![]() Insulating material in many digital isolators for a number of reasons, includingĮxcellent breakdown strength, thermal and mechanical stability, chemical resistance, ESD performance, and relatively low permittivity. ![]() Polyimide is a polymer composed of imide monomers. Polyimide Film Applications for Digital Isolators (a) A digital isolator in a plastic package and (b) a transformer cross-section. (a) An optocoupler schematic and (b) an optocoupler package cross-section.įigure 2. We will review the detailedĬonstruction of these isolators, deposition methods for these polyimide films,Ĭharacterization of the polyimide films, high voltage performance, and agingįigure 1. For the transformer-based digital isolators shown in Figure 2, isolation performance is mainly limitedīy 20 μm to 40 μm thick polyimide layers sandwiched between the top andīottom coils of the chip scale microtransformers. The optocouplers shown in Figure 1 rely on a few mm thick molding compoundīetween the LED die and photodiode die to achieve isolation. Is orders of magnitude lower than those of optocouplers. Well over 10 for these transformers, the power consumption for these digital isolators Used to realize digital isolators from 150 Mbps to 600 Mbps. Have a self-resonant frequency from a few hundred MHz to a few GHz and they can be High reliability for these digital isolators based on transformers. Transfer ratio for the optocouplers, it does not degrade over time, which leads to the Spiral and bottom spiral depends only on the size and separation. With little interference between the channels. This enables multiple channel integration Little coupling between spirals side by side. Provide tight magnetic coupling between the top coil and bottom coil, and very The stacked spirals used in digital isolators Isolators using microtransformers 1,2 allow for the integration of multiple transformersĪnd other necessary circuit functions. Needs for demanding applications such as automotive.ĭigital isolators remove the penalties associated with isolation and they provideĬompelling advantages over optocouplers in terms of high speed, low powerĬonsumption, high reliability, small size, high integration, and ease of use. As the current transfer ratio for optocouplersĭegrades over time, especially at high temperatures, it fails to meet the reliability ![]() Overall system power budget in power limited industry systems such as processĬontrol 4 mA to 20 mA systems. Their high power consumption due to their LED puts a significant constraint on the Speed requirements for many isolated field bus communications such as RS-485 Propagation delay present significant challenges in meeting the ever-increasing High power consumption, and limited reliability. Isolation for decades, they present significant limitations in terms of low speed, Loops that affect data acquisition accuracy. ![]() Isolation can also eliminate common-mode noises or ground Present on the field side, where more robust components such as sensors andĪctuators reside. For example, isolation protects sensitive circuit components and human interface on the system side from dangerous voltage levels Isolation between circuit components is typically required for safety and/or data Structural improvements to improve polyimide high voltage lifetime will Polyimide agingīehavior under various high voltage waveforms such as ac or dc was studied,Īnd isolator working voltage is extrapolated through a polyimide lifetime Isolators need to satisfy various high voltage performances, such as shortĭuration withstand voltage, surge voltage, and working voltage. To meet various safety standards such as UL and VDE, digital In thisĪrticle, digital isolator construction using polyimide films as isolation layers Winding and bottom spiral winding for the stacked winding transformers. What are essential for the high voltage performance of theseĭigital isolators are polyimide films deposited in between the top spiral Widely adopted in many markets, including automotive, industry automation, Billions of digital isolators using microtransformers have been Of high speed, low power consumption, high reliability, small size, high integration,Īnd ease of use. Polyimide Film Uses for Digital Isolatorsĭigital isolators provide compelling benefits over legacy optocouplers in terms
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