Analog isolation system with digital communication across a capactive barrier

A method for conveying an analog signal from a transmitting circuit to a receiving circuit while electrically isolating the transmitting circuit from the receiving circuit, comprising:

• converting the analog signal to a synchronous digital signal;
• transferring the synchronous digital signal across a capacitive isolation barrier to provide an isolated digital signal;
• converting the isolated digital signal to an analog output signal;
• and
• recovering a clock signal on the receiving circuit side of the barrier, and synchronizing the isolated digital signal to the recovered clock signal.

A bidirectional isolation barrier for conveying analog data signals between a powered circuit and an isolated circuit while electrically isolating the powered circuit from the isolated circuit, the barrier comprising:

• a first isolation capacitor;
• a powered-side signal processing system comprising:
• a first synchronous analog-to-digital converter having an input connected to the powered circuit for receiving an analog data signal to be transmitted across the barrier in a first direction, and an output connected to a first side of the isolation capacitor for providing a synchronous digital signal to the isolation capacitor, and
• a first synchronous digital-to-analog converter having an input connected to said first side of the isolation capacitor for receiving synchronous digital signals therefrom when data signals are transmitted in a second direction from the isolated circuit to the powered circuit, and having an output connected to the powered circuit for providing analog signals thereto;
• an isolated-side signal processing system comprising:
• a second synchronous digital-to-analog converter having an input connected to a second side of the isolation capacitor for receiving a synchronous digital signal therefrom when the data signals are transmitted in said first direction, and having an output connected to the isolated circuit for providing a reconstructed analog data signal thereto, and
• a second synchronous analog-to-digital converter having an input connected to the isolated circuit for receiving an analog data signal to be transmitted across the barrier in said second direction to the powered circuit, and an output connected to the second side of the isolation capacitor for conveying a synchronous digital signal corresponding to said analog data signal to the isolation capacitor;
• and
• a clock recovery circuit having an input connected to the isolation capacitor for receiving the synchronous digital signal therefrom, the clock recovery circuit having a data output and a clock output, the clock output providing a recovered clock signal, and the data output providing a digital data signal that is synchronized with the recovered clock signal.

A method for transmitting an analog data signal across a capacitive isolation barrier, comprising:

• converting the analog signal to a digital data signal;
• combining the digital data signal with control information to form a digital encoded signal;
• driving the digital encoded signal across the capacitive isolation barrier;
• receiving an isolated encoded signal from the isolation barrier;
• recovering a clock signal from the isolated encoded signal;
• synchronizing the isolated encoded signal with the clock signal;
• separating the isolated encoded signal into an isolated digital data signal and isolated control information;
• and
• converting the isolated digital data signal into an isolated analog signal.

An isolation system for communicating analog signal information across an isolation barrier in digital format, comprising:

• an analog-to-digital converter with an input connected to an analog signal containing information to be communicated across the isolation barrier;
• an isolation barrier having an input coupled to a digital output of the analog-to-digital converter;
• a digital-to-analog converter having an input coupled to an output of the isolation barrier, the digital-to-analog converter providing an analog output signal;
• wherein the analog-to-digital converter and the digital-to-analog converter are synchronized to a common clock signal;
• and
• a clock recovery circuit having an input coupled to the output of the isolation barrier.