JPH05152859A - Semiconductor device - Google Patents

Abstract

PURPOSE:To provide the semiconductor device whose internal circuit is not malfunctioned even when a high frequency signal is inputted to an external connection pad. CONSTITUTION:An output of an operational amplifier 200 is connected to an opposite phase input terminal and an analog circuit 104, and a voltage division voltage of a power supply potential Vdd is given to a same phase input terminal. An output of an operational amplifier 210 is connected to a wiring pad 105 and an opposite phase input terminal of itself and a voltage division voltage of the power supply potential Vdd is given to the same phase input terminal. A high frequency signal inputted to the wiring pad 105 externally is cut off by the operational amplifiers 200, 210 and not delivered to an analog circuit 104 being the internal circuit. Thus, malfunction of the semiconductor device is avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device which is less likely to malfunction due to external noise.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram showing a conventional semiconductor device. In the figure, 101 and 102 are resistors, Vdd is a power supply potential, and Vss is a ground potential. Resistors 101 and 102
Are connected in series between the power supply potential Vdd and the ground potential Vss.

The operational amplifier 103 constitutes a voltage follower. The operational amplifier 103 has an in-phase input end connected to a common connection point of the resistors 101 and 102, and an output end connected to the wiring pad 105, a negative-phase input end of itself, and the analog circuit 104.

Next, the operation will be described. The resistance values of the resistors 101 and 102 are set so that the potential at the common connection point of the resistors 101 and 102 becomes half (1/2) Vdd of the power supply potential Vdd. This potential (1/2) Vdd is given to the in-phase input terminal of the operational amplifier 103, and the output terminal of the operational amplifier 103 is connected to the negative-phase input terminal. M (1/2) Vdd
(Hereinafter, this potential is referred to as Vref). Operational amplifier 1
The analog circuit 104 inside the IC operates with the potential Vref at the output end of 03 as the reference potential, and the analog circuit outside the IC operates through the wiring pad 105.

[0005]

As described above, the conventional semiconductor device has the wiring pad 105 connected to the analog circuit 104 inside the IC and the analog circuit outside the IC.
Since and are commonly connected at the output end of the operational amplifier 103, there is a problem that the analog circuit 104 inside the IC malfunctions when a high frequency is input to the wiring pad 105 from outside the IC.

The present invention has been made to solve the above problems, and an object thereof is to obtain a semiconductor device in which an internal circuit does not malfunction even when a high frequency is input to an external connection pad.

[0007]

A semiconductor device according to the present invention is a semiconductor device which supplies a reference voltage to an external connection pad and an internal circuit via a buffer, wherein a reference voltage is supplied to the external connection pad. 1 buffer,
A second buffer for supplying a reference voltage to the internal circuit.

[0008]

According to the present invention, the first buffer for supplying the reference voltage to the external connection pad and the second buffer for supplying the reference voltage to the internal circuit are provided.
The buffer prevents the high frequency input to the external connection pad from the outside from being transmitted to the internal circuit.

[0009]

1 is a circuit diagram showing a first embodiment of a semiconductor device according to the present invention. In the figure, the difference from the conventional circuit shown in FIG. 4 is that the operational amplifier 103 is eliminated, and operational amplifiers 200 and 210 having a voltage follower configuration are newly provided as buffers. The operational amplifier 200 is
The in-phase input end is connected to the common connection point of the resistors 101 and 102, and the output end is connected to the analog circuit 104 inside the IC and the reverse-phase input end of itself. Operational amplifier 210
Has an in-phase input end connected to a common connection point of the resistors 101 and 102, and an output end connected to the wiring pad 105 and its own negative-phase input end. Other configurations are the same as those of the conventional circuit.

Next, the operation will be described. First, the potential at the common connection point of the resistors 101 and 102 is (1
/ 2) Set to Vdd. Then, the potential of the output terminal of the operational amplifier 200 becomes (1/2) Vdd, and this potential is supplied to the analog circuit 104. The analog circuit 104 operates using this potential as a reference potential. The potential of the output terminal of the operational amplifier 210 also becomes (1/2) Vdd, and this potential is supplied to the external analog circuit via the wiring pad 105, and the analog circuit operates with the potential as a reference voltage.

Since the operational amplifier 200 for supplying the reference voltage to the analog circuit 104 and the operational amplifier 210 for supplying the reference voltage to the wiring pad 105 are separately provided so that the analog circuit 104 and the wiring pad 105 are not directly connected, Even if a high frequency is input to the wiring pad 105, it is not input to the analog circuit 104, and the analog circuit 104 does not malfunction.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention. The difference between the second embodiment and the first embodiment shown in FIG. 1 is that the common-mode input terminal of the operational amplifier 210 is connected to the resistor 101.
And the resistor 102, not the common connection point, but the operational amplifier 20
0 is connected to the output end. Other configurations are shown in FIG.
It is similar to the embodiment shown in FIG.

Also in this embodiment, the analog circuit 104 is used.
Operational amplifier 200 for supplying a reference voltage to the wiring pad 105 and an operational amplifier 210 for supplying a reference voltage to the wiring pad 105.
Are provided separately so that the analog circuit 104 and the wiring pad 105 are not directly connected, and therefore, the same effect as that of the first embodiment is obtained.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention. In the figure, the difference from the first embodiment is that the resistance 1
01 and 102 are eliminated and resistors 101a and 101 are newly added.
b, 102a and 102b are provided. Resistance 10
1a and 102a and resistors 101b and 102b are connected in series between the power supply potential Vdd and the ground potential Vss. The common connection point of the resistors 101a and 102a is connected to the common-mode input terminal of the operational amplifier 210, the resistors 101b,
The common connection point with 102b is connected to the in-phase input terminal of the operational amplifier 200. Other configurations are similar to those of the first embodiment.

Also in this embodiment, the analog circuit 104 is used.
Operational amplifier 200 for supplying the reference voltage to the wiring pad 105 and operational amplifier 210 for supplying the reference voltage to the wiring pad 105
Are provided separately so that the analog circuit 104 and the wiring pad 105 are not directly connected, and therefore, the same effect as that of the first embodiment is obtained.

In the first, second and third embodiments, the operational amplifiers 200 and 210 having the voltage borrower structure are shown as buffers, but the same effect as the above embodiment can be obtained by using the buffers having other structures. Is obtained.

[0017]

As described above, according to the present invention, the first buffer for supplying the reference voltage to the external connection pad and the second buffer for supplying the reference voltage to the internal circuit are provided. The first and second buffers prevent the high-frequency input to the external connection pad from the outside to the internal circuit. As a result, the internal circuit does not malfunction.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing a second embodiment of the semiconductor device according to the present invention.

FIG. 3 is a circuit diagram showing a third embodiment of the semiconductor device according to the present invention.

FIG. 4 is a circuit diagram showing a conventional semiconductor device.

[Explanation of symbols]

 104 analog circuit 105 wiring pad 200, 210 operational amplifier

Claims (1)

[Claims] 1. A semiconductor device which supplies a reference voltage to an external connection pad and an internal circuit via a buffer, and a first buffer which supplies a reference voltage to the external connection pad, and a reference voltage to the internal circuit. And a second buffer for supplying the semiconductor device.