JPH04103143A - Semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To make it possible to prevent the generation of the erroneous operation of a semiconductor integrated circuit due to a noise or the like by a method wherein the circuit is provided with a decoder, which outputs a signal for controlling a totem pole output buffer and three-state output buffers. CONSTITUTION:Output buffers 2 to 4 receive output control signal and the outputs of the buffers 2 to 4 is each a three-state output buffer which is connected by means of a wired OR connection and are connected to the output part of a buffer 1. In the case where output signals OUT 1 to 3 of a decoder 5 are at an 'L' level, the outputs of the buffers 2 to 4 are brought into the state of a high impedance. In the case where the signals OUT 1 to 3 are at an 'H' level, the outputs of the buffers 2 to 4 are each turned into a signal of a polarity identical with that of the output control signal. An output signal A has driving capacities of IOL=nX1/4X4=nmA and IOH=mX1/4X4=mmA. Accordingly, it is possible to control the driving capacities of the output buffers by the output of the decoder 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor integrated circuit, and particularly to a semiconductor integrated circuit having a multi-bin output buffer.

[Conventional technology]

Conventionally, this type of semiconductor integrated circuit has a circuit configuration that can only be used with a fixed drive current in terms of the drive capability of the output buffer.

[Problem to be solved by the invention]

The above-mentioned conventional semiconductor integrated circuit has the drawback that when testing a custom LSI using an LSI tester, a test pattern in which multiple output bins change simultaneously may cause malfunctions due to noise, etc., and a good product may become defective. be.

[Means to solve the problem]

The semiconductor integrated circuit of the present invention includes a totem pole output buffer that supplies an output current, a 3-state output buffer,
and a decoder that outputs a signal for controlling the 3-state output buffer.

〔Example〕

The invention will now be described with reference to compartments.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In FIG. 1, 1 is I. L=nX-mA,
This is an output buffer that has a driving capability of I as = m X - m A and uses human power as an output control signal. Reference numerals 2 to 4 designate three-state output buffers which receive an output control signal and whose outputs are connected in a wired-or-off manner, and are connected to the output section of the buffer 1. There is also the effect that IOL=nX.

ing. 5 is Enable for output buffers 2 to 4
This is a decoder for outputting signals.

When the output signals 0LJTI-3 of the decoder 5 are "L", the outputs of the output buffers 2-4 are in a high impedance state. In addition, in the case of "H", the outputs of output buffers 2 to 4 become signals with the same polarity as the output control signal, and output signal A becomes I
OL= n X X 4 = n, A1 oH=
It has a driving capacity of m X X 4 = m waA.

Therefore, the output of the decoder 5 can control the driving ability of the output buffer.

〔Effect of the invention〕

As explained above, the present invention makes it possible to vary the drive capacity of the output buffer, and when using an LSI tester, it is possible to prevent malfunctions due to noise etc. even in a test pattern in which the output signals of multiple pins change simultaneously.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention.

Claims (1)

[Claims] a totem pole output buffer that supplies the output current;
A semiconductor integrated circuit comprising: a state output buffer; and a decoder that outputs a signal for controlling the three-state output buffer.