Crosstalk reduction in receiver inductive loop using capturing loop in transmitting inductive loop

Abstract

An inductively coupled multi-channel digital isolator where the transmitter and receiver inductive loops of a given channel are coplanar. In the case where two adjacent channels flow data in opposite directions, the receiver inductive loops of a given channel include a large, generally conventional loop portion and a small loop portion that is located inside the transmitter inductive loops of the adjacent channels. The sizes of the small loop portion and the conventional loop portion are generally in the ratio of the magnetic flux in the conventional loop portion to the magnetic flux in the transmitter inductive loop. This size relationship results in the voltage of the small loop portion being very close but opposite in sign to the voltage in the conventional loop portion. As a result, there is minimal crosstalk from the transmitter inductive loop of one channel to the receiver inductive loop of the adjacent channel.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This continuation application claims priority to U.S. patent application Ser. No. 16 / 021,175, filed Jun. 28, 2018, which application is hereby incorporated herein by reference in its entirety.BACKGROUND1. Field[0002]The field is digital isolators.2. Description of the Related Art[0003]Digital isolators are used to allow signal transfer between environments that must remain electrically isolated. The simplest form of a digital isolator is an opto-coupler. In an opto-coupler a signal is provided to drive a photodiode. A phototransistor is configured to receive the light emitted from the photodiode. Electrical isolation is provided between the photodiode and the phototransistor simply by an air gap through which the light passes. However, there are many circumstances where opto-couplers do not provide adequate performance. Therefore, another class of digital isolators has developed which utilize a capacitive isolation barrier. Effectively on...

AI Technical Summary

Benefits of technology

[0005]In an inductively coupled multi-channel digital isolator the transmitter and receiver inductive loops of a given channel are coplanar. In the case where two adjacent channels flow data in opposite directions, the receiver inductive loops of a given channel include a large, generally conventional loop portion and a small loop portion that is located inside the transmitter inductive loops of the adjacent channels. The sizes of the small loop portion and the conventional loop portion are generally in the ratio of the magnetic flux in the conventional loop portion to the magnetic flux in the transmitter inductive loop. This size relationship results in the voltage of the small loop portion being very close but opposite in sign to the voltage in the conventional loop portion. As a result, there is minimal crosstalk from the transmitter inductive loop of one channel to the receiver inductive loop of the adjacent channel. This allows a more densely packed and coplanar arrangement of the inductive loops, making manufacturing more cost effective.

Problems solved by technology

However, there are many circumstances where opto-couplers do not provide adequate performance.

However, modern ultralow power requirements have made even the lower power levels of capacitive isolation digital isolators insufficient in many instances.

While this is not an issue for capacitive isolation digital isolators, this bi-directional configuration results in the potential for undesired crosstalk or cross-coupling in an inductive loop or transformer digital isolator.

Another approach stacks the receive and transmit inductive loops vertically, but this makes manufacturing much more challenging.

Images