Wide common-mode range receiver

Patent metadata

Field	Value
Publication number	US-9467310-B2
Application number	US-201213457213-A
Country	US
Kind code	B2
Filing date	Apr 26, 2012
Priority date	Apr 26, 2012
Publication date	Oct 11, 2016
Grant date	Oct 11, 2016

Abstract

A wide common-mode range receiver includes an input module, voltage level shift module, voltage level shift control module, and output module. The receiver can also include an equalizer. The receiver translates data originating from a circuit powered from an external voltage supply to a circuit powered by an internal voltage supply. The voltage level shift may be scaled based on differences between the voltage supplies or by determining the difference between an input common-mode voltage and a reference voltage, and driving a servo based on the difference.

First claim

What is claimed is:

1. A common-mode receiver comprising:
an input circuit configured to receive a first input signal and a second input signal, wherein the first and second input signals are associated with a first common-mode voltage;
a voltage level shift circuit operatively coupled to the input circuit and comprising:
a first current source operatively coupled to a first output of the input circuit, wherein the first current source is controlled by a control signal, and
a second current source operatively coupled to a second output of the input circuit, wherein the second current source is controlled by the control signal; and

a control circuit operatively coupled to the voltage level shift circuit, and configured to receive the first common-mode voltage and generate the control signal based at least in part on a magnitude of a current induced by a difference between the first common-mode voltage and a reference common-mode level,
wherein the voltage level shift circuit is configured to:
shift a voltage level of the first input signal and the second input signal based at least in part on the control signal, wherein the voltage level is shifted in proportion to the magnitude of the current induced by the difference between the first common-mode voltage and the reference common-mode level, and
output a first output signal based at least in part on the shifted voltage level of the first input signal and a second output signal based at least in part on the shifted voltage level of the second input signal, wherein the first and second output signals are associated with an output common-mode level.

2. The common-mode receiver of claim 1 , further comprising:
a first node formed between a first switching element of the voltage level shift circuit and the first current source; and
a second node formed between a second switching element and the second current source, wherein the first node and the second node form a virtual ground with respect to the first common-mode voltage.

3. The common-mode receiver of claim 2 , wherein the first node is operatively coupled to an emitter of a BJT of the first switching element and a drain of a FET of the first current source.

4. The common-mode receiver of claim 3 , wherein the second node is operatively coupled to an emitter of a BJT of the second switching element and a drain of a FET of the second current source.

5. The common-mode receiver of claim 4 , further comprising a third node operatively coupled to a base of a BJT of the first switching element, a base of a BJT of the second switching element, and a base of a BJT of one or more control switching elements of the control circuit.

6. The common-mode receiver of claim 1 , wherein the control circuit comprises:
a cascode circuit,
a current mirror operatively coupled to the cascode circuit, and
a control current source operatively coupled to the current mirror, the first current source, and the second current source,
wherein an output of the current mirror and an output of the cascode circuit provide the control signal to the control current source, the first current source, and the second current source.

7. The common-mode receiver of claim 6 , wherein an input to the control circuit provides a current to the cascode circuit.

8. The common-mode receiver of claim 6 , further comprising a first control node operatively coupled to an emitter of a BJT of one or more control switching elements of the control circuit and a drain of a FET of the control current source.

9. The common-mode receiver of claim 8 , further comprising a second control node operatively coupled to a collector of a BJT of the one or more control switching elements and the source a source of a FET of the cascode circuit.

10. The common-mode receiver of claim 6 , wherein the cascode circuit comprises one or more FETS and the current mirror comprises one or more FETS.

11. The common-mode receiver of claim 6 , wherein a third node is coupled to a drain of a FET of the cascode circuit, a drain of a FET of the current mirror and a gate of a FET of each of the first current source, the second current source, and the control current source.

12. The common-mode receiver of claim 1 , wherein an input to the control circuit comprises a higher impedance than an input to the input circuit.

13. The common-mode receiver of claim 1 , wherein a differential component of the first and second output signals is scaled from a differential component of the first and second input signals.

14. A common-mode receiver comprising:
an input circuit configured to receive at least a first input signal and a second input signal;
a voltage level shift circuit operatively coupled to the input circuit and configured to apply a level shift to the first input signal and the second input signal and generate a first output signal that is level shifted from the first input signal and a second output signal that is level shifted from the second input signal based at least in part on a control signal, wherein a magnitude of the level shift varies in relation to a current induced by a difference between a common-mode voltage of the first input signal and the second input signal and a reference common-mode level; and
a voltage level shift control circuit operatively coupled to the voltage level shift circuit and configured to:
receive the first input signal and the second input signal, and
generate the control signal based at least in part on a magnitude of the current induced by the difference between the common-mode voltage and the reference common-mode level.

15. The common-mode receiver of claim 14 , wherein the voltage level shift circuit comprises:
a first current source configured to control a first current through the voltage level shift circuit based at least in part on the control signal, and
a second current source configured to control a second current through the voltage level shift circuit based at least in part on the control signal.

16. The common-mode receiver of claim 15 , wherein the voltage level shift control circuit comprises a cascode circuit and a current mirror.

17. The common-mode receiver of claim 16 , wherein the voltage level shift control circuit comprises a control current source configured to receive the control signal, and wherein the control signal for the control current source, the first current source, and the second current source corresponds to an output of the current mirror and an output of the cascode circuit.

18. The common-mode receiver of claim 14 , wherein voltage level shift control circuit comprises a control current source configured to receive the control signal and sink the current induced by the difference between the common-mode voltage and the reference common-mode level based at least in part on the received control signal.

19. A method for performing a voltage-level shift at a common-mode receiver, the method comprising:
receiving a first input signal and a second input signal at an input circuit, wherein the first input signal and the second input signal are associated with a first common-mode voltage;
receiving the first input signal and the second input signal at a control circuit; generating a control signal at the control circuit based at least in part on a magnitude of a current induced by a difference between the first common-mode voltage and a reference common-mode level;
receiving the control signal at a voltage level shift circuit; and
applying, at the voltage level shift circuit and based at least in part on the control signal, a

Assignees

• Bankman Jesse
• Lu Quanli
• Tam Kimo
• Analog Devices Inc

Inventors

• Bankman Jesse
• Lu Quanli
• Tam Kimo

Classifications

• H03F3/50

  Amplifiers in which input is applied to, or output is derived from, an impedance common to input and output circuits of the amplifying element, e.g. cathode follower · CPC title

• H03F2200/453

  Controlling being realised by adding a replica circuit or by using one among multiple identical circuits as a replica circuit · CPC title

• H04L25/0274 Primary

  Arrangements for ensuring balanced coupling · CPC title

• H03F2203/45306

  the common gate stage implemented as dif amp eventually for cascode dif amp · CPC title

• H04L25/0296

  Arrangements to ensure DC-balance · CPC title