and more particularly to an output circuit in a semiconductor integrated circuit.

[0002]

2. Description of the Related Art As a conventional semiconductor integrated circuit, there is a circuit shown in FIG. As shown in FIG. 4, the output circuit 41 in the conventional semiconductor integrated circuit is shared with the internal circuit 43, and the level of the output signal output to the output terminal 42 is limited by the power supply voltage. The minimum level cannot be changed.

Therefore, when a device is constructed by using a plurality of semiconductor integrated circuits, it is impossible to directly electrically connect the semiconductor integrated circuits having different power supply voltages. When electrically connecting semiconductor integrated circuits having different power supply voltages, an interface for changing the maximum level or the minimum level of the output signal is required between the connection parts.

FIG. 5 is a block diagram showing an example of a plurality of conventional semiconductor integrated circuits in which semiconductor integrated circuits having different power supply voltages are electrically connected. The conventional semiconductor integrated circuit 51 has a power supply voltage of 5V, and the conventional semiconductor integrated circuit 52 has a power supply voltage of 3V. Semiconductor integrated circuit 5
A signal having a maximum level of about 5 V output from the unit 1 cannot be directly input to the semiconductor integrated circuit 52. Therefore, an interface 53 for converting the maximum level of the input signal from 5V to 3V is provided between the semiconductor integrated circuit 51 and the semiconductor integrated circuit 52.

[0005]

However, in the above-mentioned conventional semiconductor integrated circuit, since the maximum level and the minimum level of the output signal cannot be changed, the thresholds of the semiconductor integrated circuit and the input / output signals having different power supply voltages are not able to be changed. There is a problem that a signal cannot be directly output to a circuit having a different value and an interface is required.

The present invention has been made in view of the above problems, and by making it possible to arbitrarily change the maximum level and the minimum level of an output signal in a semiconductor integrated circuit, semiconductors having different power supply voltages can be obtained. An object of the present invention is to provide a semiconductor integrated circuit capable of directly outputting a signal to the integrated circuit and a circuit having different input / output signal threshold values.

[0007]

A semiconductor integrated circuit according to the present invention is a semiconductor integrated circuit having an output circuit in which a maximum value or a minimum value of an output voltage changes in accordance with a power supply voltage. It is characterized by having a D / A converter that outputs an analog voltage.

[0008]

In the semiconductor integrated circuit according to the present invention, in the semiconductor integrated circuit having the output circuit in which the maximum value or the minimum value of the output voltage changes according to the power supply voltage, the D / A conversion for supplying the power of the output circuit. The power supply voltage of the output circuit can be changed by the controller. As a result, the semiconductor integrated circuit according to the present invention can change the maximum level and the minimum level of the output signal to an arbitrary level, so that the semiconductor integrated circuit having a different power supply voltage and the circuit having a different threshold value of the signal can be directly connected. A signal can be input.

[0009]

Embodiments of the present invention will now be described with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a semiconductor integrated circuit according to a first embodiment of the present invention. As shown in FIG. 1, the output circuit 11 uses the analog output 16 of the D / A converter 14 as a power source and outputs the signal input from the internal circuit 13 to the output terminal 12. The D / A converter 14 has an internal circuit 1
The digital signal 15 inputted from 3 is converted into an analog voltage and supplied as an analog output 16 and as a power source for the output circuit 11. The internal circuit 13 sets the value of the digital signal 15 and outputs it to the D / A converter 14.

Next, the operation of the semiconductor integrated circuit according to this embodiment configured as described above will be described. Output circuit 1
Since the power source of No. 1 is the analog output 16 of the D / A converter 14, the maximum level of the output voltage of the output circuit 11 is changed by changing the digital signal 15 output by the internal circuit 13 to an arbitrary digital value. The voltage is changed to the voltage corresponding to the value of the digital signal 15. Therefore, in the semiconductor integrated circuit according to the present embodiment, the maximum level in the output voltage is D / A.
It can be changed to an arbitrary voltage via the converter 14.

FIG. 2 is a block diagram showing a circuit electrically connected to semiconductor integrated circuits having different power supply voltages using the semiconductor integrated circuit according to the second embodiment of the present invention. As shown in FIG. 2, the semiconductor integrated circuit 29 according to this embodiment includes output circuits 21, 22, 23, 24, a D / A converter 25, and an internal circuit 26. The analog output 27 of the D / A converter 25 serves as a power source for the output circuits 21, 22, 23 and 24. The analog output 27 of the D / A converter 25 can be changed to an arbitrary voltage by the digital signal 28 input from the internal circuit 26.

The power supply voltage of the semiconductor integrated circuit 29 is 5V, and the power supply voltage of the semiconductor integrated circuit 30 is 3V. In the case of a conventional semiconductor integrated circuit, the maximum output voltage level of a semiconductor integrated circuit with a power supply voltage of 5V is about 5V,
It is not possible to directly output a signal from a semiconductor integrated circuit having a power supply voltage of 5V to a semiconductor integrated circuit having a power supply voltage of 3V. However, in the semiconductor integrated circuit 29 according to the present embodiment, by setting the voltage of the analog output 27 of the D / A converter 25 to 3V by the digital signal 28 input from the internal circuit 26, the output circuits 21, 22, and 23 are output. , 24, the maximum level at the output voltage can be about 3V. Therefore, the semiconductor integrated circuit 29 according to the present embodiment can directly output a signal to another semiconductor integrated circuit 30 having a different power supply voltage.

FIG. 3 is a block diagram showing a circuit electrically connected to a plurality of semiconductor integrated circuits having different power supply voltages using the semiconductor integrated circuit according to the first embodiment of the present invention.
As shown in FIG. 3, the semiconductor integrated circuit 36 according to the present embodiment.
The output circuit 31 in FIG.
It is connected to each input circuit of 39. Semiconductor integrated circuit 3
The power supply voltage of 6 is 5V, the power supply voltage of the semiconductor integrated circuit 37 is also 5V, and the power supply voltage of the semiconductor integrated circuit 38 is 3V.
V, and the power supply voltage of the semiconductor integrated circuit 39 is 1.5V.

The semiconductor integrated circuit 36 is the semiconductor integrated circuit 3
In the case of outputting a signal to 7, the D / A converter 32 uses the digital signal 35 input from the internal circuit 33 to generate 5V.
Of the analog output 34, and the maximum level of the output voltage of the output circuit 31 is set to about 5V. Similarly, when the semiconductor integrated circuit 36 outputs a signal to the semiconductor integrated circuit 38, the semiconductor integrated circuit 36 sets the maximum level in the output voltage of the output circuit 31 to about 3 V, and when outputting a signal to the semiconductor integrated circuit 39, The maximum level of the output voltage of the output circuit 31 is set to about 1.5V.

As described above, the semiconductor integrated circuit 36 according to this embodiment can set the maximum level of the output voltage of the output circuit 31 to an arbitrary value by the digital signal 35 output from the internal circuit 33. Therefore, the semiconductor integrated circuit according to the present embodiment can output a signal at a voltage level that matches the power supply voltage of the output destination and the threshold value of the signal even when the signal is output to the semiconductor integrated circuits having different power supply voltages. Therefore, it is possible to directly output the signal without passing through another interface circuit. Further, the semiconductor integrated circuit according to the present embodiment can easily make the voltage level of the output signal correspond to the output destination semiconductor integrated circuit even when the power supply voltage of the output destination semiconductor integrated circuit is changed. ..

In the above embodiment, only the highest level in the output voltage is variable, but by using the analog output of the D / A converter as the low level power supply in the output circuit, the lowest level in the output voltage can be maintained. It can be variable.

[0018]

As described above, according to the semiconductor integrated circuit of the present invention, since the maximum level and the minimum level of the output signal in the semiconductor integrated circuit can be changed to arbitrary levels, semiconductors having different power supply voltages can be changed. A signal can be directly input to an integrated circuit and a circuit having different signal threshold values. Therefore, when a device is configured using a plurality of semiconductor integrated circuits, the device can be configured without using other interface circuits even if the semiconductor integrated circuits having different power supply voltages are included.

[Brief description of drawings]

FIG. 1 is a block diagram showing a semiconductor integrated circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a circuit electrically connected to semiconductor integrated circuits having different power supply voltages using the semiconductor integrated circuit according to the second embodiment of the present invention.

FIG. 3 is a block diagram showing a circuit electrically connected to a plurality of semiconductor integrated circuits having different power supply voltages using the semiconductor integrated circuit according to the first exemplary embodiment of the present invention.

FIG. 4 is a block diagram showing an example of a conventional semiconductor integrated circuit.

FIG. 5 is a block diagram showing an example of a circuit in which semiconductor integrated circuits having different power supply voltages are electrically connected in a plurality of conventional semiconductor integrated circuits.

[Explanation of symbols]

11, 21, 22, 23, 24, 31, 41; Output circuit 13, 26, 33, 43; Internal circuit 14, 25, 32; D / A converter

Claims (2)

[Claims] 1. A semiconductor integrated circuit having an output circuit in which a maximum value or a minimum value of an output voltage changes in accordance with a power supply voltage, the semiconductor integrated circuit having a D / A converter which outputs an analog voltage as a power supply of the output circuit. A semiconductor integrated circuit characterized by the above. 2. The semiconductor integrated circuit according to claim 1, further comprising a control unit that outputs a predetermined digital value to the D / A converter.