Isolation communications channel using direct demodulation and data-edge encoding

Patent metadata

Field	Value
Publication number	US-11689174-B2
Application number	US-202117335839-A
Country	US
Kind code	B2
Filing date	Jun 1, 2021
Priority date	Jun 1, 2021
Publication date	Jun 27, 2023
Grant date	Jun 27, 2023

Abstract

An apparatus for communicating across an isolation barrier includes a differential pair of input terminals. The apparatus includes a bandpass filter circuit configured to receive a received signal on the differential pair of input terminals and to provide a received differential signal on a differential pair of nodes. The apparatus includes a demodulator directly coupled to the bandpass filter circuit and configured to directly demodulate the received differential signal on the differential pair of nodes to provide a demodulated received signal.

First claim

What is claimed is:

1. An apparatus for communicating across an isolation barrier, the apparatus comprising:
a differential pair of input terminals;
a bandpass filter circuit configured to receive a received signal on the differential pair of input terminals and to provide a received differential signal on a differential pair of nodes;
a demodulator directly coupled to the bandpass filter circuit and configured to directly demodulate the received differential signal on the differential pair of nodes to provide a demodulated received signal; and
a transmitter path including an oscillator circuit configured to provide an oscillating signal to a differential pair of output terminals in response to a control signal, wherein the bandpass filter circuit includes a first inductor and a first capacitor matched to a second inductor and a second capacitor of the oscillator circuit.

2. The apparatus of claim 1 wherein the bandpass filter circuit is configured to amplify a first frequency band of the received signal and to attenuate a second frequency band of the received signal, a carrier signal of the received signal being in the first frequency band and common-mode transient interference of the received signal being in the second frequency band.

3. The apparatus of claim 1 wherein the demodulator includes a differential pair of transistors, each transistor of the differential pair of transistors having a corresponding source terminal coupled to a corresponding node of the differential pair of nodes.

4. The apparatus of claim 1 , further comprising a digital circuit configured to provide a received digital signal based on the demodulated received signal, the digital circuit being configured to toggle the received digital signal to a first logic value in response to a pulse of the demodulated received signal having a first width and configured to toggle the received digital signal to a second logic value in response to a second pulse of the demodulated received signal having a second width.

5. The apparatus of claim 1 ,
further comprising:
the oscillator circuit coupled to the differential pair of output terminals and configured to transmit a signal using the differential pair of output terminals according to a transmit data signal received on a center tap of the second inductor of the oscillator circuit; and
a control circuit configured to generate the transmit data signal having a first modulated pulse with a first pulse width in response to a first transition of an input data signal and to generate a second modulated pulse having a second pulse width in response to a second transition of the input data signal, the first pulse width being greater than the second pulse width.

6. An apparatus for communicating across an isolation barrier, the apparatus comprising:
a differential pair of input terminals;
a bandpass filter circuit configured to receive a received signal on the differential pair of input terminals and to provide a received differential signal on a differential pair of nodes;
a demodulator directly coupled to the bandpass filter circuit and configured to directly demodulate the received differential signal on the differential pair of nodes to provide a demodulated received signal, the demodulator including a differential pair of transistors, each transistor of the differential pair of transistors having a corresponding source terminal coupled to a corresponding node of the differential pair of nodes; and a reference transistor having a first size greater than a sum of second sizes of transistors of the differential pair of transistors.

7. The apparatus of claim 6 further comprising a transmitter path including an oscillator circuit configured to provide an oscillating signal to a differential pair of output terminals in response to a control signal, the bandpass filter circuit including a first inductor and a first capacitor matched to a second inductor and a second capacitor of the oscillator circuit.

8. The apparatus of claim 6 wherein an offset threshold of the demodulator is determined by a ratio of the first size of the reference transistor and a second size of each transistor of the differential pair of transistors.

9. The apparatus of claim 6 wherein the demodulator further includes:
a first resistor coupled between a common node coupled to a first source terminal of the reference transistor and a second source terminal of a first transistor of the differential pair of transistors; and
a second resistor coupled between the common node and a third source terminal of a second transistor of the differential pair of transistors, the first resistor and the second resistor having the same resistance.

10. The apparatus of claim 6 wherein the demodulator further includes a bias transistor having a first gate terminal coupled to second gate terminals of the differential pair of transistors and a third gate terminal of the reference transistor.

11. The apparatus of claim 6 wherein the bandpass filter circuit is configured to amplify a first frequency band of the received signal and to attenuate a second frequency band of the received signal, a carrier signal of the received signal being in the first frequency band and common-mode transient interference of the received signal being in the second frequency band.

12. The apparatus of claim 6 , further comprising a digital circuit configured to provide a received digital signal based on the demodulated received signal, the digital circuit being configured to toggle the received digital signal to a first logic value in response to a pulse of the demodulated received signal having a first width and configured to toggle the received digital signal to a second logic value in response to a second pulse of the demodulated received signal having a second width.

13. The apparatus of claim 6 , further comprising:
an oscillator circuit coupled to a differential pair of output terminals and configured to transmit a signal using the differential pair of output terminals according to a transmit data signal received on a center tap of an inductor of the oscillator circuit; and
a control circuit configured to generate the transmit data signal having a first modulated pulse with a first pulse width in response to a first transition of an input data signal and to generate a second modulated pulse having a second pulse width in response to a second transition of the input data signal, the first pulse width being greater than the second pulse width.

14. A method for communicating across an isolation barrier, the method comprising:
bandpass filtering a received signal on a differential pair of input terminals to provide a received differential signal on a differential pair of nodes;
directly demodulating the received differential signal on the differential pair of nodes to provide a demodulated received signal;
selectively configuring a first instantiation of an LC circuit on a first integrated circuit die as an LC oscillator circuit; and
selectively configuring a second instantiation of the LC circuit on a second integrated circuit die as a bandpass filter circuit.

15. The method of claim 14 wherein directly demodulating comprises:
biasing a differential pair of transistors;
receiving the received differential signal on first source terminals of the differential pair of transistors; and
generating an indication of a difference between a first voltage on drain terminals of the differential pair of transistors to a second voltage on a drain of a reference transistor.

16. The method of claim 14 , further comprising:
decoding a first value of a dig

Assignees

• Skyworks Solutions Inc

Inventors

• Zhan Huanhui
• Pentakota Krishna

Classifications

• H04B1/40 Primary

  Circuits · CPC title

• H03B5/1212

  the amplifier comprising a pair of transistors, wherein an output terminal of each being connected to an input terminal of the other, e.g. a cross coupled pair · CPC title

• H03H7/0115 Primary

  comprising only inductors and capacitors (H03H7/075, H03H7/09, H03H7/12, H03H7/13 take precedence) · CPC title

• H03H7/425

  Balance-balance networks · CPC title

• H03B5/12

  active element in amplifier being semiconductor device (H03B5/14 takes precedence) · CPC title