JPS6230418A - Analog multiplexer - Google Patents

Abstract

PURPOSE:To improve the electric insulating efficiency of an I/O stage and to attain high speed operation by forming an I/O separating circuit having plural contact relays, a high speed switching circuit having plural semiconductor analog switches and a control circuit. CONSTITUTION:The I/O separating circuit 10 is constituted of plural input terminals A1-An to which analog voltages are impressed from the external, plural contact relays D1-Dn, and so on. The high speed switching circuit 12 is constituted of plural input terminals E1-En connected to respective output terminals of the circuit 10 and plural semiconductor analog switches G1-Gn. In the switching operation of analog input voltages Vi (i=1-n) in the n system, all capacitors Ci connected to all input terminals Ai are simultaneously switched by all relays Di, then all input voltages Vi are applied to all output terminals Bi. Then, the analog switches Gi are successively turned on one by one and the voltages Vi are successively inputted to a gain amplifier 16. Consequently, the electric insulating efficiency of the I/O stage can be improved and high speed operation can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application This invention relates to an analog multiplexer used, for example, when supplying a plurality of analog inputs to one A/D converter in a time-sharing manner.

B6 Summary of the Invention This invention transmits multiple analog input voltages all at once to a subsequent stage via a human output dividing circuit using a voltage storage capacitor and a contact relay, and transfers the voltage to a high-speed switching circuit using a semiconductor analog switch. The configuration is such that it is selectively led out to a common output terminal, achieving both electrical isolation between the external circuit and the input stage and high-speed operation.

C1 Conventional technology Analog multiplexers are broadly divided into non-contact type types that switch multiple inputs using semiconductor analog switches such as FETs (field effect transistors), and contact type types that use contact relays to switch multiple inputs. be done.

D0 Problems to be Solved by the Invention In the non-contact type analog multiplexer, the switching speed of the analog switch is extremely fast, so the switching operation can be easily increased in speed. However, because the input and output stages are always connected via analog switches, it is not possible to provide high electrical insulation, and abnormally high voltages from external circuits can directly reach internal circuits and subsequent circuits (A/D converters, etc.). It is easy for failures caused by external factors to occur.

A contact type analog multiplexer has a configuration in which the input stage and output stage are completely separated by relay contacts, so electrical insulation is high and internal circuit failures due to external factors are less likely to occur. However, since the switching speed of contacts is much slower than that of semiconductor switches, high-speed multi-input switching cannot be performed.

By the way, in process controllers, etc., many analog signals collected from various target devices are converted into digital signals, but instead of using many A/D converters, many analog signals are converted into digital signals using an analog multiplexer. A common configuration is to switch the signal to one A/D converter and perform A/D conversion in a time-division manner.

In the above-mentioned applications, analog multiplexers are strongly required to operate at high speed, and electrical isolation from various external circuits is also important.

None of the conventional analog switches can satisfactorily meet these demands.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide an analog multiplexer that has high electrical insulation between input and output stages and is capable of high-speed operation.

Means for Solving the E0 Problem The analog multiplexer according to the present invention includes an input/output separation circuit, a high-speed switching circuit, and a control circuit. The input/output separation circuit includes a plurality of input terminals to which analog voltages are applied from the outside, a plurality of voltage storage capacitors corresponding to each of these input terminals, a plurality of output terminals, and a plurality of capacitors connected to the input terminal and the output terminal. It consists of a plurality of contact relays that are switched and connected to the output terminal. The high-speed switching circuit has a plurality of input terminals respectively connected to each output terminal of the input/output circuit, one common output terminal, and a plurality of input terminals respectively connected between each of these input terminals and the common output terminal. Consists of a semiconductor analog switch. The control circuit simultaneously drives each of the contact relays in the input/output separation circuit to switch and connect each of the capacitors from the input terminal to the output terminal at the same time, and then drives each of the analog switches in the high-speed switching circuit. Turn them on one by one in order.

Due to the F1 function, the external circuit and the internal circuit are well separated by the contact relay of the input/output separation circuit, and high insulation is obtained.

Although the switching speed of this contact relay is slow, since it switches only once per cycle of switching operation, the effect on the overall operating time is small. Sequential switching of a plurality of inputs is performed at high speed using the analog switch.

G. Embodiment FIG. 1 shows a data processing device to which an analog multiplexer according to the present invention is applied. In the figure, an analog multiplexer of the present invention is configured by an input/output separation circuit 10, a high-speed switching circuit 12, and a control circuit 14. The analog multiplexer of the present invention is switched and selected by the input/output separation circuit 10, and the analog signal is sent to the A/D converter 18 via the gain amplifier 16. The input and digitized signals are taken into a microprocessor 20 for data processing. The control circuit 14 operates in response to instructions from the processor 20 and synchronizes the switching operation of the multiplexer and the conversion operation of the A/D converter 18.

In the input/output separation circuit 10, Ai (i=1, 2
,...

n) is the n input terminal, Bil is the output terminal corresponding to the input terminal Ai, Ci is the input/output terminal ^i, the voltage storage capacitor corresponding to Bi, and Di is the capacitor Ci between the input terminal At and the output terminal old. This is a contact relay that switches and connects to the

N systems of analog input voltages Vi from the outside are respectively applied to the input terminals Ai. When the capacitor Ci is connected to the input terminal ^i by the relay Di, the capacitor Ci is charged and the input terminal vi is stored therein.

Relay Di is switched and capacitor Ci is connected to output terminal Bi.
, the stored input voltage Vi is connected to the output terminal Bi
appears in Regardless of the state of relay Di, input terminal A
Since i and the output end Bi are completely separated, the insulation between input and output is extremely high.

In the high-speed switching circuit 12, Ei is n input terminals, F is one common output terminal, and Gi is each input terminal Ei and a common output terminal F.
This is an FET analog switch that connects the two.

Note that one line of each input terminal Ei is directly connected to one line of the common output terminal F in common.

Each input terminal Ei is connected to each output terminal Bi of the input/output separation circuit 10, and the common output terminal i is connected to the input terminal of a gain amplifier 16 at the next stage.

As shown in the timing chart of FIG. 2, one cycle of the switching operation of the n systems of analog input terminals Vi is as follows.

From a state in which all capacitors Ci are connected to all input terminals At, all relays Di are switched at once to lead out all input terminals Vi to all output terminals Bi. In a typical relay, this switching takes about 1On+s.

Next, the analog switches Gi are turned on one by one, namely Gl, G2 . ..., Gn and turn on one by one, and the voltages Vi, V2 . ..., Yn are input to the gain amplifier 16 in order. The operating time for one analog switch Gi is about 100 μs, and for n analog switches Gi, it is nx too μS. Therefore, the switching operation time for one cycle is loa+s+
nX 100 μs.

In addition, in the case of the above-mentioned contact type analog multiplexer, it takes as much time as nX 10m5. Compared to this, the method of the present invention is much faster.

H9 Effects of the Invention As explained in detail above, the analog multiplexer according to the present invention has the same high insulation between input and output as the conventional contact type, and there is no possibility of failure of the internal circuit due to external factors. It's hard to do. Moreover, the operating speed is much faster than that of conventional contact type and close to that of conventional non-contact type.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a data processing device using an analog multiplexer according to an embodiment of the present invention, and FIG. 2 is a timing chart showing the operation of the same multiplexer. 10...Input/output separation circuit, At...input end, old...
・Output end, Ci...capacitor, Di...contact relay, 12...high speed switching circuit, Ei...input end, F
...Common output terminal, Gi...PET analog switch, 14...Control circuit.

Claims (1)

[Claims] (1) A plurality of input terminals to which an analog voltage is applied from the outside, a plurality of voltage storage capacitors and a plurality of output terminals corresponding to each of these input terminals, and a plurality of capacitors connected to the input terminal and the output terminal. an input/output separation circuit consisting of a plurality of contact relays that are switched and connected to; a plurality of input terminals connected to each output terminal of the input/output separation circuit, one common output terminal, and each of these input terminals; a high-speed switching circuit consisting of a plurality of semiconductor analog switches respectively connected between the input terminal and the common output terminal; driving each of the contact relays in the input/output separation circuit simultaneously to switch each of the capacitors from the input terminal to the common output terminal; An analog multiplexer comprising: a control circuit that switches and connects the output terminals all at once, and then turns on each of the analog switches in the high-speed switching circuit one by one in sequence.