Logic isolator with high transient immunity
First Claim
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1. A logic isolator for isolating digital logic signals, the isolator comprising:
- a transmit circuit for receiving a digital logic signal with rising and falling edges, the transmit circuit having edge detection circuitry for providing pulses that indicate relative locations in time of the rising and falling edges, the transmit circuit providing these pulses as a transmit output signal;
a transformer assembly including;
a first core,a first winding wrapped around the first core for receiving the transmit output signal,a second core,a second winding wrapped around the second core for providing a transformer output signal that is substantially similar to the transmit output signal, anda grounded link wire extending through the first core and the second core for grounding common mode transient signals received from the first winding of the transformer assembly; and
a receive circuit for receiving the transformer output signal, and including circuitry for converting pulses in the transformer output signal into an isolated output signal with rising and falling edges at substantially the same relative locations as the rising and falling edges in the digital logic signal.
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Abstract
A logic isolation circuit with high transient immunity has a link-coupled transformer assembly for providing isolation. An input circuit provides pulses that indicate rising and falling edges, and an output circuit on the isolated side of the barrier converts the signal with pulses back into a digital logic signal with rising and falling edges. An interrogation feature allows the output to be updated frequently. The logic isolator can be provided in a single module for use in a process control board, or it can be provided as multiple parts for mounting on a circuit board.
260 Citations
30 Claims
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1. A logic isolator for isolating digital logic signals, the isolator comprising:
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a transmit circuit for receiving a digital logic signal with rising and falling edges, the transmit circuit having edge detection circuitry for providing pulses that indicate relative locations in time of the rising and falling edges, the transmit circuit providing these pulses as a transmit output signal; a transformer assembly including; a first core, a first winding wrapped around the first core for receiving the transmit output signal, a second core, a second winding wrapped around the second core for providing a transformer output signal that is substantially similar to the transmit output signal, and a grounded link wire extending through the first core and the second core for grounding common mode transient signals received from the first winding of the transformer assembly; and a receive circuit for receiving the transformer output signal, and including circuitry for converting pulses in the transformer output signal into an isolated output signal with rising and falling edges at substantially the same relative locations as the rising and falling edges in the digital logic signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A logic isolator for isolating digital logic signals comprising:
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an input circuit for detecting rising and falling edges in an input digital logic signal, and for providing an output signal indicative of relative locations of the rising and falling edges; a transformer assembly with a shielded single transformer for receiving the output signal from the input circuit and for providing a signal similar to the signal received by the transformer; and an output signal circuit for receiving the signal from the transformer and for providing an output signal with rising and falling edges in the same relative locations as the rising and falling edges in the input digital logic signal. - View Dependent Claims (14, 15, 16, 17)
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18. A method for logically isolating a digital logic signal comprising:
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providing to a first side of an isolation barrier edge pulses indicative of rising and falling edges in a digital logic signal; periodically generating refresh pulses with a pulse width equal to a pulse width of the edge pulses, the refresh pulses indicating a DC level of the digital logic signal; providing the refresh pulses to the first side of the isolation barrier; receiving a signal with edge pulses and refresh pulses on a second side of the isolation barrier; and converting the received signal to an output digital logic signal that indicates relative locations of rising and falling edges in the digital logic signal. - View Dependent Claims (19, 20, 21, 22)
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23. A digital logic isolator comprising:
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a transmit circuit for receiving an input digital logic signal and including edge detection circuitry for converting rising and falling edges of the input digital logic signal into edge pulses having a pulse width, the transmit circuit providing a transmit output signal with the edge pulses; a pulse generator for providing refresh pulses at a desired frequency, the refresh pulses indicating a DC level of the input digital logic signal; an isolation barrier for receiving the edge pulses and the refresh pulses and for providing an isolated output signal with the edge pulses and the refresh pulses; and a receive circuit for receiving the isolated output signal and for using the edge pulses to produce an output digital logic signal with rising and falling edges at relative locations that are the same as the rising and falling edges in the input digital logic signal. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30)
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Specification