JPH0254546A - Semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To enable measurement of a threshold voltage Vr from an IC terminal by providing a connection switching means of an output terminal which outputs an output of an output buffer connected with a P-channel and N-channel MOS transistor in series to the outside of an IC. CONSTITUTION:A terminal 1 is connected to GND, and a gate of an N-channel transistor 12 attains Low level and an output of the N-channel transistor 12 is in the high impedance state. A variable power source 17 is operated and an electric potential is provided to a gate of a P-channel transistor 11 by providing an electric potential to a terminal 2. In this state, Vr value of the P-channel transistor 11 is measured by measuring a value of an ammeter 16.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a semiconductor integrated circuit (hereinafter referred to as an IC).
The present invention relates to an IC having an output buffer capable of measuring a threshold voltage (hereinafter referred to as V↑).

[Conventional technology]

Conventional ICs have an empty area on the IC chip, and in this area, a single transistor (
The VT value was measured by creating a check transistor (hereinafter referred to as a check transistor) and directly connecting a dedicated measuring device to the check transistor.

[Problem to be solved by the invention]

The conventional IC described above requires a dedicated measuring device to measure the VT value, and the measuring device must be connected directly to the IC chip. It has the disadvantage that it cannot be connected and the VT value cannot be measured.

[Means to solve the problem]

The semiconductor integrated circuit of the present invention includes an output buffer formed by connecting a P-channel MOS transistor and an N-channel MOS transistor in series, and an output buffer that connects the output of the output buffer to an IC.
It includes an output terminal for outputting to the outside, a separate terminal other than the output terminal and the power supply terminal, and means for switching whether to connect an internal signal line of the semiconductor integrated circuit to the gate of the output buffer or to connect the separate terminal. Consists of.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention.

The switching circuit a is a signal that is at a LOW level during normal operation of the IC, and is at a HIGH level when the V side is in regular operation.

During normal operation of the IC, the switching signal a is at a low level, so that transfer gates 4 to 7 are in an ON state, and transfer gates 9 and 10 are in an OFF state. Input signals from terminals 1 and 2 are transmitted inside the IC through transfer gates 4 and 5, and output signals from inside the IC are output through transfer gates 4 and 5 to terminal 1.2. Output buffer transistor 11
12 is isolated from terminal 1.2 by transfer gates 9, 10, and the output of the internal circuit of the IC is transmitted through transfer gate 6.7 to the gate of output buffer transistor 11.12. The above state allows the IC to operate normally.

Since the switching signal a is at a high level when measuring V, the transfer gates 4 to 7 are in the OFF state, and the transfer gates 9 and 10 are in the ON state. The gates of the P-channel transistor 11 and the N-channel transistor 12 constituting the terminals 1 and 2 and the output buffer 13 are insulated from the inside of the IC by transfer gates 4 to 7. The gate of P-channel transistor 11 is connected to terminal 2 by transfer gate 10, and the gate of N-channel transistor 12 is connected to terminal 1 by transfer gate 9. Both transistors can be operated directly by applying a potential to terminals 1 and 2. It becomes possible to do so.

FIG. 2 is a measurement circuit diagram when measuring the VT value of the P-channel transistor 1 in the above state.

Since terminal 1 is connected to GND (ground terminal and low level), the gate of N-channel transistor 12 becomes low level, and N-channel transistor 12
The output becomes a high impedance state. Variable power supply 17
By operating the terminal 2 and applying a potential to the terminal 2, a potential is applied to the gate of the P-channel transistor 11.

In the above state, the VT value of the P-channel transistor 11 is measured by measuring the value of the ammeter 16.

Note that 15 is a fixed power supply that is supplied to the entire semiconductor integrated circuit 14. FIG. 3 is a measurement circuit diagram when measuring the vT value of the N-channel transistor 12.

The method for measuring the VT value of the N-channel transistor 12 is the same as the method for measuring the Vt value of the P-channel transistor 11 described above. However, terminal 2 is connected to VDD, and the output of variable power supply 17 is connected to terminal 1.

〔Effect of the invention〕

As explained above, the present invention makes it possible to measure the VT value from the terminals of the IC, so there is no need for a dedicated measuring device. This has the effect of making it possible to measure the VT value using a socket. Furthermore, since the VT value can be measured using the terminals of the IC, there is an effect that the VT can be measured even in an IC in which an IC chip is encapsulated.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a VT value measurement circuit diagram of a P-channel transistor, and FIG. 3 is a VT value measurement circuit diagram of an N-channel transistor. 1.2.3...IC terminal, 4, 5.6, 7, 9゜1
0...Transfer gate, 8...Inverter,
11...P channel transistor, 12...N channel transistor, 13...output buffer, 14...
- Semiconductor integrated circuit, 15... Fixed power supply, 16... Ammeter, 17... Variable power supply.

Claims (1)

[Claims] an output buffer formed by connecting a P-channel MOS transistor and an N-channel MOS transistor in series; an output terminal for outputting the output of the output buffer to the outside of the IC;
A semiconductor integrated circuit comprising: switching means for connecting an internal signal line of the semiconductor integrated circuit to another terminal other than the output terminal and the power supply terminal and the gate of the output buffer, or connecting the other terminal to the gate of the output buffer.