Application scheme | application of Sichuan earth microelectronics ca-is398x in PLC field

With 《 Made in China 2025》 Planning and “ Industry 4.0” The launch of the strategy , Industrial intelligence and digitalization in industrial control （ Such as PLC、 Industrial data acquisition 、CNC Control, etc. ） The position of the field is becoming more and more important . In this paper, industry PLC For example , Share Sichuan earth microelectronics CA-IS398X Application case of digital input receiver .

PLC It is a programmable controller , It uses programmable memory to store , Perform an operation 、 Sequence control 、 Timing counting and other operation instructions , And through digital 、 Analog input and output , Control various types of machinery or production processes . It can also work with other computers 、 Man machine interface , Or cloud communication networking , Realize information interaction .

from PLC As can be seen from the block diagram , It contains controllers and enclosures 、 Analog quantity 、 Digital input and output module 、 Communication module 、 Power supply module, etc .

This article will focus on the digital input module , This paper focuses on the basic requirements of the module design and the evolution of the scheme . From the traditional discrete scheme of rectifier bridge and optocoupler , An integrated solution evolved into an isolated digital input receiver .

as everyone knows , The digital input module shall have two basic functions ： Input signal conditioning and signal isolation .

About input signal conditioning ： As shown in the figure above ,IEC61131-2 Three types of digital inputs are specified Type1,2,3.Type1 The signal contains a two-wire relay 、 Button 、 switch （Relay, Button, Switch） etc. .Type2、Type 3 The signal contains sensors 、 Proximity switches, etc , among ,type3 Lower power . For the above types of signals , Through the partial voltage resistor , Adjust the amplitude of the signal . In addition, this part of signals measured on site may be source type 、 Leaky or hybrid output , The rectifier bridge is required to adjust the signal into a unidirectional DC signal .

About signal isolation ： Isolation is used to meet the requirements of safety regulations or reduce the noise of grounding loop . There are generally three methods for signal isolation ： Capacitive isolation 、 Optocoupler isolation and magnetic isolation . Capacitive isolation has higher reliability than optocoupler and magnetic isolation technology , Reflected in long service life 、 High withstand voltage and common mode transient rejection ratio , At the same time, it has less electromagnetic radiation 、 Low transmission delay and low power consumption . stay PLC It has great advantages in application scenarios .

Chuantu microelectronics CA-IS398X 8 Channel isolated digital input receiver series products , Integrated rectifier circuit and capacitive isolation circuit , It can be used as a perfect substitute for diode rectification and optocoupler isolation .

The product has the following features ：

1、 Single chip integration 8 Channels , It greatly saves the power consumption and PCB Cloth plate area ;

2、 Integrated rectifier bridge and signal conditioning , It can support relays from the field side 、 switch 、 Button, etc 、 Negative voltage signal ;

3、 Adopt the containment scheme , Inherit all the advantages of capacitive isolation ;

4、 Optional tape SPI chip , Connected by daisy chain , The controller only needs one circuit SPI Interface , It can receive multiple digital input signals ;

5、 Adjustable debounce filter , The best de jitter effect can be configured for different field side input signals .