According to one embodiment, a digital isolator includes a first metal portion, a first insulating portion, a second metal portion, a third metal portion, and a first layer. The first insulating portion is provided on the first metal portion. The second metal portion is provided on the first insulating portion. The third metal portion includes first, second, and third portions. The first portion is provided around the first metal portion in a direction perpendicular to a first direction. The second portion is provided on a portion of the first portion with a first conductive layer interposed. The third portion is provided on the second portion and provided around the second metal portion in the perpendicular direction. The first layer contacts the first conductive layer and an other portion of the first portion and is provided around a bottom portion of the second portion.

A self-oscillating spread spectrum frequency control loop contains a gated voltage-controlled oscillator (VCO) which receives a digital signal that can start or stop its oscillation. The VCO generates a spread spectrum carrier by receiving a triangle wave signal from a delaying ramp generator in a loop, its ramp direction controlled by a frequency comparator. The loop generates a spectrum spread as wide as possible above a minimum frequency. RF isolators that utilize low-pass filters in the transmitter and high-pass filters in the receiver, where the F-3 dB cutoff frequencies of both filters vary in a correlated manner, are used to not produce spread spectrum frequencies below the minimum frequency. Die from a given wafer lot, when designed such that the low- and high-pass cutoff frequencies track, can be used to form RF digital isolators whose minimum spread spectrum frequency does not go below the minimum frequency required by that wafer lot.

According to one embodiment, a digital isolator includes a first metal portion, a first insulating portion, a second metal portion, a third metal portion, and a first layer. The first insulating portion is provided on the first metal portion. The second metal portion is provided on the first insulating portion. The third metal portion includes first, second, and third portions. The first portion is provided around the first metal portion in a direction perpendicular to a first direction. The second portion is provided on a portion of the first portion with a first conductive layer interposed. The third portion is provided on the second portion and provided around the second metal portion in the perpendicular direction. The first layer contacts the first conductive layer and an other portion of the first portion and is provided around a bottom portion of the second portion.

Several circuits and methods for transferring an input data signal in a digital isolator are disclosed. In an embodiment, the digital isolator includes an isolation element, input circuit, and output circuit. The isolation element includes at least one input node and at least one output node, the input circuit is electronically coupled to the input node and generates modulated differential data signals based on modulating the input data signal on a carrier signal. The input circuit operates using a first supply voltage with respect to a first ground. The output circuit is electronically coupled to the output node to receive the modulated differential data signals, operates using a second supply voltage with respect to a second ground and includes a frequency-shift keying demodulator configured to generate a demodulated data signal in response to detection of presence of the carrier signal. The output circuit further generates an output data signal.

According to one embodiment, a digital isolator includes a first metal portion, a first insulating portion, a second metal portion, a third metal portion, and a first layer. The first insulating portion is provided on the first metal portion. The second metal portion is provided on the first insulating portion. The third metal portion includes first, second, and third portions. The first portion is provided around the first metal portion in a direction perpendicular to a first direction. The second portion is provided on a portion of the first portion with a first conductive layer interposed. The third portion is provided on the second portion and provided around the second metal portion in the perpendicular direction. The first layer contacts the first conductive layer and an other portion of the first portion and is provided around a bottom portion of the second portion.

In an example, a system includes circuitry on a first side of an isolation barrier and circuitry on a second side of the isolation barrier, where the isolation barrier is operable to electrically isolate the first side from the second side. The system also includes a trimmed oscillator, a first transmitter, and a first receiver on the first side, the trimmed oscillator coupled to the first transmitter. The system includes a tunable oscillator, a second transmitter, and a second receiver on the second side, the tunable oscillator coupled to the second receiver and the second transmitter. In the system, the first side is configured to transmit a training sequence to the second side, and the second side is configured to tune the tunable oscillator based on the training sequence.

A self-oscillating spread spectrum frequency control loop contains a gated voltage-controlled oscillator (VCO) which receives a digital signal that can start or stop its oscillation. The VCO generates a spread spectrum carrier by receiving a triangle wave signal from a delaying ramp generator in a loop, its ramp direction controlled by a frequency comparator. The loop generates a spectrum spread as wide as possible above a minimum frequency. RF isolators that utilize low-pass filters in the transmitter and high-pass filters in the receiver, where the F-3 dB cutoff frequencies of both filters vary in a correlated manner, are used to not produce spread spectrum frequencies below the minimum frequency. Die from a given wafer lot, when designed such that the low- and high-pass cutoff frequencies track, can be used to form RF digital isolators whose minimum spread spectrum frequency does not go below the minimum frequency required by that wafer lot.

Methods, systems, and apparatus to increase common-mode transient immunity in isolation devices is disclosed. An example apparatus includes a current mirror including an input terminal and an output terminal; a transistor including a gate terminal, a first current terminal, and a second current terminal, the gate terminal coupled to a reference voltage terminal, the first current terminal coupled to the input terminal of the current mirror, and the second current terminal coupled to an input node; a buffer including an input terminal and an output terminal, the input terminal of the buffer coupled to the output terminal of the current mirror; and a logic gate including an input terminal and an output terminal, the input terminal of the logic gate coupled to the output terminal of the buffer.

Various examples are directed to isolated analog-to-digital converter (ADC) circuits comprising a first side that is separated from a second side by an isolator. A first ADC positioned on the first side may be configured to convert a first analog input signal to a first side multi-bit digital signal. A digital modulator on the first side may be configured to convert the first side multi-bit digital signal to a first single-bit stream. A first filter positioned on the second side may be configured to receive the first single-bit stream across the first isolator and to generate a first reconstructed multi-bit digital signal using the first single -bit stream.

A method of detecting crosstalk for a digital isolator having first and second channels including two die with channels including a transmit side, receive side, with 1 die including a capacitive barrier for each channel. A first clock signal at a first frequency in a first pulse pattern and a second clock signal at a second frequency in a second pulse pattern are configured, wherein the pulse patterns have a phase difference. The transmit side of the channels each encode their received clock pulse pattern, then modulate with a carrier frequency to provide a fc1 and a fc2 signal, respectively. The receive side of the channels demodulate received signals during a rising or falling edge of their clock signal to generate a delayed received version of the first and second clock pulse pattern. Missing pulses are identified by comparing the delayed received clock pulse patterns to their clock pulse patterns.