JPH022710A - Noise reduction circuit - Google Patents

Abstract

PURPOSE:To eliminate the cause of malfunction by suppressing a through current and also, suppressing voltage fluctuation. CONSTITUTION:When the source voltage of a buffer FET4 is increased by the through current, a current control FET5 is turned on, and a path with a state where resistance is interposed between a P buffer FET3 in a NOR circuit which supplies a gate voltage to the FET4 is formed, and the voltage between the gate and the source of the FET4 drops. Thereby, the current on the FET4, and also, the voltage fluctuation can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a noise reduction circuit that reduces internal noise in IC design.

[Conventional technology]

Figure 2 is a circuit diagram of a conventional output circuit.
), (2) are data signal and output control signal terminals, respectively, (3) is a buffer 1 transistor for 1H level output,
(4) is a buffer transistor for 1L level output. These circuits have the number of output pins (6).
1) is connected between the source pad (7) and the GND pad (8a).

Next, the operation will be explained. The data amplified by the sense amplifier turns on one of the output buffer transistors (3) and (4) and turns the other one off in response to a signal from the input terminal (1) or (2).

This determines that the output data is 5H' or 1L'.

[Problem to be solved by the invention]

Since the conventional output circuit is configured as above, the output data is 1L' to 4) (#, or %H1 to %L).
’, step-down time (tf), step-up time (tr)
As expected, a through current flows through transistors (3) and (4).
The total through current increases as the number of output pins increases. Voltage fluctuations occur because the output circuit's ability to supply 9 currents is insufficient for the instantaneous current flowing, or because of instantaneous wiring resistance. This voltage fluctuation causes the apparent internal threshold value to change, causing a problem of malfunction.

This invention was made to solve the above-mentioned problem, and aims to suppress voltage fluctuations and eliminate causes of malfunction by controlling instantaneous through-current.

[Means to solve the problem]

The noise reduction circuit according to the present invention senses voltage fluctuations, controls the gate voltage of the output buffer transistor, and suppresses voltage fluctuations by controlling through current.

[Effect]

The through current control circuit according to the present invention starts operation by sensing minute voltage fluctuations, suppresses subsequent voltage fluctuations, and reduces noise.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, symbols (1) to (4) and ((3) to (8)
A) is the same as the conventional method and). (5) uses the source of the output buffer transistor (2) as a gate signal,
It is a 9-flow control transistor with the gate signal as the drain and another GND pad (8b) as the source.

Next, the operation will be explained. As explained in the conventional output circuit, the buffer transistor (4)
The source voltage of is momentarily raised.

If the current control transistor (5) is a low-threshold N-type transistor and is set to respond to a slight increase in gate voltage, the current control transistor (5) will When it is turned on, a path is created via a resistor between the Pi buffer transistor (3) of the NOR circuit that supplies the gate voltage of the buffer transistor (4), and the 0 point in Fig. 2 is the transistor (3). 9), α0, and the resistance ratio of (5) causes the voltage to drop below the normal voltage level of the power supply.This means that the voltage between the gate and source of the buffer transistor (4) drops, suppressing the current in the buffer transistor (4). It also suppresses the plow pressure fluctuation by 6% in the direction.

3 and 4 show the circuit and output waveforms used in the simulation of the circuit of the present invention. In this simulation, a coil component was used to simulate a rise in GND. The simulation results shown in Figure 4 also show that fluctuations in normal pressure can be suppressed by this means.

〔Effect of the invention〕

As described above, according to the present invention, S'ff pressure fluctuations can be suppressed by means of sensing fluctuations in normal pressure, and noise accompanying the suppression of voltage fluctuations can be prevented and the noise margin can be increased.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an output circuit showing an embodiment of the present invention;
Fig. 2 is an explanatory circuit diagram showing the current path during operation of the present invention, Fig. 3 is a circuit diagram used for simulating the circuit of Fig. 1, and Fig. 4 shows the through current obtained by the simulation. The waveform diagram in FIG. 5 is a circuit diagram of a conventional output circuit. In the figure, (1) and (2) are input signal and output control signal terminals, (3) is a P-type buffer transistor, and (4) is an N
type buffer transistor, (5) is a current control transistor, (6a) to (6n) are output pads, (7) is a power supply pad, (8a) and (8b) are GND pads, (91)
, Qd is a P-type transistor, α power is output data, υ is the output buffer gate of the conventional circuit ￥ α pressure, (to) is the output buffer gate of this invention and is the voltage, α4 is the GND level of the conventional circuit, (to) is The GND level of this invention is shown. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] Noise reduction circuit that suppresses through current that causes voltage fluctuations and also suppresses voltage fluctuations.