Receiver architecture for digital isolators employing notch filters common mode transient immunity

1. A differential receiver circuit comprising:

a band-stop filter having a stopband f SB around a notch frequency f n ; and

a first high-pass filter coupled in series with the band-stop filter, the notch frequency f n being less than a carrier frequency f c of a received signal received by the differential receiver circuit,

wherein the differential receiver circuit is configured to receive the received signal from a differential transmitter via an isolation barrier, the differential receiver circuit having a first voltage domain and the differential transmitter having a second voltage domain.

2. The differential receiver circuit, as recited in claim 1 , wherein the band-stop filter comprises:

a buffer circuit; and

a notch filter coupled in series with the buffer circuit, the notch filter having a stopband around the notch frequency f n .

3. The differential receiver circuit, as recited in claim 1 , wherein the band-stop filter comprises: a passive T-notch filter of resistors having resistance R and capacitors having capacitance C, wherein the notch frequency

f

n

⁢

⁢

is

⁢

⁢

1

2

⁢

π

⁢

⁢

RC

.

4. The differential receiver circuit, as recited in claim 1 , wherein the notch frequency f n is approximately 30 MHz, the stopband f SB is approximately 20 MHz≤f SB ≤40 MHz, and the differential receiver circuit is configured to attenuate a common mode transient pulse having a pulse width τ CMT in a range of approximately 25 ns≤τ CMT ≤50 ns.

5. The differential receiver circuit, as recited in claim 1 , further comprising:

an input stage having a low input impedance, the input stage comprising a common gate differential circuit having a virtual ground at a tail node; and

a second high-pass filter coupled in series with the input stage and the band-stop filter.

6. The differential receiver circuit, as recited in claim 5 , further comprising:

an intermediate gain stage coupled in series with the band-stop filter, the intermediate gain stage comprising a common source differential circuit; and

a third high pass filter coupled in series with the intermediate gain stage.

7. The differential receiver circuit, as recited in claim 6 , further comprising:

a demodulator coupled in series with the third high pass filter, the demodulator being configured to remove a carrier wave from an output of the third high pass filter and generate a recovered digital signal using hysteretic thresholds.

8. The differential receiver circuit, as recited in claim 7 , wherein the demodulator is configured for full-wave rectification of the received signal.

9. The differential receiver circuit, as recited in claim 1 , wherein the differential receiver circuit has a propagation delay independent of a pulse width of common mode transient energy attenuated by the differential receiver circuit.

10. A method of receiving a signal comprising:

band-stop filtering a first version of a received signal to attenuate energy in a stopband f SB around a notch frequency f n ; and

high-pass filtering a second version of the received signal to attenuate energy below a carrier frequency f c of the received signal, the carrier frequency f c being higher than the notch frequency f n ,

wherein the method of receiving has a propagation delay independent of events being attenuated.

11. The method, as recited in claim 10 , wherein the band-stop filtering comprises:

buffering and notch filtering the first version of the received signal, the notch filtering attenuating energy in a second stopband around the notch frequency f n .

12. The method, as recited in claim 10 , wherein the notch frequency f n is approximately 30 MHz, the stopband f SB is approximately 20 MHz≤f SB ≤40 MHz, and the energy includes a pulse having a pulse width τ CMT in a range of approximately 25 ns≤τ CMT ≤50 ns.

13. The method, as recited in claim 10 , further comprising:

demodulating the received signal to generate a demodulated received signal; and

recovering digital data from the demodulated received signal using hysteretic thresholds.

14. The method, as recited in claim 10 , further comprising:

transmitting a control signal across an isolation barrier using a transmitter having a first voltage domain; and

receiving the control signal as the received signal by a receiver having a second voltage domain.

15. A differential receiver comprising:

a first circuit configured to attenuate energy in a first frequency range of a frequency response of a received signal, the first frequency range being f≤f c , where f is frequency and f c is a carrier frequency of the received signal;

a second circuit coupled in series with the first circuit and configured to attenuate energy in a second frequency range of the frequency response of the received signal, the second frequency range being f n /k≤f≤(2×k×f n ), where f n is a notch frequency of a notch filter included in a band-stop filter having a stopband around the notch frequency and k is a scaling factor; and

a third circuit coupled in series with the second circuit and configured to remove a carrier wave from an output of the second circuit and recover digital data encoded in the received signal using hysteretic thresholds.

16. The differential receiver, as recited in claim 15 , wherein the second circuit includes a buffer coupled in series with the notch filter.

17. The differential receiver, as recited in claim 15 , wherein the third circuit includes a demodulator configured to use the hysteretic thresholds for recovery of on-off keying modulated signals generated using the carrier wave.

18. The differential receiver, as recited in claim 15 , wherein the differential receiver has a propagation delay independent of a pulse width of common mode transient energy attenuated by the differential receiver.