JPS59125653A - Analog multiplexer ic - Google Patents

Abstract

PURPOSE:To obtain high S/N ratio by disposing the position of a bonding pad at an input terminal of an analog switch inside from an output signal line as seen from the side of a chip, thereby inhibiting to cross the wiring to the analog switch and the output signal line. CONSTITUTION:Wirings from a drive circuit 3 to an analog switch 2 are formed through a switch array, and since bonding wires 6 cross an output signal line 4, the wiring to the gate of an analog switch FET8 from the circuit 3 and the line 4 do not cross at all. The capacity between the bonding wire 6 and the line 4 becomes much smaller than that between the lines occurred via multilayer wirings by the interlayer insulating films, the capacity component which contributes to the noise does not exist difference from the capacity between the electrodes of an FET itself, but most of the noise can be removed. A bonding pad 5 is displaced to the inside merely by the amount for passing the line 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an analog multiplexer IC used for selectively outputting a plurality of analog signals.

The range of applications of analog switches that electronically turn analog signals on and off (ON-OFF) is rapidly expanding with the development of electronic circuit technology and the spread of digital technology. The most notable example is the analog signal converter of computer-controlled automatic circuits, and recently, as will be described later, it has also been widely used as a switching element for line sensors. In this way, from now on there will be many applications for switching a large number of analog signals, and an analog switch array that includes an analog switch array and drive circuits such as address decoders and shift registers to select and switch all of them in one IC. It seems that multiplexer TC will play a central role. From a performance standpoint, it is desired that a smaller signal be used to switch the pot speed.

FIG. 1 shows an example of a chip configuration of an analog multiplexer IC. In the figure, 1 is silicon.

2 is an analog switch section, 3 is a drive circuit section, 4 is an output signal line, 5 is a bonding pad on the chip, 6 is a bonding wire, and 7 is an IC bin. The configuration shown in Figure 1 is a common one for this god.
In particular, the bonding panode 5 is usually placed at the periphery of the chip.

However, as long as the chip configuration is like this, the S/N ratio of the analog switch will be very poor as described below.

In order to clarify the cause of this small S/N ratio, Figure 1 is rewritten as Figure 2.6 In Figure 2, 8 &:I
, the most common FET as an analog switch, 9 is F
It represents the interline valley k caused by the intersection of the wiring to the gate of Jy'r and the output signal line. As can be seen from Figure 1, from the drive circuit 3 to the analog switch 2
Although the wiring for sending control signals to the terminal is not shown, it always intersects with the signal line on the input side or the output side. Therefore, the second
As shown in the figure, a line m1 capacitance is generated. This line capacitance is FT! It is known from noise analysis of two-dimensional MO8 type sensors that the switching pulse for switching the XT is fed through to the output line III, causing switching noise 4 to enter the output line side.

This can be explained by converting the linear sensor into an analog multiplexer I.
Let us briefly describe the case of scanning with C as an example. Third
The figure is that episode i? This is an example of 64ft J. In the figure 1
0 is a power supply, 11 is a photodiode, 12 is an analog multiplexer IC, 1 and 3 are 1='E 'I'.

14 HFET electrode valley B::,] 5 is the distance between the wiring to the gate and the output signal line, 1
6 is a load resistance. jiij work is general storage 41゛i
Do it in the same way as the -1-sensor of the mold. FIG. 4 shows the gate pulse φG, noise, and optical signal. In the figure, A is the feedthrough of the Kate pulse due to the line capacity 'Nl''15,
The surface 1 question and answer amount 15 and the load resistance 16 form a differential circuit of the form Jjy,
Therefore, it is in the form of a differential pulse. f3 is times 4'-
Noise IQ due to feedthrough due to IK tunnel capacitance 14
The difference in constant is due to the difference in capacitance size.

Since the capacitance h4- differs depending on how the IC is manufactured, the inter-wiring capacitance is considerably larger than the inter-electrode capacitance 14.

C represents an optical signal. Output voltage V in Figure 3
oαt is the sum of A, B, and C/ζa). It is reasonable to view a storage type signal in terms of the amount of charge, and most of the noise charge is due to line capacitance.

Comparing the loudness of the sound of the light and the sound of the god sensor, the sound is often louder.
In an example in which switching was performed using a 6-bit analog multiplexer IC, the average noise was about 10 times as large as the optical signal, and the variation was about the same as that of the optical signal in the bright state. The situation with a two-dimensional MO8-type seven-sensor sensor is even more severe, and it is said that if no countermeasures are taken against switching noise, the noise can reach 10' times the signal. In the future, an analog multiplexer will be used for switching the minute signals of this glaze.
Reducing the above-mentioned noise is a very serious problem in the application of C.

It is an object of the present invention to eliminate the drawbacks of conventional analog multiplexer ICs, and to provide an analog multiplexer IC with a high S/N ratio without increasing the manufacturing process compared to conventional ICs.
Our goal is to provide the following.

In the analog multiplexer IC, the bonding panoply of the input end of the analog switch is placed from the periphery of the chip to the inside of the output signal line, so that the input end of the analog switch and the focus of the IC The bonding wiring Aj+' is performed over the output signal supply, and the wiring from the drive circuit to the analog switch and the output signal line do not intersect. FIG. 5 shows a four-piece structure of the present invention, which is similar to FIG. 2 which shows the conventional structure. The components themselves are the same as the conventional ones. Analog multiplexer IC of the present invention
As is clear from Fig. 5, since the bonding wire is located near the output (II'i factory), the opening from the drive section 3 to the gate of each analog switch L"ET and the output signal gloss "4" Therefore, the capacitance between the bonding wire and output line 8 is much smaller than the line capacitance 'i' caused by multi-layered grain distribution due to the interlayer insulating film. Therefore, the capacitance component that contributes to the higher noise caused by the conventional type is F
g Except for 'i11 of T itself and the amount of questions and answers, it does not exist at all. 11j As mentioned above, the line capacitance is higher than that of PET.
It is possible to eliminate most of the noise by the present invention, which is considerably larger than the interelectrode capacitance. Some conventional analog multiplexer ICs have long output signal lines routed through the drive circuit;
In c, the switching noise of the FET in the drive circuit rii is also added to the output. This is because the application of multiplexing small signals is not considered.
It is completely useless for this type of use, which will increase in the future. Compared to these ICs, the present invention has a tremendous effect on small signals.

An example of an embodiment of the analog multiplexer IC of the present invention is shown in FIG. The components are exactly the same as shown in FIG. Therefore, there is no increase in process or number of parts by implementing the present invention. In this case, the wiring from the drive circuit 3 to the analog switch 2 is easily routed between the two divided analog switch arrays, and does not cross the output signal line 4 at all. Furthermore, since the bonding panode is only i5, which is located as far inward as the output signal line passes, there is almost no problem with bonding.

As is clear from the above description, according to the present invention, an analog multiplexer IC having a S/N ratio of Sho i can be obtained without making any changes to the manufacturing process.

[Brief explanation of the drawing]

Fig. 1 is a layout diagram of the components of a conventional analog multiplexer IC, Fig. 2 is a diagram for explaining the components of the conventional analog multiplexer IC, and Fig. 3 is a diagram for explaining the components of the conventional analog multiplexer IC. Application of a conventional analog multiplexer to the sensor L7/ position lit
FIG. 6 is a diagram showing an example of an embodiment of the present invention. In the figure, 1... Silicon chip 2... Analog switch section 3... Drive circuit section 4... Output signal button Tτ5.
・Bonding panode 6...Bonting wire 7
...IC pin 8...Fr (T9...
Between the lines fi: j' 10... City Ryo] 1...
Photodiode 12...Analog multiplexer IC ＼----,ノ'g 4 Figure

Claims (1)

[Claims] An analog multiplexer IC consisting of an analog switch array and a drive circuit for driving the same, in which bonding wiring between the input terminals of the analog switches on each side and the bin of the IC is performed over the output signal line. Become,
An analog multiplexer IC characterized in that the wiring from the drive circuit to the analog switch is arranged so as not to intersect with the output signal line.