Isolated Digital Input knowledge

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/ 2019-07-01 / Tech

Although isolated digital inputs and digital isolators sound similar, there are some significant differences between them. After reading this blog post, I hope you can easily distinguish the difference between the two isolation features.

 

Internal Structure

 

The Digital Isolator acts as a galvanically isolated digital signal The basic (or usually enhanced) functionality of the path. The isolation structure from Texas Instruments is capacitive and its insulating barrier consists of two high voltage capacitors built with our complementary metal oxide semiconductor (CMOS) process technology. The high frequency carrier communicates from the primary side to the secondary side through the isolation barrier, and our digital isolators are capable of withstanding surge voltages up to 12.8 kV and operating voltages of 1.5 kV without damaging the dual capacitance barrier. A key component of digital isolators is the basic or reinforced isolation voltage.

 

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Figure 1: Digital Isolator

 

Isolated Digital Input Acts Provides basic functionality for galvanic isolation from sensor inputs or other input types to the logic output of the host controller interface. Unlike digital isolators, the input stage of the isolated digital input (shown in Figure 2) includes user-set input thresholds and integrated currents. limit,Allows input voltages ranging from 9V to 60V to be converted to logic outputs. In its simplest form, the isolated digital input acts as an isolated comparator with some additional features that are easy to design.

 

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Figure 2: Isolated Digital Input

 

Usage differences

 

Digital isolators are typically used for analog-to-digital converters (ADCs) in signal paths or Between the data acquisition converter and the host controller or microcontroller (MCU). Digital isolators are also common in the isolated power functions of a given system.

 

Isolated digital inputs are specifically designed as digital input receivers for programmable logic control (PLC), motor control, and grid applications for field-side inputs and host The interface between the controllers. Isolated digital inputs are field-oriented inputs that can be easily configured for sink and source applications. The integrated current limit minimizes input heat distribution at higher input voltages and is easily externally configurable to comply with International Electrotechnical Commission (IEC) 61131-2 Type I, II or III switches. An additional resistor sets the input voltage threshold; the resistor can be easily selected using the online calculator.

 

Power Differences

 

The digital isolator requires primary and secondary side power supplies. In Figure 3, the isolated power supply supplies the "field side" of the ADC and the digital isolator connected to the ADC.

 

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Figure 3:ISO7741 isolated MCU and ADC communication

 

Isolated digital input only requires secondary side power supply. In the ISO1211 (Figure 4) and ISO1212 isolated digital inputs, the field side is powered by the input, so no field side power is required. This solution is easier to design for the front end than other discrete solutions.

 

Our new isolated digital input is an example of TI's many innovative ways. TI is making the world's most powerful The most reliable isolation solution is easier and more efficient.

 

 

 


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