JP3530315B2 - Output circuit - Google Patents

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 (LSI) composed of MOS transistors, and in particular, it is connected to another LSI having a power supply voltage higher than the gate oxide film breakdown voltage of the MOS transistor. The present invention relates to an output circuit that serves as an interface for.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of semiconductor integrated circuits,
The withstand voltage of semiconductor devices, particularly the withstand voltage of the gate oxide film of MOS transistors, has decreased, and along with this, the number of LSIs using a low voltage of 3 V or less as a power supply voltage has increased. However, even if the power supply voltage of the LSI is 3V, the power supply voltage of the external LSI connected to this LSI is, for example, 5V.
In the case of V, an output circuit for converting the power supply voltage of 3V into 5V and outputting it is necessary.

A conventional output circuit will be described below with reference to the drawings. This output circuit is a circuit that sets the potential state of the output pad portion to any one of the power supply potential, the ground potential, and the high impedance of the external LSI.

FIG. 13 is a circuit diagram showing the structure of a conventional output circuit. In FIG. 13, OUT is an output pad section to which the signal line of the external LSI is connected, IN and EN are output control terminals for controlling the potential state of the output pad section OUT, and IN is a signal input from the on-chip circuit. EN is an enable terminal for inputting an enable signal. VDD1 is the first potential, and its value is L
The voltage is equal to or lower than the withstand voltage of the gate oxide film of the MOS transistor forming SI, and is, for example, 3V, VDD2 is the second potential which is the power supply potential of the external LSI, and its value is, for example, 5V.

Reference numeral 110 is a signal generation circuit for generating a pull-up control signal and a pull-down control signal according to the potentials of the output control terminals IN and EN, and NAND gates 11 and N.
It is composed of an OR gate 12. The NAND gate 11 and the NOR gate 12 are supplied with the first potential VDD1 as the power supply potential and operate at a voltage equal to or lower than the gate oxide film breakdown voltage of the MOS transistor.

Reference numeral 120 denotes a voltage conversion circuit for boosting and outputting the pull-up control signal input from the signal generation circuit 110. The voltage conversion circuit 120 has P-type MOS transistors 21, 22 and N-type MO.
It is composed of S transistors 23 and 24, and an inverter circuit 29 for inverting the logic of signals. P type M
The second potential V is applied to the sources of the OS transistors 21 and 22.
DD2 is applied, the drains of the P-type MOS transistor 21 and the N-type MOS transistor 23 are connected to each other,
The drains of the P-type MOS transistor 22 and the N-type MOS transistor 24 are connected to each other, and the sources of the N-type MOS transistors 23 and 24 are grounded.

The pull-up control signal input from the signal generating circuit 110 is input to the gate of the N-type MOS transistor 23, and the pull-up control signal is inverted and input to the N-type MOS transistor 24 by the inverter circuit 29. It The gate of the P-type MOS transistor 21 is connected to the drain of the P-type MOS transistor 22 (drain of the N-type MOS transistor 24) (node B), P
The gate of the type MOS transistor 22 is connected to the drain of the P type MOS transistor 21 (the drain of the N type MOS transistor 23) (node A). From node B,
The boosted pull-up control signal is output. Further, the inverter circuit 29 has a first potential VDD as a power source potential.
1 is given.

A pull-up circuit 130 is a P-type MO.
It is composed of an S transistor 31. P type MO
The gate of the S transistor 31 is connected to the node B of the voltage conversion circuit 120, and the source and the substrate have the second potential VDD.
2 is applied, the drain is connected to the output pad section OUT, and the potential of the output pad section OUT is raised to the second potential VDD2 when in the ON state.

A pull-down circuit 140 is an N-type MO.
It is composed of an S transistor 41. N type MO
The output signal of the NOR gate 12 of the signal generation circuit 110 is applied to the gate of the S-transistor 41, the source and the substrate are grounded, and the drain is connected to the output pad section OUT. Pull the potential down to ground potential.

The operation of the conventional output circuit shown in FIG. 13 configured as above will be described with reference to FIGS. 14 and 15. In the following description, a high level (high potential) in a digital signal is ““ H ”” and a low level (low potential) is “L”. The value of the electric potential is also attached. Further, here, the first potential VDD1 is set to 3V and the second potential VDD2 is set to 5V.

First, "H" (5
The operation of outputting V) will be described with reference to FIG.
In this case, an “H” (3V) enable signal is input to the enable terminal EN and an “H” (3V) signal is input to the input terminal IN.
Input the input signal V).

Then, the output signal of the NAND gate 11 becomes "L" (0V), and the output signal of the NOR gate 12 also becomes "L" (0V). When the output signal of the NAND gate 11 becomes 0V, the gate potential of the N-type MOS transistor 23 becomes 0V, while the gate of the N-type MOS transistor 24 becomes the NAND gate 1 through the inverter circuit 29.
Since it is connected to 1, its potential will be 3V. Therefore, the N-type MOS transistor 23 is turned off and the N-type MOS transistor 24 is turned on. When the N-type MOS transistor 24 is turned on, the potential of the node B is lowered, so that the P-type MOS transistor 21 is turned on because the gate potential is lowered. Since the P-type MOS transistor 21 is turned on and the N-type MOS transistor 23 is turned off, the potential of the node A becomes 5V. When the potential of the node A becomes 5V, the P-type MOS transistor 22 is turned off, while the N-type MOS transistor 24 is turned on, so that the potential of the node B becomes 0V.

When the potential of the node B becomes 0 V, the P-type MOS
The transistor 31 is turned on because the gate potential becomes 0V, and the N-type MOS transistor 41 is turned off because the gate potential becomes 0V because the output signal of the NOR gate 12 is 0V. The P-type MOS transistor 31 is on and the N-type MOS transistor 41 is off, and the source of the P-type MOS transistor 31 has the second potential V
Since DD2 is applied, the potential of the output pad OUT becomes "H" (5V). As described above, when an “H” (3V) enable signal is input to the enable terminal EN and an “H” (3V) input signal is input to the input terminal IN, “H” (5V) is output from the output pad section OUT. Is output. In FIG. 14, “H” (5
The MOS transistor that is turned on when V) is output is surrounded by a dashed circle.

Next, from the output pad section OUT to "L" (0
The operation of outputting V) will be described with reference to FIG.
In this case, an “H” (3V) enable signal is input to the enable terminal EN and an “L” (0
Input the input signal V).

Then, the output signal of the NAND gate 11 becomes "H" (3V), and the output signal of the NOR gate 12 also becomes "H" (3V). When the output signal of the NAND gate 11 becomes 3V, the gate potential of the N-type MOS transistor 23 becomes 3V, while the N-type MOS transistor 2
Since the gate of No. 4 is connected to the NAND gate 11 via the inverter circuit 29, its potential becomes 0V. Therefore, the N-type MOS transistor 23 is turned on,
The N-type MOS transistor 24 is turned off. N-type MOS
When the transistor 23 is turned on, the potential of the node A is lowered, and therefore the P-type MOS transistor 22 is turned on because the gate potential is lowered. Since the P-type MOS transistor 22 is turned on and the N-type MOS transistor 24 is turned off, the potential of the node B becomes 5V. When the potential of the node B becomes 5V, the P-type MOS transistor 21 is turned off, while the N-type MOS transistor 23 is turned on, so that the potential of the node A becomes 0V.

The P-type MOS transistor 31 is off because the gate potential, that is, the potential of the node B is 5V, and the N-type MOS transistor 41 is on because the output signal of the NOR gate 12 is 3V and the gate potential is 3V. is there. When the P-type MOS transistor 31 is off and N
Type MOS transistor 41 is ON, and an N type M
Since the source of the OS transistor 41 is grounded,
The potential of the output pad section OUT becomes "L" (0V). In this manner, the enable signal EN is input with an enable signal of "H" (3V) and the input terminal IN is supplied with "L" (0V).
When the input signal V) is input, "L" (0V) is output from the output pad section OUT. In FIG. 15, a MOS transistor that is turned on when “L” (0 V) is output from the output pad section OUT is surrounded by a dashed circle.

Next, the operation for setting the output pad section OUT in the high impedance state will be described. in this case,
The enable signal input to the enable terminal EN is set to "L" regardless of the logical value of the signal input to the input terminal IN.

Then, the output signal of the NAND gate 11 becomes "H" (3V) and the output signal of the NOR gate 12 becomes "L" (0V). Since the output signal of the NAND gate 11 is 3V, the P-type MOS transistor 31 is operated by the same operation as when "L" is output from the output pad section OUT.
Turns off. Further, the output signal of the NOR gate 12 is 0
Since it is V, the N-type MOS transistor 41 is turned off by the same operation as in the case of outputting "H" from the output pad section OUT. Therefore, since both the P-type MOS transistor 31 and the N-type MOS transistor 41 are turned off, the output pad section OUT is in a high impedance state.

[0019]

However, the conventional output circuit has the following problems.

In the conventional output circuit as shown in FIG. 13,
Between the gate and drain of the MOS transistor or the gate
A potential difference between the second potential VDD2 and the ground potential, that is, a voltage equal to the power supply voltage of the external LSI is applied between the sources.
Since the gate-drain voltage or the gate-source voltage of the MOS transistor is applied to the gate oxide film due to its structure, the gate oxide film is destroyed or deteriorated when the power supply voltage of the external LSI is equal to or higher than the gate oxide film breakdown voltage.

For example, from the output pad section OUT to "H"
When outputting (5 V), the gate potential of the N-type MOS transistor 41 forming the pull-down circuit 140 is set to 0 V to turn it off, and the pull-up circuit 1
In order to turn on the P-type MOS transistor 31 forming the transistor 30, the gate potential thereof is set to 0V. At this time,
Since the gate potential of the N-type MOS transistor 41 becomes 0V and the potential of the drain connected to the output pad portion OUT becomes 5V, the gate-drain voltage becomes 5V. Similarly, the P-type MOS transistor 31 has a gate
The source-to-source voltage becomes 5V. Therefore, a voltage (5 V) higher than the breakdown voltage is applied to the gate oxide films of the N-type MOS transistor 41 and the P-type MOS transistor 31.

At this time, a voltage higher than the withstand voltage is also applied to the gate oxide film of each MOS transistor constituting the voltage conversion circuit 120. For example, N-type MOS transistor 23
, The potential of the drain connected to the node A becomes 5V and the gate-drain voltage becomes 5V. In addition, the P-type MOS transistor 22
, The potential of the gate connected to the node A becomes 5V and the potential of the drain connected to the node B becomes 0V, so that the gate-drain voltage becomes 5V. Furthermore, P
Type MOS transistor 21 has a second potential VD at its source.
Since 5V is applied as D2 and the potential of the gate connected to the node B becomes 0V, the gate-source voltage becomes 5V.

When "L" is output from the output pad section OUT, the potential of the node B becomes 5V and the potential of the output pad section OUT becomes 0V. Therefore, the potential between the gate and drain of the P-type MOS transistor 31 is increased. The voltage becomes 5V.
Also in the voltage conversion circuit 120, the N-type MOS transistor 24 has a gate potential of 0 V and a node B.
Since the potential of the drain connected to
The drain-to-drain voltage becomes 5V. The potential of the gate of the P-type MOS transistor 21 connected to the node B is 5V.
And the potential of the drain connected to node A becomes 0V
Therefore, the gate-drain voltage becomes 5V. Further, in the P-type MOS transistor 22, 5V is applied to the source as the second potential VDD2 and the potential of the gate connected to the node A becomes 0V, so that the gate-source voltage becomes 5V.

Further, even when the output pad portion OUT is set to the high impedance state, the gate potential of the P-type MOS transistor 31 becomes 5V, so that the output pad portion OU
When 0V is applied to T, the gate-drain voltage of the P-type MOS transistor 31 becomes 5V. In addition, N-type MOS
Since the gate potential of the transistor 41 becomes 0V, if 5V is applied to the output pad portion OUT, the gate-drain voltage of the N-type MOS transistor 41 becomes 5V.

As described above, in the conventional output circuit, the power supply voltage of the external LSI connected to the conventional output circuit constitutes the MO that constitutes this output circuit.
When the gate oxide film withstand voltage of the S transistor is higher than the withstand voltage, a voltage higher than the withstand voltage is applied to the gate oxide film of each MOS transistor, and the gate oxide film is broken or deteriorated. This problem can be avoided by using a MOS transistor having a large gate oxide film breakdown voltage.
Increasing the breakdown voltage of the gate oxide film of the S transistor is not preferable because it hinders miniaturization of the semiconductor integrated circuit.

In view of the above problems, the present invention provides an external LSI
In the output circuit serving as an interface for connecting with the external LSI, even if the power supply voltage of the external LSI is equal to or higher than the gate oxide film breakdown voltage of the MOS transistor forming the output circuit, a voltage higher than the breakdown voltage is applied to the gate oxide film of each MOS transistor It is an object of the present invention to enable output of a signal whose amplitude is the power supply voltage of the external LSI.

[0027]

[Means for Solving the Problems ]
Therefore, the means taken by the invention of claim 1 is that the first potential is a power source.
The output signal of one circuit, which is the potential, is input, and this
The second potential from the output according to the output signal of the path
Input as an output circuit that outputs a signal to another circuit
Based on the output signal of the one circuit
The first and second amplitudes are the potential difference between the potential and the ground potential.
A signal generating circuit for generating a control signal, and the signal generating circuit
The first control signal generated by
Pull-up control by converting the amplitude of the control signal of 1
A voltage conversion circuit that generates and outputs a control signal, and the voltage conversion circuit
With the pull-up control signal output from the conversion circuit as input,
According to the instruction of this pull-up control signal,
Pull for controlling whether or not the position is raised to the second potential
Up circuit and a first circuit generated by the signal generating circuit.
Input the control signal of 2 as a pull-down control signal.
The potential of the output section is changed according to the pull-down control signal instruction.
Pull-down circuit that controls whether or not it is pulled down to ground potential
And the pull-up circuit has a source connected to the second
A potential is applied and the pull-up control signal is applied to the gate.
An input first P-type MOS transistor, and the first
The source is connected to the drain of the P-type MOS transistor of
And the drain is connected to the output and the gate
A second electric potential to which a third electric potential different from the first electric potential is applied to
And a P-type MOS transistor of
The source is grounded and the gate has the pull-down control.
A first N-type MOS transistor to which a control signal is input,
Source to the drain of the first N-type MOS transistor
And the drain is connected to the output section and
Second N-type MO having the first potential applied to its gate
An S-transistor, the voltage conversion circuit
The pulling to raise the electric potential of the force section to the second electric potential.
When instructing the up circuit, the pull-up control signal
From the second potential to the first P-type MOS transistor.
The potential is less than or equal to the potential obtained by subtracting the threshold voltage of the transistor, and the second
From the potential of the gate of the first P-type MOS transistor
A voltage that is equal to or higher than the potential obtained by subtracting the oxide film breakdown voltage.
On the other hand, the electric potential of the output section is raised to the second electric potential.
If you do not instruct the pull-up circuit,
The potential of the control signal is set to the second potential.
It

Further, the output circuit according to the invention of claim 1 is
Road includes a first detecting a potential difference between said second potential potential, the potential difference detection circuit, wherein the second potential is outputted a potential difference detection signal indicating whether or not greater than the first potential When a predetermined potential and a ground potential are applied and the potential difference detection signal output from the potential difference detection circuit is input, and the potential difference detection signal indicates that the second potential is larger than the first potential, A switch circuit that selectively outputs the predetermined potential, and selectively outputs a ground potential when the potential difference detection signal indicates that the second potential is less than or equal to the first potential, Monodea to the output potential of the circuit and the third potential
It

According to the first aspect of the invention, the predetermined potential is selected as the third potential by the potential difference detection circuit and the switch circuit when the second potential is higher than the first potential, while the second potential is selected. When the potential of is less than or equal to the first potential, the ground potential is selected as the third potential. For this reason,
Even if the second potential changes, the optimum potential is always selected as the third potential such that the gate oxide film of the MOS transistor does not receive a voltage higher than the withstand voltage and the drain current of the MOS transistor becomes large.

In the invention of claim 2 , the above-mentioned claim
The predetermined potential in the first output circuit is equal to or lower than the first potential and equal to or higher than the second potential minus the gate oxide film breakdown voltage equivalent voltage of the first P-type MOS transistor.

[0031] In the invention of claim 3, the potential difference detection circuit in the output circuit of claim 1, seventh P wherein the and gate the second potential is applied to the source a first potential is applied Type MOS transistor, and the first for the source
An eighth P-type MOS transistor to which a potential of
A seventh N-type MOS transistor whose drains are connected to each other and a seventh N-type MOS transistor whose drain is connected to the source of the seventh N-type MOS transistor and whose source is grounded. A MOS transistor, a ninth N-type MOS transistor in which the drain is connected to the eighth P-type MOS transistor and the source is grounded, and the first potential is applied to the drain and the second potential is applied to the gate. A tenth N-type MOS transistor to which a potential is applied and whose source is connected to the gate of the eighth P-type MOS transistor;
N-type MOS transistor gate and the ninth N-type M
The drain of the OS transistor is connected to the gate of the ninth N-type MOS transistor and the eighth N-type MOS transistor.
The drain of the type MOS transistor is connected, and the potential difference detection signal is output from a node where the drains of the eighth P-type MOS transistor and the ninth N-type MOS transistor are connected to each other.

In the invention of claim 4 , the above-mentioned claim
In the third output circuit, the seventh and eighth P-type MOS
The substrate potential of the transistor is the second potential, and the substrate potentials of the seventh, eighth, ninth and tenth N-type MOS transistors are ground potentials.

Further, the solution means taken by the invention of claim 5
Is the output signal of the one circuit in which the first potential is the power supply potential.
As an input, from the output section according to the output signal of this one circuit
Output a signal to another circuit that uses the second potential as the power supply potential
As an output circuit, the input output signal of the one circuit is
The amplitude of the potential difference between the first potential and the ground potential is based on
Signal generation circuit for generating first and second control signals
And a first control signal generated by the signal generating circuit.
Signal as an input, and the amplitude of this first control signal can be converted.
Generates a pull-up control signal by
Conversion circuit and pull-up output from the voltage conversion circuit
Use the control signal as an input and specify the pull-up control signal.
Therefore, the potential of the output section is raised to the second potential.
Pull-up circuit for controlling whether or not the signal generation circuit
The second control signal generated by the pull-down control signal.
Signal and follow the instructions of this pull-down control signal.
Control whether or not the potential of the output section is lowered to the ground potential.
And a pull-down circuit for controlling the pull-up circuit.
Is applied with the second potential at the source and before the gate.
The first P-type MOS transistor to which the pull-up control signal is input
The transistor and the transistor of the first P-type MOS transistor.
The source is connected to the rain and the drain is the output
A third gate connected to the gate and different from the first potential at the gate
And a second P-type MOS transistor to which the potential of
The pull-down circuit has a source grounded and a gate.
First N-type to which the pull-down control signal is input
MOS transistor and the first N-type MOS transistor
The source is connected to the drain of the
It is connected to the output section and the gate is imprinted with the first potential.
An added second N-type MOS transistor,
The voltage conversion circuit changes the potential of the output section to the second potential.
When instructing the pull-up circuit to pull up,
The potential of the pull-up control signal is changed from the second potential
Subtracting the threshold voltage of the first P-type MOS transistor
Below the potential and from the second potential to the first P-type MO
S-transistor gate oxide film withstand voltage equivalent voltage subtracted
While the potential of the output section is set to the second or higher,
Do not instruct the pull-up circuit to raise the potential of
If not, the potential of the pull-up control signal is set to the second
It is to be a potential.

Further, the output circuit according to the invention of claim 5 is
Road includes a first detecting a potential difference between said second potential potential, the potential difference detection circuit, wherein the second potential is outputted a potential difference detection signal indicating whether or not greater than the first potential When the potential difference detection signal output from the potential difference detection circuit is input and the potential difference detection signal indicates that the second potential is larger than the first potential, the operating speed of the voltage conversion circuit is promoted. Meanwhile, when the potential difference detection signal indicates that said second potential is equal to or less than the first potential are those provided with a voltage conversion accelerator circuit does not promote the operating speed of said voltage conversion circuit.

According to the invention of claim 6 , the above-mentioned claim
In the output circuit of No. 5, the voltage conversion circuit includes third and fourth P-type MOS transistors whose sources are supplied with the second potential.
A transistor, a fifth P-type MOS transistor whose source is connected to the drain of the third P-type MOS transistor, and a sixth P-type MOS transistor whose source is connected to the drain of the fourth P-type MOS transistor. A transistor, a third N-type MOS transistor whose drain is connected to the sixth P-type MOS transistor, and a fourth source whose drain is connected to the source of the third N-type MOS transistor and whose source is grounded. The N-type MOS transistor, the fifth P-type MOS transistor and the fifth N-type MOS transistor whose drains are connected to each other, and the drain of which is connected to the source of the fifth N-type MOS transistor and the source of which is grounded. A sixth N-type MOS transistor, and a gate of the third P-type MOS transistor and the third N-type MOS transistor. Is connected to the drain of the P-type MOS transistor, and the gate of the fourth P-type MOS transistor is connected to the drain of the third P-type MOS transistor, and the fifth and sixth P-type MOS transistors are connected. The third potential is applied to the gate of the second N-type MOS transistor, the first potential is applied to the gates of the third and fifth N-type MOS transistors, and the signal generation is applied to the gate of the sixth N-type MOS transistor. A first control signal generated by a circuit is input, an inverted signal of the first control signal is input to the gate of the fourth N-type MOS transistor, and a drain of the fourth P-type MOS transistor is input. The pull-up control signal is output from a node connected to the source of the sixth P-type MOS transistor. And, the voltage conversion promoting circuit,
An eleventh N-type MOS transistor having drains connected to the third P-type MOS transistor;
A twelfth N-type MOS transistor having a drain connected to the source of the first N-type MOS transistor and a source connected to the drain of the sixth N-type MOS transistor, and the fourth P-type MOS transistor and the drain Connected to a thirteenth N-type MOS transistor, and a fourteenth N-type MOS transistor whose drain is connected to the source of the thirteenth N-type MOS transistor and whose source is connected to the drain of the fourth N-type MOS transistor. A MOS transistor, wherein the first potential is applied to the gates of the eleventh and thirteenth N-type MOS transistors, and the potential difference detection signal is input to the gates of the twelfth and fourteenth N-type MOS transistors. I shall. Further, the potential difference detection circuit outputs the first potential as the potential difference detection signal when the second potential is larger than the first potential, while the second potential is the first potential. In the following cases, the ground potential is output as the potential difference detection signal.

Further, in the invention of claim 7 , the above-mentioned claim
It is assumed that the source of the twelfth N-type MOS transistor in the sixth output circuit receives the inverted signal of the first control signal instead of being connected to the drain of the sixth N-type MOS transistor.

In the invention of claim 8 , the above-mentioned claim
It is assumed that the source of the 14th N-type MOS transistor in the output circuit of 7 receives the first control signal instead of being connected to the drain of the fourth N-type MOS transistor.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

( First Reference Example ) FIG. 1 is a circuit diagram showing a configuration of an output circuit according to a first reference example of the present invention. The output circuit according to the present invention is used as an interface with an external LSI having a power supply voltage equal to or higher than a gate oxide film breakdown voltage of a MOS transistor constituting the LSI, and an output pad according to an output signal of an internal circuit of the LSI. The potential state of the part is set to any one of the power supply potential (“H” level), the ground potential (“L” level) and high impedance of the external LSI.

In FIG. 1, OUT is an output pad section as an output section connected to the signal line of the external LSI, IN and EN are output control terminals for controlling the potential state of the output pad section OUT, and IN is ON. An input terminal for inputting a signal from a chip circuit (an internal circuit of the LSI), EN is an enable terminal for inputting an enable signal, and 10 is a first control signal S ₁ and a second control signal S ₁ according to the potentials of the output control terminals IN and EN.
, A voltage conversion circuit for generating the control signal S ₂ of the signal, a voltage conversion circuit 20 for boosting the first control signal S ₁ input from the signal generation circuit 10 and outputting the boosted control signal S _u , and a voltage conversion circuit 30. A pull-up circuit that raises the potential of the output pad section OUT according to the pull-up control signal S _u input from the circuit 20, and 40 indicates a second control signal S ₂ (pull-down control signal S _d ) input from the signal generation circuit 10. It is a pull-down circuit that lowers the potential of the output pad section OUT. Further, VDD1 is a first potential, the value of which is less than or equal to the breakdown voltage of the gate oxide film of the MOS transistor forming the LSI, for example, 3V, VDD2 is the second potential which is the power supply potential of the external LSI, and its value Is equal to or higher than the breakdown voltage of the gate oxide film of the MOS transistor forming the LSI and is, for example, 5V.

The signal generation circuit 10 is composed of a NAND gate 11 and a NOR gate 12, which receive the signal input to the input terminal IN and the enable signal input to the enable terminal EN, respectively. While the control signal S _{1 of 1} is output, N
The OR gate 12 outputs the second control signal S ₂ .
Further, the NAND gate 11 and the NOR gate 12 are the first
Potential VDD1 is supplied as a power supply potential, and the MOS transistor operates at a voltage equal to or lower than the gate oxide film breakdown voltage of the MOS transistor.

The voltage conversion circuit 20 is composed of P-type MOS transistors 21, 22, 25, 26, N-type MOS transistors 23, 24, 27, 28, and an inverter circuit 29 for inverting the logic of signals. Compared with the voltage conversion circuit 120 in the conventional output circuit shown in FIG. 13, the P-type MOS transistors 21 and 22 and the N-type MO are provided.
P-type MOS transistors 25, 26 and N-type MOS transistors 27, 28 between the S transistors 23, 24
Has been inserted .

The sources of the P-type MOS transistors 21 and 22 are supplied with the second potential VDD2, and the drains thereof are connected to the sources of the P-type MOS transistors 25 and 26, respectively. Then, the P-type MOS transistor 2
The drains of 5, 26 are N-type MOS transistors 27, 2
8 and the sources of the N-type MOS transistors 27 and 28 are connected to the drains of the N-type MOS transistors 23 and 24, respectively.
The sources of the MOS transistors 23 and 24 are grounded.

The gate of the P-type MOS transistor 21 is P
Connected to the drain of the P-type MOS transistor 22 (source of the P-type MOS transistor 26) (node B),
The gate of the OS transistor 22 is connected to the drain of the P-type MOS transistor 21 (source of the P-type MOS transistor 25) (node A). The pull-up control signal S _u is output from the node B. The first potential VDD1 is applied to the gates of the P-type MOS transistors 25 and 26 and the N-type MOS transistors 27 and 28. Also, N
Signal generation circuit 1 at the gate of the MOS transistor 23.
The first control signal S ₁ generated by 0 is input,
The first control signal S ₁ is inverted by the inverter circuit 29 and input to the gate of the N-type MOS transistor 24.

P-type MOS transistors 21, 22, 2
The substrate potentials of 5 and 26 are the second potential VDD2, and the substrate potentials of the N-type MOS transistors 23, 24, 27 and 28 are ground potentials. Further, the inverter circuit 29 is supplied with the first potential VDD1 as a power supply potential.

The pull-up circuit 30 is a voltage conversion circuit 20.
The pull-up control signal Su output from the input pad OUT is input to raise the potential of the output pad portion OUT to the second potential VDD2 when "H" is output from the output pad portion OUT. It is composed by. Claim for the P-type MOS transistor 31
1 and 5 , corresponding to the first P-type MOS transistor, and the P-type MOS transistor 32 is the second P-type M transistor according to claim 1.
It corresponds to an OS transistor.

In the P-type MOS transistor 31, the pull-up control signal _Su is input to the gate, the second potential VDD2 is applied to the source, and the drain is connected to the source of the P-type MOS transistor 32. P-type MOS
In the transistor 32, the first potential VDD1 is applied to the gate, the source is connected to the drain of the P-type MOS transistor 31, and the drain is the output pad portion O.
It is connected to the UT. The substrate potentials of the P-type MOS transistors 31 and 32 are both the second potential VDD2.

The pull-down circuit 40 is a signal generation circuit 10.
When the pull-down control signal S _d (second control signal S ₂ ) output from the input pad is input and "L" is output from the output pad portion OUT, the potential of the output pad portion OUT is lowered to the ground potential. Type MOS transistor 41,
It is constituted by 42. N-type MOS transistor 41 corresponds to the first N-type MOS transistor according to claim 1, 5, N-type MOS transistor 42 corresponds to the second N-type MOS transistor according to claim 1, 5.

In the N-type MOS transistor 41, the pull-down control signal S _d is input to the gate, the source is grounded, and the drain is connected to the source of the N-type MOS transistor 42. The N-type MOS transistor 42 has a gate to which the first potential VDD1 is applied, a source connected to the drain of the N-type MOS transistor 41, and a drain connected to the output pad section OUT.

The operation of the output circuit according to this reference example shown in FIG. 1 will be described. In the following description, the first
Potential VDD1 of 3V and second potential VDD2 of 5V
And

First, "H" (5
The operation for outputting V) will be described with reference to FIG. In this case, an “H” (3V) enable signal is input to the enable terminal EN and an “H” (3V) signal is input to the input terminal IN.
Input the input signal V).

Then, the output signal of the NAND gate 11, that is, the first control signal S ₁ becomes "L" (0V), and N
The output signal of the OR gate 12, that is, the second control signal S ₂
Also becomes "L" (0V). The first control signal S ₁ is 0
Since it is V, the gate potential of the N-type MOS transistor 23 becomes 0V, and the gate potential of the N-type MOS transistor 24 becomes 3V because the first control signal S ₁ is input through the inverter circuit 29.

Therefore, the N-type MOS transistor 23
Turns off and the N-type MOS transistor 24 turns on. N
Type MOS transistor 28 has a gate potential of first potential V
It is on because it is DD1 or 3V, and it is a P-type M
The substrate potential of the OS transistor 26 is the second potential VDD2.
That is, it is 5 V and the gate potential is the first potential VDD.
Since it is 1 or 3 V, it is on. Therefore, N
Since the type MOS transistors 24 and 28 and the P-type MOS transistor 26 are all turned on, the potential at the node B is lowered, which turns on the P-type MOS transistor 21.

Since the P-type MOS transistor 21 is on and the N-type MOS transistor 23 is off, the node A
Potential of 5V. When the node A becomes 5V, the P-type MOS transistor 22 is turned off, while the N-type MOS transistors 24 and 28 and the P-type MOS transistor 26 are all on, so the potential of the node B is lowered. However, due to the presence of the P-type MOS transistor 26, the potential of the node B does not become 0V. At this time, the potential of the node B is VB, and the P-type MO considering the substrate bias effect
If the threshold voltage of the S transistor is VTP ', then VB = 3 + | VTP' |. That is, the potential of the pull-up control signal S _u becomes V (3+ | | VTP ') .

[0055] By the potential of the pull-up control signal S _u is lowered, P-type MOS transistor 31 of the pull-up circuit 30 is turned on. In addition, the P-type MOS transistor 3
2 is ON because the substrate potential is the second potential VDD2, that is, 5V, and the gate potential is the first potential VDD1, that is, 3V. Further, the N-type MOS transistor 41 of the pull-down circuit 40 has the pull-down control signal S _d (second control signal S ₂ ) output from the signal generation circuit 10.
Is 0V, the gate potential becomes 0V and the device is off. P
The type MOS transistor 31 is on, the N type MOS transistor 41 is off, and the source of the P type MOS transistor 31 is supplied with the second potential VDD2, that is, 5 V. Therefore, the potential of the output pad portion OUT is Becomes "H" (5V).

As described above, when the "H" (3V) enable signal is input to the enable terminal EN and the "H" (3V) input signal is input to the input terminal IN, "H" (H) is output from the output pad section OUT. "(5V) is output.
In FIG. 2, a MOS transistor that is turned on when “H” (5V) is output from the output pad section OUT is surrounded by a broken line.

At this time, the voltage of 5 V is not applied to the gate oxide film of any of the MOS transistors forming the output circuit, so that the gate oxide film is not destroyed or deteriorated.

That is, from the output pad section OUT to "H"
When outputting (5V), the N-type MOS transistor 23
Gate potential is 0V, while node A potential is 5V
However, due to the presence of the N-type MOS transistor 27 whose gate is supplied with the first potential VDD1, that is, 3V,
The drain potential VD23 of the N-type MOS transistor 23 does not become 5V and the N-type MOS transistor in consideration of the substrate bias effect.
If the threshold voltage of the transistor is VTN ', then VD23 = 3-VTN'. Therefore, the gate-drain voltage of the N-type MOS transistor 23 is (3-VTN ′) V, which is 5
It does not become V and is 3 V or less.

Further, since the potential of the node A becomes 5V and the potential of the node B becomes (3+ | VTP '|) V, the P-type MOS
The voltage between the gate and drain of the transistor 22 (VDG2
2), the absolute values of the gate-source voltage (VGS21) of the P-type MOS transistor 21 and the gate-source voltage (VGS31) of the P-type MOS transistor 31 are as follows: | VDG22 | = | VGS21 | = | VGS31 | = | (3+ | VTP '|) -5 | = 2- | VTP' |, which is 3V or less, not 5V.

Further, although the gate of the N-type MOS transistor 41 becomes 0V and the output pad portion OUT becomes 5V, the N-type MOS transistor 42 whose gate is supplied with the first potential VDD1, that is, 3V, has the N-type MOS transistor 42. M
The voltage applied to the drain of the OS transistor 41 (VD4
1) does not become 5V, but becomes VD41 = 3-VTN '. Therefore, also in the N-type MOS transistor 41, the gate-drain voltage is (3-VTN ') V, which is not 5V but 3V or less.

Next, from the output pad section OUT to "L" (0
The operation for outputting V) will be described with reference to FIG. In this case, an “H” (3V) enable signal is input to the enable terminal EN and an “L” (0
Input the input signal V).

Then, the output signal of the NAND gate 11, that is, the first control signal S ₁ becomes "H" (3V), and N
The output signal of the OR gate 12, that is, the second control signal S ₂
Also becomes "H" (3V). The first control signal S ₁ is 3
When it becomes V, the gate potential of the N-type MOS transistor 23 becomes 3V, and the gate potential of the N-type MOS transistor 24 becomes 0V because the first control signal S ₁ is inputted through the inverter circuit 29.

Therefore, the N-type MOS transistor 23
Turns on and the N-type MOS transistor 24 turns off. The N-type MOS transistor 27 is ON because the gate potential is the first potential VDD1, that is, 3V, and the P-type MOS transistor 25 is the substrate potential is the second potential VDD2, that is, 5V, and the gate potential is the first potential. Since the potential VDD1 is 3V, it is ON. Therefore, since the N-type MOS transistors 23 and 27 and the P-type MOS transistor 25 are all turned on, the node A
Potential of the P-type MOS transistor 2 decreases
2 turns on. Since the P-type MOS transistor 22 is turned on and the N-type MOS transistor 24 is turned off, the potential of the node B becomes 5V. That is, the potential of the pull-up control signal S _u becomes to 5V.

When the potential of the node B becomes 5V, P
Type MOS transistor 21 is turned off while N type MO
Since the S transistors 23 and 27 and the P-type MOS transistor 25 are all turned on, the potential at the node A drops,
Due to the presence of the P-type MOS transistor 25, it does not become 0V. At this time, the potential of the node A is VA, and the threshold voltage of the P-type MOS transistor considering the substrate bias effect is VT.
If P ′, then VA = 3 + | VTP ′ |

When the potential of the pull-up control signal S _u becomes 5V, the P-type MOS transistor 31 of the pull-up circuit 30 is turned off. In addition, the pull-down control signal S
_{Since the d} (second control signal S ₂ ) is 3V, the N-type MOS transistor 41 of the pull-down circuit 40 has a gate potential of 3V.
It becomes V and turns on. Since the P-type MOS transistor 31 is off, the N-type MOS transistor 41 is on, and the source of the N-type MOS transistor 41 is grounded, the potential of the output pad OUT is “L”.
(0V).

As described above, when the "H" (3V) enable signal is input to the enable terminal EN and the "L" (0V) input signal is input to the input terminal IN, "L" is output from the output pad section OUT. "(0V) is output.
In FIG. 3, a MOS transistor that is turned on when “L” is output from the output pad section OUT is surrounded by a broken line.

At this time, the voltage of 5 V is not applied to the gate oxide film of any of the MOS transistors forming the output circuit, and the gate oxide film is not destroyed or deteriorated.

That is, from the output pad section OUT to "L"
When outputting (0 V), the N-type MOS transistor 24
While the potential of the node B becomes 5 V while the potential of the gate becomes 0 V, due to the existence of the N-type MOS transistor 28 in which the first potential VDD1, that is, 3 V is applied to the gate,
The voltage (VD24) applied to the drain of the N-type MOS transistor 24 does not become 5V, and if the threshold voltage of the N-type MOS transistor considering the substrate bias effect is VTN ', then VD24 = 3-VTN'. Therefore, the gate-drain voltage of the N-type MOS transistor 24 becomes (3-VTN ') V, which is 5
It does not become V and is 3 V or less.

Further, since the potential of the node B becomes 5V and the potential of the node A becomes (3 + │VTP'│) V, the P-type MOS
The voltage between the gate and drain of the transistor 22 (VDG2
2) and the absolute value of the gate-source voltage (VGS21) of the P-type MOS transistor 21 becomes | VDG22 | = | VGS21 | = | (3+ | VTP '|) -5 | = 2- | VTP' | It does not become 5V but is 3V or less.

Further, the gate potential of the P-type MOS transistor 31 becomes 5V, and the potential of the output pad portion OUT becomes 0V.
However, when the first potential VDD1 is applied to the gate P
The presence of the p-type MOS transistor 32
The drain potential VD31 of the transistor 31 becomes VD31 = 3 + | VTP '|, and the absolute value of the gate-drain voltage (VDG31) of the P-type MOS transistor 31 is | VDG31 | = | (3+ | VTP' |) -5 | = 2- | VTP '|, which is not 5V but 3V or less.

Next, the operation for setting the output pad section OUT in the high impedance state will be described. In this case, an "L" (0V) enable signal is input to the enable terminal EN.

Then, the output signal of the NAND gate 11, that is, the first control signal S ₁ becomes "H" (3V), and N
The output signal of the OR gate 12, that is, the second control signal S ₂
Becomes "L" (0V). In this case, the voltage conversion circuit 20
Performs the same operation as when "H" is output from the output pad section OUT, the potential of the node A is (3+ | VTP '
|) And the potential of the node B, that is, the pull-up control signal S
_u becomes 5V. Therefore, P of the pull-up circuit 30
The type MOS transistor 31 is turned off because its gate potential is 5V, while the N type MOS transistor 41 of the pull-down circuit 40 is also turned off because its gate potential is 0V, and the output pad section OUT is in a high impedance state. .

In this state, even if 5V or 0V is externally applied to the output pad section OUT, as in the case of outputting "H" or "L" from the output pad section OUT, which MOS
The voltage of 5 V is not applied to the gate oxide film of the transistor, and the gate oxide film is not destroyed or deteriorated.

As described above, according to the output circuit of the present reference example , a signal having an amplitude of 5V can be output without applying a voltage of 5V to the gate oxide films of all the MOS transistors. Generally speaking, according to the output circuit of the present reference example , even if the power supply voltage of the external LSI is equal to or higher than the gate oxide film breakdown voltage of the MOS transistors forming the output circuit, the gate oxide film of each MOS transistor is not less than the breakdown voltage. It is possible to output a signal having an amplitude of the power supply voltage of the external LSI without applying the voltage.

The output circuit according to the present reference example may have a structure as shown in FIG. 4, the voltage conversion circuit 20 is the voltage conversion circuit 20 in the output circuit shown in FIG.
The N-type MOS transistor 23 is omitted from the configuration, and the output line of the inverter circuit 29 is directly connected to the source of the N-type MOS transistor 27. The output circuit shown in FIG. 4 has the same effect as that of the output circuit shown in FIG. 1, and the number of N-type MOS transistors can be reduced by one.

( Second Reference Example ) FIG. 5 is a circuit diagram showing a configuration of an output circuit according to a second reference example of the present invention. The difference from the output circuit according to the first reference example shown in FIG. 1 is that the P-type MO that constitutes the voltage conversion circuit 20.
The first potential VDD1 is not applied to the gates of the S-transistors 25 and 26 and the P-type MOS transistor 32 forming the pull-up circuit 30, but instead the third potential VDD3 is applied.
The point is that the voltage is applied.

5, the same components as those of the output circuit according to the first reference example shown in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and detailed description thereof will be omitted in this reference example .

The output circuit shown in FIG. 5 is the first reference shown in FIG.
It operates in the same manner as the output circuit according to the example , and the output pad unit OU
The ON / OFF state of each MOS transistor when outputting “H” (5V) or “L” (0V) from T and when setting the output pad section OUT in a high impedance state is similar.

However, the P-type MOS transistors 25 and 2
Since the third potential VDD3 is applied to the gates of 6, 32, the gate potentials of these P-type MOS transistors can be set freely.

Here, the first potential VDD1 is set to 3V,
The second potential VDD2 is set to 5V. When the first potential VDD1 is applied to the gates of the P-type MOS transistors 25, 26, 32 as in the output circuit shown in FIG. 1, the gate-source voltage VGS of the P-type MOS transistors 25, 26, 32 becomes , VGS = VDD1-VDD2 = 3-5 = -2.

The drain current I _dsp at the saturation operation of the P-type MOS transistor is I _dsp = (β _p / 2) × (when the transistor gain coefficient is β _p and the threshold voltage when the substrate bias is 0 V is VTP. VGS-VTP) ² . That is, the drain current of the P-type MOS transistor can be increased as the gate-source voltage VGS is increased within the range permitted by the LSI process.

Assuming that the maximum value of the gate-source voltage allowed in the LSI process is 3.6 V, for example, the output circuit shown in FIG. Gate-source voltage VGS 'of the MOS transistors 25, 26, 32
Becomes VGS '= VIN-VDD2 = 1.4-5 = -3.6, which is the maximum value within the range allowed in the LSI process. The drain current ratio for the output circuit shown in FIG. 1 is {-3.6-(-0.6)} ² /{-2-(-0.6)} ² = if VTP is -0.6V. 9 / 1.96 = 4.59, and the drain current of the P-type MOS transistor is shown in FIG.
It can be 4.59 times that of the output circuit shown in FIG. As the drain current increases, the operation of the output circuit becomes faster.

The third potential VDD3 may be given from the outside of the LSI in which the output circuit is formed, or
A voltage generation circuit that generates the third potential VDD3 may be provided inside the.

As in the modification shown in FIG. 4 in the first reference example , the N-type MOS transistor 23 is deleted from the voltage conversion circuit 20 and the N-type MOS transistor 27 is removed.
The output line of the inverter circuit 29 may be connected to the source of the.

( First Embodiment ) FIG. 6 is a circuit diagram showing a configuration of an output circuit according to a first embodiment of the present invention. The difference from the output circuit according to the second reference example shown in FIG. 5 is that P-type MOS transistors 25 and 26 of the voltage conversion circuit 20 and P-type MO of the pull-up circuit 30.
Third potential VD applied to the gate of the S transistor 32
A configuration in which D3 is set to a predetermined potential VIN or a ground potential by the switch circuit 58 according to the potential difference detection signal OUT1 output from the potential difference detection circuit 50 that detects the potential difference between the first potential VDD1 and the second potential VDD2. That is the point.

6, the same components as those of the output circuit according to the second reference example shown in FIG. 5 are designated by the same reference numerals as those in FIG. 5, and the detailed description thereof will be omitted in the present embodiment.

The output circuit shown in FIG. 6 corresponds to the first reference shown in FIG.
When the output circuit according to the example and the output circuit according to the second reference example shown in FIG. 5 operate in the same manner and output “H” (5V) or “L” (0V) from the output pad section OUT, The same applies to the ON / OFF state of each MOS transistor when the pad portion OUT is set to the high impedance state.

The switch circuit 58 is a potential difference detection circuit 50.
According to the potential difference detection signal OUT1 output from the second
When the potential VDD2 is higher than the first potential VDD1, the predetermined potential VIN is applied to the gates of the P-type MOS transistors 25, 26 and 32 as the third potential VDD3, while the second potential VDD2 is the first potential VDD2. When the potential is VDD1 or less, the gates of the P-type MOS transistors 25, 26, 32 are grounded.

The purpose of having the configuration as shown in FIG. 6 will be described.

Assuming that the first potential VDD1 is 3V, the output circuit according to the present invention can be operated by another L operating with a 5V power supply.
When it is always connected to SI (that is, the second potential VDD2 is always 5 V), there is no particular problem with the configuration shown in FIG. 1 or FIG. 5, but depending on the user (user), the present invention can be applied. It is sometimes possible to use the output circuit by connecting it to another LSI that operates with a 3V power supply. in this case,
That is, when both the first potential VDD1 and the second potential VDD2 are 3V and the output circuit having the configuration shown in FIG. 1 or 5 is used, the drain current flowing through the MOS transistor becomes extremely small, and the operating speed becomes Will decrease.

For example, in the output circuit shown in FIG.
And the third potential VDD3 is 1.4V.
Assuming V, P-type MOS transistors 25, 26, 32
The gate-source voltage VGS of the second potential VDD2
Is 5V, as described in the second reference example , -3.6.
V. However, when the second potential VDD2 is 3V, the gate-source voltage VGS of the P-type MOS transistors 25, 26, 32 is VGS = VDD3-VDD2 = 1.4-3 = -1.6. The ratio of the drain currents of the P-type MOS transistors 25, 26, 32 when the second potential VDD2 is 5 V and 3 V is {-1.6-(-0.6)} ² / {-3. 6 − (− 0.6)} ² = 1/9 = 0.11, and when the second potential VDD2 becomes 3V, the drain current is 0.11 as compared with the case where the second potential VDD2 is 5V.
It will be doubled.

On the other hand, according to the output circuit of this embodiment shown in FIG. 6, the second potential VDD2 changes from the first potential VDD1.
In the following cases, since the gates of the P-type MOS transistors 25, 26, 32 are grounded by the switch circuit 58, for example, the second potential VDD2 is the same as the first potential VDD1.
Even if V, P-type MOS transistors 25, 26, 3
The gate-source voltage VGS of 2 is VGS = VDD3-VDD2 = 0-3 = -3. The ratio of the drain currents of the P-type MOS transistors 25, 26, 32 when the second potential VDD2 is 5V and 3V is {-3.0-(-0.6)} ² / {-3. 6-(-0.6)} ² = 5.76 / 9 = 0.64. In the output circuit shown in FIG. 5, the drain current is 0.1.
Compared with the one-time reduction, the output circuit according to the present embodiment shown in FIG. 6 only reduces the drain current by 0.64 times. Therefore, the decrease in operating speed due to the change in the second potential VDD2 is significantly improved.

FIG. 7 is a circuit diagram showing a detailed structure of the potential difference detection circuit 50.

[0094] In FIG. 7, 51 and 52 are P-type MOS transistor, a seventh P in claim 3, respectively
Type MOS transistor and an eighth P-type MOS transistor. Also, 53, 54, 55, 56 are N-type MOs.
It is S transistor, the seventh in claim 3, respectively
N-type MOS transistor, eighth N-type MOS transistor, ninth N-type MOS transistor, tenth N-type M transistor
It corresponds to an OS transistor. Further, 57 has a high resistance.

In the P-type MOS transistor 51, the first potential VDD1 is applied to the gate, the second potential VDD2 is applied to the source and the substrate, and the drain is the N-type MOS transistor.
It is connected to the drain of the transistor 53. P type M
The gate of the OS transistor 52 is connected to the source of the N-type MOS transistor 56, and the substrate has the second potential VD.
D2 is supplied, the source is supplied with the first potential VDD1, and the drain is connected to the drain of the N-type MOS transistor 56, and the drain is connected to the drain of the N-type MOS transistor 55 and the gate of the N-type MOS transistor 54. The potential difference detection signal OUT1 is output from this connection point.

In the N-type MOS transistor 53, the first potential VDD1 is applied to the gate and the P-type MO transistor is applied to the drain.
It is connected to the drain of the S transistor 51, and the source is N
Connected to the drain of the N-type MOS transistor 54 and the gate of the N-type MOS transistor 55, and the substrate is grounded. The N-type MOS transistor 54 has a P-type M gate
It is connected to the drain of the OS transistor 52 and the drain of the N-type MOS transistor 55, and the drain is an N-type MO transistor.
It is connected to the source of the S transistor 53 and the gate of the N-type MOS transistor 55, and the substrate and the source are grounded. The gate of the N-type MOS transistor 55 is connected to the source of the N-type MOS transistor 53 and the drain of the N-type MOS transistor 54, and the drain thereof is a P-type MO transistor.
It is connected to the drain of the S transistor 52 and the gate of the N-type MOS transistor 54, and the substrate and the source are grounded.

In the N-type MOS transistor 56, the gate is applied with the second potential VDD2, the drain is applied with the first potential VDD1, and the source is connected to the gate of the P-type MOS transistor 52. Is grounded. The high resistance 57 has an N-type MOS transistor 5 at one end.
6 and the gate of the P-type MOS transistor 52, and the other end is grounded.

Regarding the potential difference detection circuit 50 shown in FIG.
The operation will be described with reference to FIGS. 8 and 9.

First, the second potential VDD2 is the first potential V
When the potential is higher than DD1, for example, the second potential VD
The operation when D2 is 5V and the first potential VDD1 is 3V will be described.

At this time, the P-type MOS transistor 51
Turns on because the gate potential is the first potential VDD1 or 3V and the source and substrate potentials are the second potential VDD2 or 5V. On the other hand, since the substrate potential is 0V, the drain potential is the first potential VDD1 or 3V, and the gate potential is the second potential VDD2 or 5V, the N-type MOS transistor 56 is turned on and the source potential is 3V. become. The source potential of the P-type MOS transistor 52 is the first potential VDD1, that is, 3V.
And the substrate potential is the second potential VDD2, that is, 5
Since it is V and the gate potential is the source potential of the N-type MOS transistor 56, that is, 3 V, it is turned off. Further, the N-type MOS transistor 53 is turned on because the gate potential is the first potential VDD1, that is, 3V.

P-type MOS transistor 51 and N-type MO
By turning on the S transistor 53, an N-type MOS
The gate potential of the transistor 55 rises and the N-type MOS transistor 55 turns on. When the N-type MOS transistor 55 is turned on, the gate potential of the N-type MOS transistor 54 becomes the ground potential, and the N-type MOS transistor 54 is turned off.

Therefore, as shown in FIG. 8, when the second potential VDD2 is higher than the first potential VDD1, the P-type MOS transistor 51 and the N-type MOS transistors 53, 55 and 56 are turned on. Naruto and P-type MO
The S transistor 52 and the N-type MOS transistor 54 are turned off, and the potential difference detection signal OUT1 becomes the ground potential, that is, 0V. In FIG. 8, a MOS that is turned on when the second potential VDD2 is higher than the first potential VDD1.
The transistor is surrounded by a broken line.

Next, the second potential VDD2 is changed to the first potential V
The operation when DD1 or less, for example, when the second potential VDD2 and the first potential VDD1 are both 3V will be described.

At this time, the P-type MOS transistor 51 is turned off because the potentials of the gate, the source and the substrate are all 3V. On the other hand, since the N-type MOS transistor 56 has a substrate of 0V and a gate and a drain of 3V, the N-type MOS transistor 56 operates as a source follower, and the source potential VS has a threshold voltage VTN ′ considering the substrate bias effect of 0.9V, for example. , VS = VDD2-VTN ′ = 3-0.9 = 2.1.

As a result, the P-type MOS transistor 52
Turns on because the gate potential is 2.1V and the source and substrate potentials are 3V. When the P-type MOS transistor 52 is turned on, the N-type MOS transistor 5
The gate potential of 4 rises, and the N-type MOS transistor 54
Turns on. When the N-type MOS transistor 54 is turned on, the gate potential of the N-type MOS transistor 55 becomes the ground potential, and the N-type MOS transistor 55 is turned off.

Therefore, as shown in FIG. 9, when the second potential VDD2 is the same potential as the first potential VDD1, the P-type MOS transistor 52 and the N-type MOS transistors 53 and 54 are turned on and P The type MOS transistor 51 and the N type MOS transistor 55 are turned off, and the potential difference detection signal OUT1 becomes 3V. In Figure 9,
A dashed line surrounds the MOS transistor that is turned on when the second potential VDD2 is the same as the first potential VDD1. The N-type MOS transistor 56 is in a weak ON state.

Further, the potential difference detecting circuit 50 shown in FIG.
Is configured such that even if the second potential VDD2 is higher than the first potential VDD1, the gate oxide film of each MOS transistor does not receive a voltage equal to or more than the potential difference between the first potential VDD1 and the ground potential. ing.

For example, when the first potential VDD1 is 3V and the second potential VDD2 is 5V, the N-type MOS transistor 56 has a substrate potential of 0V, a source and drain potential of 3V, and a gate potential of 5V. However, the voltage applied to the gate oxide film is 2V because it is in the ON state and the inversion layer (3V in this example) is generated on the substrate. Also, P
The potential of the substrate, the source and the drain of the type MOS transistor 51 is 5V, but the gate potential is 3V, so the voltage applied to the gate oxide film is 2V. The N-type MOS transistor 53 has a drain potential of 5V and a substrate potential of 0.
However, the voltage applied to the gate oxide film is 2 V or less because the gate potential is 3 V, the gate potential is on, and the substrate has an inversion layer.

As described above, the potential difference detection circuit 50 has the second
When the second potential VDD2 is higher than the first potential VDD1, “L” is output as the potential difference detection signal OUT1, while when the second potential VDD2 is the same potential as the first potential VDD1, the potential difference detection is performed. "H" as signal OUT1
Is output. Moreover, no voltage higher than the potential difference between the first potential VDD1 and the ground potential is applied to the gate oxide film of each transistor.

According to the potential difference detection signal OUT1 of the potential difference detection circuit 50, the switch circuit 58, when the second potential VDD2 is higher than the first potential VDD1, outputs the P-type MOS transistors 25, 26 ,. A predetermined potential VIN is applied as the third potential VDD3 to the gate of 32, while the second potential VDD2 is changed to the first potential VDD1.
When it is below, P-type MOS transistors 25, 2
Ground the gates of 6, 32. With such a configuration, the output circuit can operate at high speed even when the second potential VDD2 drops. Therefore, regardless of whether the connected external LSI is a 3V operating circuit or a 5V operating circuit, high-speed operation can be always maintained, and an output circuit having a wide operable voltage range can be provided.

( Second Embodiment ) FIG. 10 is a circuit diagram showing a configuration of an output circuit according to a second embodiment of the present invention. In the output circuit shown in FIG.
Node C and node A, which are connection points between the drain of the N-type MOS transistor 23 and the source of the N-type MOS transistor 27.
And N-type MOS transistors 61 and 62 are connected in series between them, and between a node D and a node B which is a connection point between the drain of the N-type MOS transistor 24 and the source of the N-type MOS transistor 28. N-type MOS transistors 63 and 64 are connected in series. A first potential VDD1 is applied to the gates of the N-type MOS transistors 61 and 63, and a potential difference detection that detects a potential difference between the first potential VDD1 and the second potential VDD2 is applied to the gates of the N-type MOS transistors 62 and 64. Potential difference detection signal OUT of circuit 50
1 is input.

Except for these points, the configuration is the same as that of the output circuit according to the second reference example shown in FIG. 5, and the same components as those in FIG. In the form, detailed description thereof will be omitted. N-type MOS transistors 61, 62,
A voltage conversion promoting circuit is configured by 63 and 64, and N-type MOS transistors 61, 62, 63 and 64 are provided.
Respectively correspond to the 11 N-type MOS transistor, the first 12 N-type MOS transistor, N-type MOS transistor 13, and the 14 N-type MOS transistor according to claim 6.

The output circuit according to the present embodiment aims to improve the characteristics when the second potential VDD2 is equal to or lower than the first potential VDD1. Specifically, the delay time when "H" is output from the output pad section OUT is shortened.

The potential difference detection circuit 50 has the second potential VDD.
When 2 is higher than the first potential VDD1, “L” (0V) is output as the potential difference detection signal OUT1, while when the second potential VDD2 is equal to or lower than the first potential VDD1, the potential difference detection signal is output. “H” (VDD
1) is output.

Therefore, when the second potential VDD2 is higher than the first potential VDD1, the N-type MOS transistors 62 and 64 are turned off, so that the nodes A and C and the nodes B and D are bypassed. Not done. On the other hand, when the second potential VDD2 is less than or equal to the first potential VDD1, the N-type M
Since the OS transistors 62 and 64 are turned on, the node A
A bypass consisting of N-type MOS transistors 61 and 62 is formed between −C and N-type MO between nodes BD.
A bypass composed of S transistors 63 and 64 is formed.

When "H" is output from the output pad section OUT, the potential of the node B (pull-up control signal Su) falls, but at this time, the N-type MOS transistors 63, 64.
Since the potential of the node B is lowered by the bypass consisting of, there is no bypass like the output circuit shown in FIG.
It falls faster than when it is pulled down only by the OS transistor 26. Moreover, the potential of the node B at "L" changes from (VDD3 + | VTP '|) V to 0V.
The P-type MOS transistor 31 of the pull-up circuit 30 is
Since the gate potential becomes 0 V, the voltage between the gate and the source becomes large, so that the drain current becomes large. Therefore, the fall of the potential of the node B becomes faster and the drain current of the P-type MOS transistor 31 becomes larger, so that the delay time when "H" is output from the output pad section OUT becomes shorter.

FIG. 11 is a circuit diagram showing a configuration of a modified example of the output circuit according to this embodiment. Compared to FIG. 10, N
Type MOS transistors 61 and 62 are connected in series between the node A and the output line of the inverter circuit 29, and N type MOS transistors 63 and 64 are connected in series between the node B and the input line of the inverter circuit 29. The difference is that they are connected.

The second potential VDD2 is the first potential VDD1.
In the following cases, the N-type MOS transistors 62 and 64 are turned on, so that a bypass consisting of the N-type MOS transistors 61 and 62 is formed between the node A and the output line of the inverter circuit 29, and the node B and the inverter are formed. Circuit 29
A bypass including N-type MOS transistors 63 and 64 is formed between the input line and the input line.

When "H" is output from the output pad section OUT, the potential of the node A becomes "H" and the potential of the node B (pull-up control signal ^Su ) becomes "L", but the signal generation circuit 10 Since the first control signal S ¹ output from is "L", the output signal of the inverter circuit 29 becomes "H", and the potential of the node A is pushed up through the bypass. Therefore, the delay time until the potential of the node A becomes "H" is shortened, and the circuit operates faster than the output circuit shown in FIG.

FIG. 12 is a circuit diagram showing the configuration of a modification of the output circuit according to this embodiment, which is an eclectic combination of FIG. 10 and FIG. 12, N-type MOS transistors 61 and 62 are connected in series between the node A and the output line of the inverter circuit 29 as in FIG.
The MOS transistors 63 and 64 are connected in series between the node B and the node D as in FIG.

[0121]

As described above, according to the output circuit of the present invention, even if the power supply voltage of the external LSI is equal to or higher than the gate oxide film breakdown voltage of the MOS transistor forming the output circuit, the gate oxide film of each MOS transistor is formed. Since a signal having the amplitude of the power supply voltage of the external LSI can be output without applying a voltage higher than the withstand voltage to the gate, the gate oxide film is not destroyed or deteriorated.

In addition, the second P that constitutes the pull-up circuit
Gates of the fifth and sixth P-type MOS transistors forming the voltage conversion circuit
By setting the drain current of the transistor to a larger value, the output circuit according to the present invention can operate at higher speed.

Further, by providing the potential difference detection circuit and the switch circuit, the gate potentials of the second, fifth and sixth P-type MOS transistors are set to the ground potential when the second potential is equal to or lower than the first potential. can do. Therefore, the output circuit according to the present invention can operate at high speed by increasing the drain current of the MOS transistor even when the second potential decreases, and an output circuit having a wide potential range capable of high-speed operation is provided. You can

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of an output circuit according to a first reference example of the present invention.

FIG. 2 is a circuit diagram showing a configuration of an output circuit according to a first reference example of the present invention, showing an operation when an output potential of an output pad section is a high potential.

FIG. 3 is a circuit diagram showing a configuration of an output circuit according to a first reference example of the present invention, and is a diagram showing an operation when an output potential of an output pad section is a low potential.

FIG. 4 is a circuit diagram showing a configuration of a modified example of the output circuit according to the first reference example of the present invention.

FIG. 5 is a circuit diagram showing a configuration of an output circuit according to a second reference example of the present invention.

FIG. 6 is a circuit diagram showing a configuration of an output circuit according to the first embodiment of the present invention.

FIG. 7 is a circuit diagram showing a detailed configuration of a potential difference detection circuit in the output circuit according to the first embodiment of the present invention.

FIG. 8 is a circuit diagram showing a detailed configuration of a potential difference detection circuit in the output circuit according to the first embodiment of the present invention, showing an operation when the second potential is higher than the first potential. is there.

FIG. 9 is a circuit diagram showing a detailed configuration of a potential difference detection circuit in the output circuit according to the first embodiment of the present invention, showing an operation when the second potential is equal to or lower than the first potential. is there.

FIG. 10 is a circuit diagram showing a configuration of an output circuit according to a second embodiment of the present invention.

FIG. 11 is a circuit diagram showing a configuration of a modified example of the output circuit according to the second embodiment of the present invention.

FIG. 12 is a circuit diagram showing a configuration of a modified example of the output circuit according to the second embodiment of the present invention.

FIG. 13 is a circuit diagram showing a configuration of a conventional output circuit.

FIG. 14 is a circuit diagram showing a configuration of a conventional output circuit,
It is a figure which shows operation | movement when the output electric potential of an output pad part is a high electric potential.

FIG. 15 is a circuit diagram showing a configuration of a conventional output circuit,
It is a figure which shows operation | movement when the output electric potential of an output pad part is a low electric potential.

[Description of Reference Signs] IN input terminal EN enable terminal OUT output pad section (output section) VDD1 first potential VDD2 second potential VDD3 third potential VIN predetermined potential OUT1 potential difference detection signal A node B node 10 signal generation circuit S ₁ First control signal S ₂ Second control signal _Su Pull-up control signal S _d Pull-down control signal 20 Voltage conversion circuit 21 P-type MOS transistor (third P-type MOS transistor) 22 P-type MOS transistor (third 4 P-type MOS transistor) 23 N-type MOS transistor (sixth N-type MOS transistor) 24 N-type MOS transistor (fourth N-type MOS transistor) 25 P-type MOS transistor (fifth P-type MOS transistor) 26 P-type MOS transistor (sixth P-type MOS transistor) 27 N-type MOS Transistor (fifth N-type MOS transistor) 28 N-type MOS transistor (third N-type MOS transistor) 30 Pull-up circuit 31 P-type MOS transistor (first P-type MOS transistor) 32 P-type MOS transistor (second) P-type MOS transistor) 40 Pull-down circuit 41 N-type MOS transistor (first N-type MOS transistor) 42 N-type MOS transistor (second N-type MOS transistor) 50 Potential difference detection circuit 51 P-type MOS transistor (seventh P-type MOS transistor) 52 P-type MOS transistor (eighth P-type MOS transistor) 53 N-type MOS transistor (seventh N-type MOS transistor) 54 N-type MOS transistor (eighth N-type MOS transistor) 55 N-type MOS transistor (9th N-type MOS transistor) 56 N-type MOS transistor (tenth N-type MOS transistor) 58 Switch circuit 61 N-type MOS transistor (11th N-type MOS transistor) 62 N-type MOS transistor (12th N-type MOS transistor) 63 N-type MOS transistor (13th N-type MOS transistor) 64 N-type MOS transistor (14th N-type MOS transistor)

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-7-74616 (JP, A) JP-A-6-37624 (JP, A) JP-A-7-111450 (JP, A) International Publication 95/019660 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) H03K 19/00 H03K 17/00

Claims (8)

(57) [Claims] 1. A circuit for using a first potential as a power supply potential
Use the output signal as input and follow the output signal of this one circuit.
From the output to another circuit that uses the second potential as the power supply potential.
An output circuit for outputting a signal, the first circuit based on the input output signal of the one circuit,
1st and 1st whose amplitude is the potential difference between the first potential and the ground potential
A signal generation circuit for generating a second control signal, the first control signal generated by the signal generating circuit
As an input, to convert the amplitude of this first control signal
Voltage conversion circuit that generates and outputs a more pull-up control signal
And a pull-up control signal output from the voltage conversion circuit.
As an input, follow the instructions of this pull-up control signal
It controls whether or not the potential of the output section is raised to the second potential.
And a pull-up circuit for controlling the second control signal generated by the signal generation circuit.
Input as a pull-down control signal to control this pull-down
Pull the potential of the output section to the ground potential according to the signal instructions.
A pull-down circuit for controlling whether or not to lower the voltage, the pull-up circuit being provided with the second potential at a source and the pull-up circuit at a gate.
First P-type MOS transistor to which a pull-up control signal is input
A transistor and a drain of the first P-type MOS transistor.
Source to the output and the drain to the output
A third gate connected to the gate and different from the first potential
A second P-type MOS transistor to which a potential is applied
In the pull-down circuit, the source is grounded and the gate is the pull-down control signal.
A first N-type MOS transistor to which
Source is connected to the drain of N-type MOS transistor 1
And the drain is connected to the output and
Second N-type MOS transistor to which the first potential is applied
And a voltage converter for increasing the potential of the output unit to the second potential.
When instructing the pull-up circuit,
The potential of the control signal from the second potential to the first P-type M
Below the threshold voltage of the OS transistor and before
From the second potential of the first P-type MOS transistor
Set the potential higher than the gate oxide film withstand voltage equivalent voltage.
Meanwhile, the potential of the output section is raised to the second potential.
If you do not instruct the pull-up circuit to
To set the potential of the loop-up control signal to the second potential
And the output circuit detects a potential difference between the first potential and the second potential,
A potential difference detection circuit that outputs a potential difference detection signal indicating whether or not the second potential is higher than the first potential, and a potential difference detection circuit that is supplied with a predetermined potential and a ground potential and that is output from the potential difference detection circuit. When the signal is an input and the potential difference detection signal indicates that the second potential is larger than the first potential, the predetermined potential is selected and output, while the potential difference detection signal indicates that the second potential is A switch circuit which selectively outputs a ground potential when the output potential is equal to or lower than the first potential, and the output potential of the switch circuit is the third potential. 2. The output circuit according to claim 1 , wherein the predetermined potential is less than or equal to the first potential and the second potential is less than or equal to the first potential.
The output circuit has a potential equal to or higher than a potential obtained by subtracting a voltage equivalent to the gate oxide film withstand voltage of the first P-type MOS transistor from the potential. 3. The output circuit according to claim 1 , wherein the potential difference detection circuit is a seventh P-type MOS transistor in which the source is applied with the second potential and the gate is applied with the first potential. And an eighth P-type MOS having the source supplied with the first potential
A transistor, a seventh N-type MOS transistor in which the drains of the seventh P-type MOS transistor are connected to each other, and a drain of which is connected to the source of the seventh N-type MOS transistor and the source of which is grounded An N-type MOS transistor, a ninth N-type MOS transistor whose drain is connected to the eighth P-type MOS transistor and whose source is grounded, and said first potential is applied to the drain and said gate is applied to the gate. A tenth N-type MOS transistor to which a second potential is applied and whose source is connected to the gate of the eighth P-type MOS transistor, wherein the gate of the eighth N-type MOS transistor and the ninth
Is connected to the drain of the N-type MOS transistor, the gate of the ninth N-type MOS transistor is connected to the drain of the eighth N-type MOS transistor, and the eighth P-type MOS transistor and the eighth N-type MOS transistor are connected to each other. N type M of 9
An output circuit, which outputs the potential difference detection signal from a node in which drains of an OS transistor and drains are connected to each other. 4. The output circuit according to claim 3 , wherein the substrate potentials of the seventh and eighth P-type MOS transistors are the second potential, and the seventh, eighth, ninth and ninth 10. The output circuit, wherein the substrate potential of the N-type MOS transistor 10 is ground potential. 5. A circuit for using the first potential as a power supply potential
Use the output signal as input and follow the output signal of this one circuit.
From the output to another circuit that uses the second potential as the power supply potential.
An output circuit for outputting a signal, the first circuit based on the input output signal of the one circuit,
1st and 1st whose amplitude is the potential difference between the first potential and the ground potential
A signal generation circuit for generating a second control signal, the first control signal generated by the signal generating circuit
As an input, to convert the amplitude of this first control signal
Voltage conversion circuit that generates and outputs a more pull-up control signal
And a pull-up control signal output from the voltage conversion circuit.
As an input, follow the instructions of this pull-up control signal
It controls whether or not the potential of the output section is raised to the second potential.
And a pull-up circuit for controlling the second control signal generated by the signal generation circuit.
Input as a pull-down control signal to control this pull-down
Pull the potential of the output section to the ground potential according to the signal instructions.
A pull-down circuit for controlling whether or not to lower the voltage, the pull-up circuit being provided with the second potential at a source and the pull-up circuit at a gate.
First P-type MOS transistor to which a pull-up control signal is input
A transistor and a drain of the first P-type MOS transistor.
Source to the output and the drain to the output
A third gate connected to the gate and different from the first potential
A second P-type MOS transistor to which a potential is applied
In the pull-down circuit, the source is grounded and the gate is the pull-down control signal.
A first N-type MOS transistor to which
Source is connected to the drain of N-type MOS transistor 1
And the drain is connected to the output and
Second N-type MOS transistor to which the first potential is applied
And a voltage converter for increasing the potential of the output unit to the second potential.
When instructing the pull-up circuit,
The potential of the control signal from the second potential to the first P-type M
Below the threshold voltage of the OS transistor and before
From the second potential of the first P-type MOS transistor
Set the potential higher than the gate oxide film withstand voltage equivalent voltage.
Meanwhile, the potential of the output section is raised to the second potential.
If you do not instruct the pull-up circuit to
To set the potential of the loop-up control signal to the second potential
And the output circuit detects a potential difference between the first potential and the second potential,
A potential difference detection circuit that outputs a potential difference detection signal indicating whether or not the second potential is higher than the first potential, and a potential difference detection signal output from the potential difference detection circuit as an input, and the potential difference detection signal is When indicating that the second potential is higher than the first potential, the operation speed of the voltage conversion circuit is accelerated, while the potential difference detection signal indicates that the second potential is equal to or lower than the first potential. And an output circuit that does not accelerate the operating speed of the voltage conversion circuit. 6. The output circuit according to claim 5 , wherein the voltage conversion circuit includes third and fourth P-type transistors having a source to which the second potential is applied.
Type MOS transistor, a fifth P-type MOS transistor whose source is connected to the drain of the third P-type MOS transistor, and a sixth P-type transistor whose source is connected to the drain of the fourth P-type MOS transistor. -Type MOS transistor, a third N-type MOS transistor having the sixth P-type MOS transistor and drains connected to each other, a drain connected to the source of the third N-type MOS transistor, and a source grounded A fourth N-type MOS transistor, a fifth N-type MOS transistor in which the fifth P-type MOS transistor and the drains thereof are connected to each other, and a drain and a source of the fifth N-type MOS transistor And a sixth N-type MOS transistor whose ground is connected to the ground. And the fourth
Is connected to the drain of the P-type MOS transistor, and the gate of the fourth P-type MOS transistor is connected to the drain of the third P-type MOS transistor, and the fifth and sixth P-type MOS transistors are connected. The third potential is applied to the gate of the second N-type MOS transistor, the first potential is applied to the gates of the third and fifth N-type MOS transistors, and the signal generation is applied to the gate of the sixth N-type MOS transistor. A first control signal generated by a circuit is input, an inverted signal of the first control signal is input to the gate of the fourth N-type MOS transistor, and a drain of the fourth P-type MOS transistor is input. The pull-up control signal is output from a node connected to the source of the sixth P-type MOS transistor. The circuit includes an eleventh N-type MOS transistor whose drain is connected to the third P-type MOS transistor, and a sixth N-type MOS transistor whose drain is connected to the source of the eleventh N-type MOS transistor. A twelfth N-type MOS transistor whose source is connected to the drain of the transistor, a thirteenth N-type MOS transistor whose drain is connected to the fourth P-type MOS transistor, and the thirteenth N-type MOS transistor A fourteenth N-type MOS transistor having a drain connected to the source and a source connected to the drain of the fourth N-type MOS transistor, wherein the gates of the eleventh and thirteenth N-type MOS transistors are A twelfth and fourteenth potential is applied to the first potential.
The potential difference detection signal is input to the gate of the N-type MOS transistor, and the potential difference detection circuit detects the first potential difference when the second potential is higher than the first potential. An output circuit, which outputs the signal as a signal, and outputs the ground potential as the potential difference detection signal when the second potential is equal to or lower than the first potential. 7. The output circuit according to claim 6 , wherein the source of the twelfth N-type MOS transistor is connected to the drain of the sixth N-type MOS transistor instead of the first control signal. An output circuit characterized by receiving an inverted signal. 8. The output circuit according to claim 7 , wherein the source of the fourteenth N-type MOS transistor is connected to the drain of the fourth N-type MOS transistor, and the first control signal is supplied. An output circuit characterized by being input.