Digital modulation scheme for data transfer

1. An isolated analog-to-digital converter (ADC) circuit, comprising:

a first multi-bit ADC positioned on a first side of the isolated ADC circuit, the first multi-bit ADC configured to convert a first analog input signal to a first side multi-bit digital signal, wherein the first side is separated from a second side of the isolated ADC circuit by a first isolator;

a digital modulator on the first side, the digital modulator configured to convert the first side multi-bit digital signal to a first single-bit stream; and

a first filter positioned on the second side, the first filter 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.

2. The isolated ADC circuit of claim 1 , further comprising:

a first die comprising the first multi-bit ADC and the digital modulator; and

a second die comprising the first filter, wherein the first isolator provides a signal path between the first die and the second die.

3. The isolated ADC circuit of claim 2 , wherein the first die and the second die are part of a first package.

4. The isolated ADC circuit of claim 2 , further comprising:

a third die separated from the second die by a second isolator, the third die comprising:

a second ADC configured to generate a second multi-bit digital signal using a second analog input signal; and

a second digital modulator configured to generate a second single-bit stream using the second multi-bit digital signal, and wherein the second die further comprises a second filter configured to receive the second single-bit stream across the second isolator and to generate a second reconstructed multi-bit digital signal using the second single-bit stream.

5. The isolated ADC circuit of claim 1 , further comprising a decimator electrically coupled between the first multi-bit ADC and the digital modulator to generate a decimated multi-bit signal.

6. The isolated ADC circuit of claim 5 , further comprising a multiplexer electrically coupled to receive the first side multi-bit digital signal, the decimated multi-bit signal, and a multiplexer input, wherein an output of the multiplexer provides the first side multi-bit digital signal when the multiplexer input is provided a first value and provides the decimated multi-bit signal when the multiplexer input is provided a second value.

7. The isolated ADC circuit of claim 1 , further comprising:

a first modulator configured to generate a first modulated data signal based at least in part on a digital data signal and a digital carrier signal at a first carrier frequency, wherein the first carrier frequency is greater than a frequency of the first single-bit stream; and

an adder configured to add the first modulated data signal to the first single-bit stream.

8. The isolated ADC circuit of claim 7 , further comprising:

a second modulator configured to generate a second modulated data signal based at least in part on the digital data signal and a second digital carrier signal at a second carrier frequency, wherein the second carrier frequency is greater than the first carrier frequency, wherein the second carrier frequency is greater than the frequency of the first single-bit stream, and wherein the adder is also configured to add the second modulated data signal to the first single-bit stream; and

a first band pass filter positioned on the second side, the first band pass filter configured generate a first filtered signal around the first carrier frequency;

a first peak detector configured to generate a first peak signal based at least in part on the first filtered signal;

a second band pass filter positioned on the second side, the second band pass filter configured to generate a second filtered signal around the second carrier frequency;

a second peak detector configured to generate a second peak signal based at least in part on the second filtered signal; and

a data detection circuit configured to select a reconstructed data signal based at least in part on the first peak signal and the second peak signal.

9. The isolated ADC circuit of claim 1 , further comprising:

a first modulator configured to generate a first modulated data signal based at least in part on a first bit of a digital data signal and a first digital carrier signal at a first carrier frequency, wherein the first carrier frequency is greater than a frequency of the first single-bit stream;

a second modulator configured to generate a second modulated data signal based at least in part on a second bit of the digital data signal and a second digital carrier signal at a second carrier frequency greater than the first carrier frequency; and

an adder configured to add the first modulated data signal and the second modulated data signal to the first single-bit stream.

10. An analog-to-digital conversion method for an isolated analog-to-digital converter circuit comprising a hot side and a cold side separated from the hot side by a first isolator, comprising:

converting a first analog input signal to a first side multi-bit digital signal using a first multi-bit analog-to-digital converter on the hot side;

modulating the first side multi-bit digital signal to generate a first single-bit stream using a first modulator in the hot side;

transmitting the first single-bit stream from the hot side to the cold side across the first isolator; and

filtering the first single-bit stream from the first isolator to generate a first reconstructed multi-bit digital signal using a first filter on the cold side.

11. The method of claim 10 , wherein transmitting the first single-bit stream from the hot side to the cold side comprises transmitting the first single-bit stream from a first die to a second die.

12. The method of claim 10 , further comprising:

converting, using a second analog-to-digital converter, a second analog input signal to a second multi-bit digital signal;

modulating the second multi-bit digital signal to generate a second single-bit stream;

transmitting the second single-bit stream across a second isolator to a second filter; and

filtering, by the second filter, the first single-bit stream from the second isolator to generate a first reconstructed multi-bit digital signal, wherein the first filter and the second filter are on a common die.

13. The method of claim 10 , further comprising decimating the first side multi-bit digital signal before modulating the first side multi-bit digital signal.

14. The method of claim 10 , further comprising:

receiving a first digital data signal on the hot side;

modulating the first digital data signal to a first digital carrier signal at a first carrier frequency to generate a first modulated data signal, wherein the first carrier frequency is greater than a frequency of the first single-bit stream; and

adding the first modulated data signal to the first single-bit stream on the hot side.

15. The method of claim 14 , further comprising:

modulating the first digital data signal to a second digital carrier signal at a second carrier frequency to generate a second modulated data signal, wherein the second carrier frequency is greater than the first carrier frequency, wherein the second carrier frequency is greater than the frequency of the first single-bit stream; and

adding the second modulated data signal to the first single-bit stream and the first modulated data signal on the hot side.

16. The method of claim 15 , further comprising:

filtering a sum of the first modulated data signal, the second modulated data signal, and the first single-bit stream on the cold side around the first carrier frequency to generate a first filtered signal;

generating a first peak signal indicating at least one peak of the first filtered signal;

filter the sum of the first modulated data signal, the second modulated data signal, and the first single-bit stream on the cold side around the second carrier frequency to generate a second filtered signal;

generating a second peak signal indicating at least one peak of the second filtered signal; and selecting a reconstructed data signal based at least in part on the first peak signal and the second peak signal.

17. The method of claim 10 , further comprising:

modulating a first bit of a digital data signal and a first digital carrier signal to generate a first modulated data signal, wherein a first carrier frequency of the first digital carrier signal is greater than a frequency of the first single-bit stream;

modulating a second bit of the digital data signal and a second digital carrier signal to generate a second modulated data signal, wherein a second carrier frequency of the second digital carrier signal is greater than the first carrier frequency; and

adding the first modulated data signal and the second modulated data signal to the first single-bit stream.

18. An isolated analog-to-digital converter (ADC) circuit, comprising:

a multi-bit ADC at a first side of the isolated ADC circuit, the multi-bit ADC for converting a first analog input signal to a first side multi-bit digital signal, wherein the first side is separated from a second side of the isolated ADC circuit by a first isolator;

means, at the first side, for converting the first side multi-bit digital signal to a first single-bit stream; and

means for receiving the first single-bit stream across the first isolator and generating a first reconstructed multi-bit digital signal using the first single-bit stream.

19. The isolated ADC circuit of claim 18 , further comprising:

means, at a third side of the isolated ADC circuit, for converting a second analog input signal to a second multi-bit digital signal, wherein the third side is separated from the second side by a second isolator;

means, at the third side, for generating a second single-bit stream using the second multi-bit digital signal, and

means, at the second side, for receiving the second single-bit stream across the second isolator and generating a second reconstructed multi-bit signal using the second single-bit stream.

20. The isolated ADC circuit of claim 18 , further comprising:

means for generating a first modulated data signal based at least in part on a digital data signal and a digital carrier signal at a first carrier frequency, wherein the first carrier frequency is greater than a frequency of the first single-bit stream; and

means for adding the first modulated data signal to the first single-bit stream.