![]() The minimum interaction between the gold film and the polyimide film, coupled with high temperature stability of the polyimide film, results in a system that provides reliable insulation when subjected to various types of environmental stresses.įigure 2. The polyimide layers have good mechanical elongation and tensile strength, which also helps the adhesion between the polyimide layers or between polyimide layer and deposited metal layer. The top coil is gold plated, with a 4 μm thick layer, and the coil track width and spacing between the turns are all 4 μm. Because of the structural quality of these wafer processed polyimide films, no partial discharge over 5 pC can be detected, even at 3 kVRMS. This provides a comfortable margin over the production test voltage of 3 kVRMS. The breakdown strength of the cured polyimide film is greater than 300 V/μm, so 20 m of polyimide provides greater than 6 kV of insulation between a given transformer’s coils. Some primary characteristics of this polyimide are shown in Table 1. The polyimide between the top and bottom coils is about 20 mm thick. ![]() The driver die is a standard CMOS chip, and the receiver die, shown in Figure 2, is a CMOS chip with the additional structures of two polyimide layers and transformer primary coil fabricated on top of the passivation. The driver chip sitting on the left paddle takes the input digital signal, encodes it, and drives the encoded differential signal through bond wires to the top coils of the transformers built on top of the receiver chip sitting on the right paddle. Cross-sectional view of top coil and polyimide layers. Cross-sectional view of ADuM1100 in an 8-lead SOIC package Figure 1b. The molding compound has breakdown strength over 25 kV/mm, so the 0.4 mm gap filled with molding compound provides greater than 10 kV insulation between the substrates of two IC chips.įigure 1a. There are two lead frame paddles inside the package, with gap between them of about 0.4 mm. A cross-section view of the ADuM1100 is shown in Figure 1. It has two ICs packaged in an 8-lead SOIC package. ![]() The ADuM1100 is a single-channel 100 Mbps digital isolator. ADuM1100 Architecture: A Single-Channel Digital Isolator The combination of high bandwidth for these on-chip transformers and fine scale CMOS circuitry leads to isolators of unmatched performance characteristics in power, speed, timing accuracy, and ease of use. The bidirectional nature of inductive coupling further facilitates bidirectional signal transfer. iCoupler isolated transformers can be monolithically integrated with standard silicon ICs and can be fabricated in single- or multichannel configurations. iCoupler technology leverages thick-film processing techniques to build microscale on-chip transformers and achieves thousands of volts of isolation on a chip. The first product, the ADuM1100 single-channel digital isolator, is in volume production. Recently iCoupler ®, a new isolation technology based on chip scale transformers, was developed by Analog Devices. ![]() ![]() All these isolators are restricted, moreover, because of integrated circuit integration limitations and the fact that they often need hybrid packaging. The capacitively coupled isolators have limitations in their size and ability to reject common-mode voltage transients, while the traditional transformer assembly based isolators are bulky and expensive. The intrinsic low conversion efficiencies for electrical light conversion and slow response photo detectors lead to optocoupler limitations in terms of lifetime, speed, and power assumption. Optocouplers rely on light emitting diodes to convert the electrical signals to light signals and on photo detectors to convert the light signals back to electrical signals. There are three commonly known classes of isolation devices: optocouplers, capacitively coupled isolators, and transformer based isolators. To maintain safety voltage at the user interface and to prevent transients from being transmitted from the sources, galvanic isolation is required. The controller then needs to transmit commands as a result of the analysis performed, coupled with user inputs to various actuators, to achieve certain operations. In many industrial applications, such as process control systems or data acquisition and control systems, digital signals must be transmitted from various sensors to a central controller for processing and analysis. High Speed Digital Isolators Using Microscale On-Chip Transformers ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |